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E36313A Triple Output DC P.S. - Review

Scoring

Product Performed to Expectations: 8
Specifications were sufficient to design with: 10
Demo Software was of good quality: 10
Product was easy to use: 10
Support materials were available: 10
The price to performance ratio was good: 10
TotalScore: 58 / 60
  • RoadTest: E36313A Triple Output DC P.S.
  • Buy Now
  • Evaluation Type: Power Supplies
  • Was everything in the box required?: No - I received a unit which was configured for a 115V mains supply and it was supplied with a US power cord. Being in the UK I have a 230V mains supply and our plugs are very different. This is not a problem as there are switches on the back to configure the voltage and I have other power cables available.
  • Comparable Products/Other parts you considered: There are numerous power supplies available from all the main test equipment manufacturers. The most direct comparison product I have available is a TTi QL335T or alternatively I have a TTi PL303QMD + TTi CPX400S combo, both of these solutions would give comparable triple PSU outputs.
  • What were the biggest problems encountered?: The unit being shipped with the wrong configuration but this isn't really a problem as it's easy to solve. I have found that there is an audible mains hum from my unit regardless of whether the supply is turned on or off, for as long as the AC inlet is powered. From searching online I found that whilst most people report the unit to be extremely quiet, there are some people who have units which make a mains hum the same as my unit. I reported the issue to Randall and he contacted Keysight who have sent me an email this morning confirming that this is not normal for these units and they are going to send me a replacement unit and arrange for my current one to be collected so they can investigate the issue. This is excellent service from Element14/Keysight.

  • Detailed Review:

    1. Introduction

    1.1. Overview

     

    I received my shiny new Keysight E36313A Power Supply from Element14 this week. Thank you so much to both Element14 and Keysight for picking me for this Road Test. It's an excellent product and I am very happy indeed to have one sitting in my lab. I have a pretty good setup already but my current PSU's are missing a few really useful features which the Keysight unit happily provides.

     

    This Power Supply is the top of the range model from the Keysight E36300 range. There are three models currently available, the entry level E36311A which is limited to 80W total power output and has a limited feature set, and the fully featured E36312A and E36313A models which have all the features enabled but with 80W and 160W total output power respectively. These models can also optionally have a GPIB interface which is supplied in my review unit. Unfortunately I do not have any way to utilize GPIB currently, but as the unit also has USB and Ethernet this is no problem at all. The main differentiations between the available features for the three models is shown in the image* below:

     

     

    * Taken from the Keysight E36313A Bench Power Supply Data Sheet

     

    1.1.1. External Links

     

    Keysight E36300 Triple Output Bench Power Supply Data Sheet: http://literature.cdn.keysight.com/litweb/pdf/5992-2124EN.pdf

     

    1.2. What's in the Box?

     

    The unit came very well packed in a sturdy box and held firmly in place within the box with custom packaging. Inside the box was the E36313A itself and a small box containing the following additional items:

     

    • US Power cable - This was a mistake as I was shipped a unit intended and configured for the US market. More about this below.
    • A bag containing 1 x 4-way 3.81mm terminal plug, 1 x 4-way 5.08mm terminal block plug, and 1 x 8-way 5.08mm terminal plug. These are to connect to the rear panel I/O connectors. More about this below.
    • A bag containing 1 x Keysight Instrument Control DVD. This contains the IO Libraries 2017 Update 1, Command Expert 2017 Update 1, and the BenchVue 2017 suite.
    • An envelope containing the Certificate of Calibration for the unit.
    • Various additional pieces of documentation, e.g. Packing List, Quick Start, Safety Information, etc

     

    1.3. The Main Specifications

     

    The main specifications for the three versions available of the Keysight E36300 Bench Power Supplies shown in the image* below:

     

    * Taken from the Keysight E36313A Bench Power Supply Data Sheet

     

    1.4. Comparable Solutions

     

    For this road test I am going to be evaluating the Keysight E36313A and comparing it to two other solutions I have available to me:

     

    1. TTi QL355T - Like the Keysight, this is a triple output unit.
    2. TTi PL303QMD + TTi CPX400S combo - In order to have the same three outputs I could combine two other power supplies. In this case my dual output TTi PL303QMD and my single output TTi CPX400S units.

     

    SpecificationKeysight E36313A

    TTi QL355T

    TTi QL355TP

    TTi PL303QMD

    TTi PL303QMD-P

    TTi CPX400S

    TTi CPX400SP

    Price*

    * As on Farnell UK 18/12/2017

    £1317.00 + VAT

    £760.00 + VAT

    £947.00 + VAT

    £529.00 + VAT

    £707.00 + VAT

    £558.00 + VAT

    £717.00 + VAT

    DC Output Ratings

    Channel 1: 0 to 6V @ 0 to 10A

    Channel 2: 0 to 25V @ 0 to 2A

    Channel 3: 0 to 25V @ 0 to 2A

    Channel 2||3: 0 to 25V @ 0 to 4A

    Channel 2+3: 0 to 50V @ 0 to 2A

    Channel 1: 0 to 15V @ 0 to 5A / 0 to 35V @ 0 to 3A / 0 to 35V @ 500mA

    Channel 2: 0 to 15V @ 0 to 5A / 0 to 35V @ 0 to 3A / 0 to 35V @ 500mA

    Channel 3: 2.7V @ 0 to 1A / 3.3V @ 0 to 1A / 5V @ 0 to 1A

    Channel 1: 0 to 30V @ 0 to 3A

    Channel 2: 0 to 30V @ 0 to 3A

    Channel 1||2: 0 to 30V @ 0 to 6A

    0 to 60V @ 0 to 20A (Max 420W TPD)
    Max Total Power160W110W180W420W
    Operating Modes

    Independent, Tracking, Series*, Parallel*

    * Fully automatic connection and control

    Independant, Linked*, Tracking

    * Enables linked controls with manually configured series / parallel modes

    Independant, Tracking, Series*, Parallel*

    *Series with manual connection in Tracking mode,

    Parallel is configured internally with a switch on the front panel.

    Independant
    Load Regulation - Voltage< 0.01% + 4 mV

    Channel 1: < 0.01% + 2 mV

    Channel 2: < 0.01% + 2 mV

    Channel 3: < 1.0% for a 90% load change

    Channel 1:

    Channel 2:

    < 0.01%
    Load Regulation - Current< 0.01% + 500 uA

    Channel 1: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range)

    Channel 2: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range)

    Channel 3: < 1.0% for a 90% load change

    Channel 1:

    Channel 2:

    < 0.05%
    Line Regulation - Voltage< 0.01% + 1 mV

    Channel 1: < 0.01% + 2mV for a 10% line change

    Channel 2: < 0.01% + 2mV for a 10% line change

    Channel 3: < 0.1% for a 10% line change

    Channel 1:

    Channel 2:

    < 0.01% for a 10% line change
    Line Regulation - Current< 0.01% + 500 uA

    Channel 1: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range)

    Channel 2: < 0.01% + 250uA (5A/3A range), < 0.01% + 50uA (500mA range)

    Channel 3: < 0.1% for a 10% line change

    Channel 1:

    Channel 2:

    < 0.01% for a 10% line change
    Output Ripple

    Channel 1: < 350 uVrms / 2 mVpp

    Channel 2: < 1 mVrms / 5 mVpp

    Channel 3: < 1 mVrms / 5 mVpp

    Channel 1: < 350 uVrms / 2 mVpp

    Channel 2: < 350 uVrms / 2 mVpp

    Channel 3: < 1 mVrms typical

    Channel 1:  < 400 uVrms / 2 mVpp

    Channel 2: < 400 uVrms / 2 mVpp

    < 3 mVrms / 15 mVpp
    EthernetYesNoYes (P version)Yes (P version)
    USBYesYes (P version)Yes (P version)Yes (P version)
    GPIBYesYes (P version)Yes (P version)Yes (P version)
    RS-232NoYes (P version)Yes (P version)Yes (P version)

     

    So we can see from the above whilst the solutions are comparable in some respects, there are differences which may make one solution or another a better fit for certain applications. For example, the combination of the TTi PL303QMD-P and the TTI CPX400SP give a massive total power capability of 600W between the two which for some higher power applications may be an advantage.

     

    However, it should be noted that it's not all about the fine detail of the specs, a huge factor for a general purpose lab power supply is the ease of use and its ability to be well integrated into an overall test solution. We can see from the above that making various configurations for the output power rails is much simpler with the Keysight as all the connections as well as the combining of controls is all handled internally to the power supply with no additional wiring necessary.

     

    3. First Look at the Unit

    3.1. Front Panel Overview

     

    Looking at the image to the left we can see the unit has a fairly simple layout. There is a large screen to the left with size buttons immediately below it in a row.

     

    To the right there is a section with two rotary knobs, one to control the voltage and one to control the current. Above these are three colour coded buttons to select which of the three output channels is selected for control. Immediately below these are some navigation and control buttons plus a numeric keypad.

     

    Across the bottom of the unit you can see the binding posts for all three outputs. These are also colour coded and you can see they match the colour coding of the buttons at the top and their individual output enable buttons. It should be noted that, although you can't see here, the coloured buttons illuminate when the unit is powered on.

     

    To the left of the screen there is a USB port to enable a flash drive to be connected.

     

    Last but not least at the bottom left hand side of the front panel we find the soft touch power button and it's associated power on LED.

     

    3.2. Rear Panel Overview

    From the image to the left we can see that the rear panel of the unit is quite well utilized, there certainly isn't much room to add anything else! A large area in the middle is taken up by a vent for a cooling fan. I've heard this fan spin up a little during startup but not much at other times. Maybe once I get into testing this unit under higher load the fan will kick in and become more noticeable but generally the fan itself is very quiet. I'll touch on the noise levels from the unit a little bit more below.

     

    At the top left there is an 8-way 5.08mm terminal block connector for connecting to Output Channel 2 and Output Channel 3 of the power supply. Note that this provides four pins per supply output.

     

    Working our way down, we find an earth stud and then down at the bottom another 4-Way 5.08mm terminal block connector, this time for connecting to Output Channel 1 of the power supply. Again, note that this provides 4 pins for the supply output.

     

    At the top right we have the LAN connector and the USB connector. This USB port would be used to connect to a computer to allow the instrument to be controlled over USB. In my case I will be using Ethernet for my control interface so this will not be required. It should be noted that there was NOT a USB or Ethernet cable supplied with the unit and I think for a unit in this price bracket these should definitely be supplied. Fortunately after a short rummage in a drawer I managed to dig out a spare Ethernet cable so my review did not come to a screeching halt at that point.

     

    At the bottom right you will see the power inlet. At this point I should mention that I am based in the UK. The eagle eyed amongst you may notice there is something amiss noted on the back of this unit. You can see that the 115V configuration marking is shown. This unit was actually shipped to me configured for the US market and as such was set up for 115V rather than the 230V we use in this country. Fortunately I saw this before plugging in and powering up the unit otherwise I expect I would be requiring a replacement.

    The unit is easily configurable to support different voltages. As you can see there is a table on the back showing the switch positions for 100V, 115V, and 230V. In my case I simply needed to slide the right hand switch over from the left to the right to change it to the correct setting. Below is a close up on this section of the rear panel to give a clearer view of the configuration switches. So, a small disaster has been averted and I can get on with reviewing my unit!

     

     

    4. Getting More Familiar with the Unit

    4.1. Teardown!

     

    In the words of Dave Jones from the EEVBlog (like you didn't know who he was?!), don't turn it on, take it apart!

     

    Okay so I'm not Dave Jones, or any of those that get given lots of free kit with the explicit expectation they'll tear it down. I'm not going to totally strip the unit down into as many pieces as I can get it into now because I don't want to risk accidentally damaging the unit and I really like this unit and want to be able to use it as my main lab power supply so I am not going to do anything to risk breaking it. If Keysight would like to send me a faulty unit they have lying around, I would be more than happy to do a more detailed tear down of that at a later date, but for now I'm just going to pop the lid and take a few pics of the insides. It's quite easy to get the lid off if you have a Torx driver set as it is held in place by two Torx bolts on each side and two on the top at the back. Once these are removed the lid simply slides out backwards.

     

    4.1.1 The Main Board

     

    Unfortunately I am being very cautious so this is the best view I can get of the main board without taking the unit apart further and looking at what, if anything is located on the other side. I can see some residue on the board so it's not been quite as well cleaned in production than I would have liked but it's probably no-clean flux so not going to be causing any issues.

     

    You an see a few features of this board, for example there are two separate diode bridge's taking the secondary AC and then converting to various DC levels. There appear to be regulators for +12V and -12V, +3V3, +2V5, some current monitoring and towards the bottom I can see circuitry relating to the constant current and constant voltage references.

    4.1.2. Front Panel Controller Board

     

    You can see inside here, it's a typical embedded processor board. The main processor which controls the unit is shown and we can see it's all running on an STM32. You can make out a few other pieces of circuitry, some local power supplies, clocks, the FPC ribbons which go to the LCD and a coin cell battery presumably for an RTC or for a hold-up on some memory being used to store settings. I'd go for it being for an RTC as these days there are lots of options for non-volatile storage for small data sets like settings which are really cost effective and don't require an external hold up supply.

    4.1.3. A Deep Dark View into the Back!

     

    There is not a lot else to say about this one, I tried to shine some light in to the back to try and illuminate what was there, but unfortunately there is just too much in the way. You can just about make out that there is another board at the bottom of the unit, running across the back.

     

     

     

     

     

     

    4.2. A Run Down of the User Interface

     

    We can see from the image on the left that the unit has a very clear full colour LCD. The firmware uses appropriate colour coding for each of the channels which ties in with the colour coding for the buttons and the terminal post surrounds. This all ties the various displays and the physical controls together nicely and makes it very easy to quickly see for which channel you are viewing or editing the settings.

     

    Along the bottom of the LCD there is an area reserved for button labels. This area is fixed and there is one segment for each of the physical buttons which reside immediately below the LCD. The labels help guide you through the various options and update to be specific for each page you are viewing.

     

    Editing the settings for a particular channel is a simple matter of pressing a button to get to the control page for the currently selected channel. From there you can use the navigation buttons to move to each of the various options, you can type values in on the numeric keypad, or you can use the voltage and current knobs to make fine adjustments quickly. For setting a specific voltage or current it is almost always easier just to dial it in on the keypad than to try to use the knobs.

     

    Across the bottom there are four buttons, three of these are colour coded channel output enable buttons as previously described and the fourth is a button dedicated to turning all the channels on or off at the same time.

    4.2. Delving into the Usability

     

    So the big question is, how well does this interface work for every day usage scenarios. Well, I've only had it a couple of days so haven't used it extensively at all yet but it seems very intuitive to use. The combination of a simplified single set of controls to operate all three channels, the colour coding and the very large and clear colour LCD give a good foundation for a easy to operate unit. Lets now take a short tour around a few of the menus to see how we'd go about setting up the unit to perform a few basic tasks. We'll do this by way of some examples which we will work through to show the various steps required.

     

    So before we get into the actual setups, I wanted to show you a image of the main screen and show a little glitch I found when using the web interface (we'll look at this later) to grab images from the screen.

     

     

    Looking at the two images above, these are both of the main LCD screen when it just has the default configuration of 0V and maximum current set up on all it's outputs.

     

    If you look carefully you will see that on the first image there is a glitch in the current reading for both channel 1 and channel 2. These are reading exceedingly small values, in the order of <10uA and there is naturally some noise on these readings. However, you'd expect the capture to grab a stable image. It would appear rather than the capture grabbing the currently stable display buffer it is grabbing a buffer that is the subject of the next display update. I don't know if the rendering to the display itself is double buffered or not, although I haven't seen any tearing on the display which is the usual sign of updates happening on the live display, but this issue with the screen capture is something to watch out for if you are grabbing images for a report. It means rather than working through quickly and grabbing all the images you need as you go, you have to switch to another window and check the grabbed image and recapture if necessary. I hope Keysight fix this issue soon!

     

    In the screen captures you can see the information about each channel which is displayed, i.e. The set voltage and current, the actual measured voltage and current, whether a 2-Wire or 4-Wire connection is used, and whether the channel is turned on or off. If I now press the Channel 1 select button again the display will change to give more detailed information for Channel 1 as shown below.

     

     

    We can see that the Channel 1 area has now expanded to take up 2/3 of the display area with the Channel 2 and Channel 3 displays being condensed to show only their measured voltage and current and stacked on top of each other.

     

    With this configuration the display shows a lot more information about the channel setup including over-current and over-voltage protection settings (OCP and OVP) as well as any delay settings relating to the OCP and also for turning the output On/Off.

     

    Finally we see it now also displays the measured power in W too which is a really nice feature which should speed up things like generating efficiency curves for DC-DC converters (especially if I had a Keysight Bench DMM with a similar feature!) or checking the power consumption of a circuit quickly in various operating states.

     

    Above I made a brief comment about showing whether 2-Wire or 4-Wire output modes are being used. In case you are not familiar with this terminology, I will explain further now.

     

    • 2-Wire simply means that only the + and - outputs of the PSU go directly to the load which means that depending on the load and the cables used there may be a significant voltage drop in the cables and the voltage measured at the supply output may not be what is presented to the load.
    • 4-Wire connections use an additional pair of wires as a "sense" connection. These carry no significant current so they measure the exact voltage at the load. This measurement is then used to adjust the powers supply output to compensate for the voltage drop in the cables to ensure the load sees the intended voltage. Please note: If you set 4-Wire and your sense wires aren't connected with some supplies it is possible to significantly over-voltage the load. I'll take a look at how this supply deals with this scenario in due course.

     

    Those with eagle eyes (or generally anybody who has got this far and been paying attention!) will notice that the front panel doesn't have the capability available for 4-Wire connections. If you wish to use this mode of operation then you will need to make some cables up with the supplied terminal plugs and use the rear panel connectors.

     

    4.2.1. Set Channel 1 to 5V with a 2.5A current limit.

     

     

    We're starting from a clean slate with this so currently all the channels are set up with the default configuration so we can see that Channel 1 is the selected channel and is currently set to 0 Volts @ 10 Amps. In order to configure the voltage and current for this channel we simply press the button below the 'Source Settings' label to get to the source configuration screen for Channel 1.

     

    Once in the 'Output 1 - Source Settings' screen we can see that there are a number of things that can be configured beyond just the basic voltage and current.

     

    We can configure the various protection thresholds for over voltage (OVP) and over current (OVP) and we can configure delays for the over current protection. You'll notice that for the over current there are two possible delays, 'OCP Delay Start' and 'OCP Delay'. The reason for a separate start delay is so that during power up, where there is likely to be a significant inrush current we can increase the delay before the OCP trips to allow the system to power up correctly, but then once it's up and running we can introduce a faster OCP trip if desired. For our example we aren't looking at OVP and OCP so we'll leave these settings at their default values.

     

    We can also choose between 2-Wire and 4-Wire connections in this screen. We'll be using the front panel connectors so we're going to leave the default 2-Wire setting.

     

    Using the Up/Down/Enter buttons and the numeric pad we can now go ahead and enter the values for the desired output voltage and current limit.

     

    Once everything has been set up the resulting screen should be as shown to the left.

     

    Once we return to the main screen we can see that our new settings for Channel 1 are shown in the 'Set' boxes at the bottom of the Channel 1 display area.

     

    You might have noticed that Channel 2 is now selected. This is because I selected this channel to move onto the next set of tests before I remembered to save the screenshot. It's not some random mode change or anything odd like that, it's just me almost forgetting to grab what I needed for this report.

     

    4.2.2. Set Channel 2 and 3 to provide +9V and -9V rails which are tied together and tracking each other with a 1A current limit.

     

    The same procedure as we used for Channel 1 above will be used for setting the desired voltage and current for channel 2. It's all very quick and intuitive to get set up and it would be very difficulte to get it wrong. If you try and set a voltage or current which is out of range it will tell you and there is visual feedback at every step at to what changes have been made.

     

    Here I have configured Channel 2 to be 9V with a current limit of 1A.

     

    Returning to the main screen we can see Channel 2 has the correct settings, but at the moment Channel 3 is not set up.

     

    At this point we need to press the button below the 'Output Settings' label to take us to the configuration screen which will allow us to configure the modes available.

     

    On this screen we can configure various options, On/Off delays, On/Off coupling, Inhibits and also the mode of operation.

     

    For these examples we will ignore the delays, coupling, and inhibits and we'll come back to these later. For now we will look purely at the 'Operation Mode' option which allows us to select between four different modes as described in the next section.

     

    If we press the button below the 'Operation Mode' label we will move to the screen below.

     

    Here we can see several pieces of information:

     

    1. Down the right hand side is a summary of the current output settings.
    2. A large picture and description is shown in the main section which gives a picture of what is available at the various outputs along with information about exactly what is available from the various connections shown.

     

    Along the bottom the button labels have changed to show the various possible modes:

     

    • Independent - The outputs are completely independent and can be set to any valid value for each output.
    • Series - The outputs are internally connected in series with the output voltage being across the positive pin of Channel 2 and the negative pin of  Channel 3.
    • Parallel - The outputs are internally connected in parallel with the output voltage being available on the Channel 2 output pins.
    • Tracking - Channel 3 is set to track the settings of Channel 2 so anything that happens to that channel will be reflected on Channel 3.

     

    We want the outputs to track each other because we want a +/-9V set of power rails. In this case we've pressed the button below the 'Mode Tracking' label.

     

    The picture and description below show us what is now available from the Channel 2 and Channel 3 outputs.

     

    Pressing the 'Back' button we return to the main screen and can see that Channel 3 has now changed to show 9V as it is tracking Channel 2.

     

    One thing to be wary of is that only the voltage setting is reflected when choosing tracking. I think it would be useful to be able to set the current limit based on the tracked channel too, this could avoid some annoying mistakes. It's always good to check these things before applying power, fortunately the way this information is presented with this unit makes it really easy and quick to spot these kinds of things.

     

    We can correct the output current limit for Channel 3 by setting it in the same way we did for Channel 1 and Channel 2.

     

    To the left we can see the result of setting the current on the 'Source Setting' screen for Channel 3.

     

    Finally on the main page we can see that out outputs have now been correctly configured.

     

    In order to achieve the +/-9V which we desire on the output we shall externally connect the positive of Channel 3 to the negative of Channel 2 and use this also as the 0V reference for our circuit. Channel 2 will now be our +9V supply and Channel 3 will now be our -9V supply.

     

    4.2.3. Set Channel 2 and 3 to produce a single 48V rail with a 0.5A current limit.

     

    In this setup we are going to be configuring the power supply to put Channel 2 and Channel 3 is series mode. This allows double the maximum output voltage of any one of these two channels. Of course we could do this with most decent bench power supplies with floating output channels simply by tying the positive of one channel to the negative of the other.

     

    The beauty of the Keysight E36313A though is that connecting the outputs in series or parallel mode is all done internally so it gets configured correctly and doesn't rely on any external wiring which could be a point of failure (or mistake) in a test set up. Also in these modes, the main controls of channel 2 directly control the output voltage so no need to mess about setting multiple voltages and current limits. Simply set it how you want it as if it's a single power supply channel with those specs.

     

    So when I did these setups, my head was in the usual mindset for setting up series outputs manually. In this case I set Channel 2 to be 24V at 0.5A first, intending to have to go and do this with Channel 3 also but once I had done this and selected 'Mode Series' below, I soon realised this wasn't necessary!

     

    In the output setting window we can how choose 'Mode Series'. It will update the page to show how to connect to the supply in this instance and the limits of the combined channels. In this case we effectively have a single output channel which can supply up to 50V at a current of 2A which equates to 100W maximum.

     

    Going back to the main page it clearly shows that the two outputs are connected together and shows the combined voltage and current setting for these channels as a whole. Very nice!

     

    4.2.4. Set Channel 2 and 3 to produce a single 24V rail with a 4A current limit.

     

     

    Much like we did above for connecting the two output channels in series, we can select parallel mode. In this mode the single resulting output channel is able to provide a maximum of 25V with a current of up to 4A which again equates to 100W maximum.

     

    If I press the button to choose 'Mode Parallel' you can see the display has updated to show how we now connect to the supply. In this case we connect across the Channel 2 outputs and leave the Channel 3 outputs unconnected as these supplies are connected together in parallel internally.

     

    Going back to the main screen we can see it has updated to show we are now in parallel mode.

     

    We can see that we have the 24V @ 0.5A originally set on Channel 2 but paralleled up with the same setting on Channel 3 to give us a total of 1A on the combines Channel 2 output.

     

    If we now go into the usual screen we can see that we can now set the current to 4A which is the combined maximum current of the two channels in parallel.

     

    Finally back to the main screen and we can see the resulting setting with the Channel 2 and Channel 3 outputs combined into a single output and a clear indication it is in parallel mode.

     

    4.3. The Web Interface

     

    The image to the left shows the main view of the web interface on the unit once you have browsed to the unit on the network and logged in. As you can see it is an almost exact clone of the main layout of the front panel of the physical unit. The buttons on the unit correspond exactly to clickable buttons on the web interface so the way you operate the web interface and the way you operate the physical unit are almost identical. The only slight difference is there are buttons labelled with arrows for turning the control knobs up and down rather than having a gesturing method to allow the knobs to be operated more naturally. This would be a benefit if using the web interface on a tablet as it would enable a more natural feel when using a touchscreen. But this is a minor niggle really in an otherwise very clear user interface.

     

    I would also like the option to be able to make the unit view full screen rather than it being only a part of a larger page. Again, if trying to use this interface from a tablet this would be a big advantage as currently it'll be a little more fiddly to use on the smaller screen with so much real estate taken up by non-critical information.

     

    At the bottom of the screen below the unit to the left is a screen capture button. The purpose of this is to grab and save a BMP image of the current screen of the unit, i.e. it's a grab of the contents of the LCD screen area only, not an image of the whole front of the unit. I really like this idea and will help with documenting tests much more easily. Unfortunately there is a small niggle with this which is that the screen capture doesn't appear to use any double buffering so it will quite happily grab a screen capture mid update so if you have a reading which is not stable you can get a capture with a mix of numbers before/after update which is quite frustrating. This should have been spotted and fixed early on, preferable before the unit was released as it's quite an obvious bug. None the less, it's still an excellent feature which I will use a lot, even if I do have to grab a couple of extra shots each time to get one that's not got any refresh related image errors.

     

    The other thing I would like to be able to do from this interface is specify a directory to download the captured screenshots as currently it just puts them into the browsers default download location. As well as this I would like to see them employing an image numbering system. With the current set up when I press the screen capture button the first time I get a file called screenshot.bmp. If I take another capture it creates a file called screenshot (1).bmp, then screenshot (2).bmp and so on. Maybe a better way would be to make the capture filename a combination of the unit's serial number and the current data/time such that even with multiple units available there would never be a conflict in the file names generated.

    4.4. BenchVue

     

    I had intended to take a look at how this supply integrates into KeySights BenchVue instrument control and automation suite. However, upon launching my Windows 10 virtual machine where I had previously installed an used the software I found it had disappeared which is totally weird. I then downloaded the installer for the latest BenchVue 2017 and tried to reinstall it and finally after about 4 hours it appeared to complete the installation, however upon looking for anything relating to BenchVue being installed I found almost nothing except for the BenchVue FieldFox app, none of the other apps and not the main application. Again, this was totally weird and disappointing. Fortunately I was able to resurrect a Windows 7 virtual machine from elsewhere and I found on this that BenchVue 2017 installed quite happily and comparatively quickly. Happy days!

     

    Unfortunately the happy feeling only lasted a short while. After loading the latest version of BenchVue I found that the majority of the modules for it are now only available at cost with the addition of Pro licenses. This is not a change I particularly like as the earlier version of BenchVue I had gave access to feature limited versions of the various modules so you could at least get a feel for its operation. I have this power supply, my oscilloscope and my multimeter, all of which are separate modules so the cost to buy these is significant. There is a trial version available for each of these but as I don't know how I might wish to use this yet I don't want to start the trial until such time as I am ready to invest some serious time into investigating and setting up BenchVue.

     

    4.4.1. External Links

     

    BenchVue Software 2017 Technical Overview: http://literature.cdn.keysight.com/litweb/pdf/5991-3850EN.pdf

    BenchVue Software 2017 Platform Website: https://www.keysight.com/main/software.jspx?ckey=2417463

     

    5. Lets Do Some Experiments!

    5.1. Powering-up the unit, how fast does it start?

     

    The first thing I noticed when I powered up the unit was that even though it's a smart power supply with a processor running a network stack and providing a web interface and various programmable options, as well as supporting a modern user interface with a large LCD, it powers up and is ready to use within just a few seconds. Below is a video showing the overall boot up speed of the unit.

     

     

    So as you can see, from me starting the camera recording, pressing the button to switch on the power supply to me stopping the recording, it's only 10 seconds in total, the power supply booting up is only a few of those seconds which is very nice. Nice one Keysight!

     

    5.2. Testing the Voltage and Current Capabilities

     

    5.2.1. Test Overview

     

    For this test I am going to use my DC electronic load which is a TTi LD300. This can support up to 80V input and up to 80A within a total power dissipation of 300W. For testing the outputs of the Keysight E36313A I will use the 80A constant current range to enable me to load Channel 1 of the power supply to 10A and I will use the 8A constant current range to load Channel 2 and Channel 3 of the power supply in their various independent, series, and parallel modes.

     

    The following tests are going to be performed on the Keysight E36313A only as we can assume that the TTi units perform to their load specs. I have used these for a number of years and I know they work as advertised in this respect.

     

    5.2.2. Set Channel 1 to 6V and Load with an Increasing Current up to 10A

     

    Keysight E36313A ConfigurationKeysight E36313A Results

     

    The voltage of the channel was set to 6V and the current limit was set to 10A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 10A.

     

    Condition
    Result
    6V, No LoadPass - Measured 6.003V on DMM
    6V, 1A LoadPass
    6V, 2A LoadPass
    6V, 5A LoadPass
    6V, 10A LoadPass - Measured 5.895V on DMM
    6V, Over LoadPass - Measured 1V on the DMM

    5.2.3. Set Channel 2 and Channel 3 to 25V and Load Each with an Increasing Current up to 2A

     

    Keysight E36313A ConfigurationKeysight E36313A Results

     

    The voltage of the channel was set to 25V and the current limit was set to 2A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 2A.

     

    Condition
    Result
    25V, No LoadPass - Measured 25.013V on DMM
    25V, 200mA LoadPass
    25V, 500mA LoadPass
    25V, 1A LoadPass
    25V, 2A LoadPass - Measured 24.994V on DMM
    25V, Over LoadPass - Measured 0.175V on the DMM

     

    The voltage of the channel was set to 25V and the current limit was set to 2A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 2A.

     

    Condition
    Result
    25V, No LoadPass - Measured 25.012V on DMM
    25V, 200mA LoadPass
    25V, 500mA LoadPass
    25V, 1A LoadPass
    25V, 2A LoadPass - Measured 24.994V on DMM
    25V, Over LoadPass - Measured 0.174V on the DMM

     

    5.2.4. Set Channels 2 and 3 into Serial Mode and to 50V and Load with an Increasing Load up to 2A

     

    Keysight E36313A ConfigurationKeysight E36313A Results

     

    Channels 2 and 3 were put into serial mode and the voltage of the combined channel was set to 50V and the current limit was set to 2A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 2A.

     

    Header 1Header 2
    50V, No LoadPass - Measured 50.01V on DMM
    50V, 200mA LoadPass
    50V, 500mA LoadPass
    50V, 1A LoadPass
    50V, 2A LoadPass - Measured 49.97 on DMM
    50V, Over LoadPass - Measured 24.7 on DMM

     

    5.2.5. Set Channels 2 and 3 into Parallel Mode and to 25V and Load with an Increasing Load up to 4A

     

    Keysight E36313A ConfigurationKeysight E36313A Results

     

    Channels 2 and 3 were put into parallel mode and the voltage of the combined channel was set to 25 and the current limit was set to 4A. Initially the output was unloaded and the voltage was measured using my Keysight U1272A Digital Multi Meter. The following table shows the results obtained from varying the load from 0A up to 4A.

     

    Header 1Header 2
    25V, No LoadPass - Measured 25.013V on DMM
    25V, 500mA LoadPass
    25V, 1A LoadPass
    25V, 2A LoadPass
    25V, 4A LoadPass - Measured 24.945V on DMM
    25V, Over LoadPass - Measured 0.379V on DMM

     

    5.2.6. Analysis of the Results

     

    Testing under various loads with the maximum voltages available on each channel and the Keysight E36313A didn't miss a beat. It works as expected and was very easy to reconfigure for each test.

     

    5.3. Looking at the regulation under load, light load and transient load conditions

     

    5.3.1. Test Overview

     

    This this test I am just going to compare the Channel 1 output of the Keysight E36313A with the TTi CPX400S and the Channel 2 output with Channel 1 of the TTi PL303QMD. I'll take a look at the ripple and stability of each of the outputs on my Keysight MSOX3054A Oscilloscope using an AC coupled voltage probe when loaded up the outputs with my TTi LD300 electronic load. I will used the web interface available with the LAN Option for the Oscilloscope to capture the resulting waveforms.

     

    5.3.2. Set Channel 1 of the Keysight E36313A and the CPX400S to 5V with a 10A Current Limit and Set the Load to 1A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi CPX400S Results  

     

    5.3.3. Set Channel 1 of the Keysight E36313A and the CPX400S to 5V with a 10A Current Limit and Set the Load to 10A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi CPX400S Results  

     

    5.3.4. Set Channel 1 of the Keysight E36313A and the CPX400S to 5V with a 10A Current Limit and Set a Step Load from 1A to 10A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi CPX400S Results  

     

    5.3.5. Set Channel 2 of the Keysight E36313A and Channel 1 of the PL303QMD to 25V with a 2A Current Limit and Set the Load to 200mA.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi PL303QMD Results

     

    5.3.6. Set Channel 2 of the Keysight E36313A and Channel 1 of the PL303QMD to 25V with a 2A Current Limit and Set the Load to 2A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi PL303QMD Results

     

    5.3.7. Set Channel 2 of the Keysight E36313A and Channel 1 of the PL303QMD to 15V with a 2A Current Limit and Set a Step Load from 200mA to 2A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi PL303QMD Results

     

    5.3.8. Analysis of the Results

     

    We can see from the results that all three supplies are very good. The Keysight E36313A has strong performance in all the tests, beating the TTi CPX400S in the transient load and output noise measurements, where the TTi CPX400S had some noticeable regular switching spikes which increased with current. At the higher voltage and lower current tests the Keysight E36313A performed roughly on a par with the TTi PL303QMD, having slightly more excursion low but slightly less excursion high on the transient voltage test.

     

    Under 200ma/2A transient load test the TTi power supply would run but would occasionally trip even though I had actually set the current limit to a little over 2A. They Keysight E36313A did not trip out during this test at all.

     

    5.4. FFT analysis of the fully loaded output

     

    5.4.1. Test Overview

     

    For this test I will look at just the single output with 1A and 10A load conditions setup from the previous tests and using the FFT function of my Keysight MSOX3054A I will attempt to see if there are any noticeable peaks in the spectrum which are dependant on load which are detectable within the capabilities of my oscilloscope. I will used the web interface available with the LAN Option for the Oscilloscope to capture the resulting waveforms.

     

    5.4.2. Set Channel 1 of the Keysight E36313A and the CPX400S to 5V with a 10A Current Limit and Set the Load to 1A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi CPX400S Results  

     

    5.4.3. Set Channel 1 of the Keysight E36313A and the CPX400S to 5V with a 10A Current Limit and Set the Load to 10A.

     

    Keysight E36313A ConfigurationKeysight E36313A ResultsTTi CPX400S Results  

     

    5.4.4. Analysis of the Results

     

    Looking at the results we can see that the TTi CPX400S has got a higher peak at 125MHz and additional spurs at 187.5MHz, 200MHz, 212.5MHz and 225MHz which are either not present or at a much lower level on the output of the Keysight E36313A. These likely correlate with the edge speed of the switching noise we saw in the previous output noise tests but without further investigation I cannot be sure.

     

    We can also see from the FFT that there are spurs in the 85MHz to 105MHz range for all tests and all equipment. These are present even under no load and with the output disabled on both units, I think these are actually artefacts which are caused by some digital data being picked up from elsewhere. I haven't tracked down from exactly where yet but if we look at the following images you can see the regularity of the bursts and with the zoomed image we can see something which looks like it might be in the 20MHz-25MHz range. It's obviously very hard to see the details of the data streams from a spurious waveform captured on my oscilloscope.

     

     

    5.5. Testing out the data logging

    5.5.1. Test Overview

     

    For this test I will be capturing a set of data over time and recording it to a file which I will then import into a spreadsheet application to perform some graphing of the results. I have chosen to log the Voltage, Current and Power measurements when booting up a Raspberry Pi Model B and running some benchmark tests. For my tests I will be performing 5 separate actions

     

    1. Booting up the Raspberry Pi from powered off and logging in.

    2. Running a sysbench benchmark on the CPU to calculate prime numbers.

      sysbench --test=cpu --cpu-max-prime=2000 run
    3. Running a sysbench benchmark on the Memory to write 2GB of data.

      sysbench --test=memory run --memory-total-size=2G
    4. Running a sysbench benchmark on the Memory to read 2GB of data.

      sysbench --test=memory run --memory-total-size=2G --memory-oper=read
    5. Shutting down and powering off the Raspberry Pi.

      sudo shutdown -HP now

     

    5.5.2. Performing the Tests

     

    The unit comes with a relatively straight forward to use data logger. You can configure what values are captured, i.e. V/I/P from Channels 1/2/3, you can configure how long it captures for, how often it samples the data etc. As it's logging it will show you the waveform of the log in a graph which is like a little oscilloscope with a slow time base. You need a USB stick to capture the data and you can save it in a binary dlog format and also in CSV format.

     

    5.5.3. Test Data Collected

     

    The following image shows the log view of the data collected:

     

    I also captured the log data into a CSV file:

     

    E36313A exported datalog
    File type: CSV
    
    
    "Sample interval: 0.200000"
    "Number of sample: 1026/1650"
    "Trigger sample: 0"
    "Date: 2017/12/19 14:28:28"
    
    
    "V1: 5.000000, -7.500000"
    "I1: 0.200000, 0.150000"
    "P1: 1.000000, 2.781250"
    "V2: 5.000000, 0.000000"
    "I2: 1.000000, 0.000000"
    "P2: 2.000000, 0.000000"
    "V3: 5.000000, 0.000000"
    "I3: 1.000000, 0.000000"
    "P3: 2.000000, 0.000000"
    
    
    Sample,"Volt avg 1","Curr avg 1"
    0,0.001310,0.000070
    1,0.001310,0.000070
    2,0.001310,0.000070
    3,0.001310,0.000070
    4,0.001310,0.000070
    5,0.001310,0.000070
    6,0.001310,0.000070
    7,0.001310,0.000070
    8,4.999190,0.084240
    9,5.000390,0.113180
    10,5.000590,0.095300
    11,5.000590,0.076760
    12,5.000590,0.102770
    13,5.000590,0.098550
    14,5.000590,0.067660
    15,5.000590,0.098220
    16,5.000590,0.104070
    17,5.000590,0.107650
    18,5.000590,0.082940
    19,5.000790,0.067330
    20,5.000590,0.067330
    21,5.000590,0.067330
    22,5.000590,0.067330
    23,5.000590,0.074490
    24,5.000590,0.127810
    25,5.000590,0.127810
    26,5.000590,0.128130
    27,5.000590,0.121630
    28,5.000590,0.141140
    29,5.000590,0.111550
    30,5.000590,0.149920
    31,5.000590,0.156750
    32,5.000590,0.157070
    33,5.000590,0.115780
    34,5.000590,0.115780
    35,5.000590,0.115780
    36,5.000590,0.115780
    37,5.000590,0.187960
    38,5.000590,0.227950
    39,5.000790,0.194140
    40,5.000590,0.242910
    41,5.000590,0.259490
    42,5.000590,0.281270
    43,5.000590,0.288100
    44,5.000590,0.277040
    45,5.000590,0.278350
    46,5.000590,0.277690
    47,5.000590,0.278020
    48,5.000590,0.262410
    49,5.000590,0.323210
    50,5.000590,0.279970
    51,5.000590,0.280950
    52,5.000790,0.307280
    53,5.000790,0.280950
    54,5.000590,0.269570
    55,5.000790,0.271190
    56,5.000590,0.270220
    57,5.000790,0.255590
    58,5.000590,0.260460
    59,5.000590,0.267940
    60,5.000790,0.280620
    61,5.000790,0.250060
    62,5.000790,0.264690
    63,5.000590,0.261110
    64,5.000590,0.251360
    65,5.000590,0.251360
    66,5.000590,0.251030
    67,5.000790,0.258190
    68,5.000790,0.249730
    69,5.000590,0.262740
    70,5.000590,0.261440
    71,5.000790,0.253640
    72,5.000590,0.259810
    73,5.000590,0.278350
    74,5.000790,0.240300
    75,5.000590,0.251030
    76,5.000790,0.266640
    77,5.000590,0.253960
    78,5.000590,0.258190
    79,5.000590,0.254940
    80,5.000790,0.267290
    81,5.000590,0.251030
    82,5.000590,0.259160
    83,5.000590,0.246810
    84,5.000590,0.262090
    85,5.000590,0.252330
    86,5.000790,0.257210
    87,5.000790,0.252010
    88,5.000790,0.251360
    89,5.000790,0.253640
    90,5.000590,0.254940
    91,5.000590,0.245830
    92,5.000590,0.235430
    93,5.000590,0.234780
    94,5.000790,0.235430
    95,5.000590,0.237380
    96,5.000590,0.271520
    97,5.000590,0.247130
    98,5.000590,0.235430
    99,5.000590,0.235430
    100,5.000790,0.252010
    101,5.000590,0.236730
    102,5.000790,0.250060
    103,5.000790,0.252010
    104,5.000790,0.260790
    105,5.000790,0.250060
    106,5.000590,0.254610
    107,5.000590,0.256890
    108,5.000590,0.278020
    109,5.000790,0.257210
    110,5.000590,0.245830
    111,5.000790,0.258840
    112,5.000590,0.250380
    113,5.000590,0.252010
    114,5.000590,0.238030
    115,5.000590,0.249730
    116,5.000590,0.254940
    117,5.000790,0.239980
    118,5.000590,0.252980
    119,5.000790,0.250380
    120,5.000590,0.236400
    121,5.000590,0.251030
    122,5.000790,0.268920
    123,5.000590,0.250380
    124,5.000590,0.259490
    125,5.000790,0.261440
    126,5.000590,0.252660
    127,5.000590,0.242580
    128,5.000590,0.252980
    129,5.000590,0.254940
    130,5.000590,0.258190
    131,5.000590,0.260790
    132,5.000590,0.257210
    133,5.000790,0.240950
    134,5.000790,0.235100
    135,5.000590,0.250380
    136,5.000590,0.240630
    137,5.000590,0.251360
    138,5.000590,0.253960
    139,5.000590,0.260460
    140,5.000790,0.251680
    141,5.000790,0.250710
    142,5.000590,0.241280
    143,5.000590,0.272170
    144,5.000590,0.235430
    145,5.000790,0.235100
    146,5.000590,0.235430
    147,5.000590,0.237050
    148,5.000590,0.240300
    149,5.000590,0.235100
    150,5.000590,0.248110
    151,5.000590,0.248760
    152,5.000590,0.235100
    153,5.000790,0.248430
    154,5.000590,0.268590
    155,5.000590,0.269570
    156,5.000790,0.227950
    157,5.000590,0.211040
    158,5.000790,0.210720
    159,5.000590,0.210720
    160,5.000590,0.210720
    161,5.000590,0.210720
    162,5.000590,0.210720
    163,5.000590,0.210720
    164,5.000590,0.210720
    165,5.000590,0.211040
    166,5.000590,0.210720
    167,5.000590,0.211040
    168,5.000590,0.210720
    169,5.000590,0.210720
    170,5.000590,0.210390
    171,5.000590,0.210720
    172,5.000590,0.210390
    173,5.000590,0.210720
    174,5.000590,0.211040
    175,5.000590,0.210720
    176,5.000590,0.210720
    177,5.000590,0.211040
    178,5.000590,0.210720
    179,5.000790,0.210720
    180,5.000790,0.210390
    181,5.000590,0.210390
    182,5.000590,0.210720
    183,5.000590,0.210720
    184,5.000590,0.210720
    185,5.000590,0.211040
    186,5.000590,0.211370
    187,5.000590,0.210720
    188,5.000590,0.211370
    189,5.000590,0.210720
    190,5.000590,0.210390
    191,5.000590,0.280620
    192,5.000590,0.279970
    193,5.000590,0.279650
    194,5.000590,0.281270
    195,5.000590,0.280620
    196,5.000590,0.279320
    197,5.000590,0.280620
    198,5.000590,0.279000
    199,5.000590,0.279000
    200,5.000590,0.225020
    201,5.000590,0.210390
    202,5.000590,0.211040
    203,5.000790,0.210720
    204,5.000590,0.210720
    205,5.000590,0.210720
    206,5.000590,0.211040
    207,5.000590,0.210720
    208,5.000590,0.210390
    209,5.000590,0.210720
    210,5.000590,0.210720
    211,5.000590,0.210720
    212,5.000590,0.211040
    213,5.000590,0.210720
    214,5.000590,0.210720
    215,5.000590,0.210720
    216,5.000590,0.210720
    217,5.000590,0.210720
    218,5.000590,0.210720
    219,5.000590,0.210720
    220,5.000590,0.210720
    221,5.000590,0.210720
    222,5.000590,0.211040
    223,5.000590,0.211040
    224,5.000590,0.210720
    225,5.000590,0.211040
    226,5.000590,0.210720
    227,5.000590,0.210390
    228,5.000590,0.210720
    229,5.000790,0.210720
    230,5.000790,0.210720
    231,5.000790,0.210720
    232,5.000790,0.210720
    233,5.000790,0.210720
    234,5.000790,0.210720
    235,5.000790,0.210720
    236,5.000790,0.210720
    237,5.000590,0.210720
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    1025,5.000590,0.071560

     

    For some reason it has not included the logged power data in the CSV file. I need to investigate why this is the case. It's not actually an issue as we can reconstruct the power from the V and I data, which I will do in excel with a simple formula.

     

    5.5.4. Using the Results Data

     

    Once you have the data in a useful format there are many things you could so with it depending upon what the data represents. The simplest thing you can do is simply graph the data in Excel or Open/LibreOffice Calc (other Spreadsheets are available too, just use whatever you like and/or are familiar with). The following is a graph of the current (blue trace) and calculated power (red trace) for the experiment of booting up the Pi and running various benchmarks.

     

    Using such tools you could easily calculate the average power consumption of a piece of equipment over time, or correlate particular operations happening on the hardware or in the software with peaks in power consumption, which,  if you are designing something that is required to run on batteries and needs to be low power, this can give some real insights into where to target your efforts in the design to get the best performance for the lowest power consumption.

     

    You could of course bring the data into more comprehensive tools like MatLab, Octave, etc or write your own custom tools to process the data specific for your needs.

     

    UPDATE 21/12/2017:

     

    I've been experimenting and using the logging a little more and it really is very useful and as dougw shows in one of the videos in his road test, there are plenty of more creative ways to make use of the logger. I have found a few limitations though which I think could be improved upon.

     

    Firstly, when you set the logging period for an extended time, it gets to a point where is says there is not enough device memory and it starts to increase the logging interval. Why is this? If I am logging to a say 16Gb USB stick why am I restricted to the log size based upon memory available within the power supply itself? I would have thought even if it needs to use internal memory to capture the initial data, flushing this data to a file periodically should allow this to be able to continuously log until the USB is full. I hope this is something that can be corrected to allow the logging to be used more effectively for long term experiments.

     

    Secondly, in order to start the logger I have to have a USB stick installed. What if I don't have a USB stick available? The logger then becomes unusable. This is a network connected device so why not have the ability to save to a network location or even use some remote logging server which the unit can connect to easily to store the logs?

     

    Finally, I have noticed some waveform glitches on the display, regularly part of a trace will disappear for a second and then reappear. It's quite distracting having a flashing trace on the log view.

     

    As a quick follow up to the earlier comment about the power trace not making it into the CSV file, I have not discovered the reason for this yet. If it's there as a trace I can enable for logging it should be in the file. Yes, I can create it from the V and I for the trace but if I have a long data set adding that column to my spreadsheet is fiddly and involves lots of scrolling. This should also be fixed. While I still think the logging is a great feature and very welcome, it isn't bug free and does have some limitations so for now I'm going to amend my review score down a point for the bugs and the newly discovered logging limitations. If a new firmware is released that resolves these issues I will report back and amend the score accordingly.

     

    5.6. Using the Rear Outputs for 4-Wire Connections

    5.6.1. Why 4-Wire Connections?

     

    In an ideal world your wires which connect your power supply to your load would have zero or negligible impedance, but in reality there is a small impedance present, usually in the order of a few tens or hundreds of mOhm for typical bench hook up cables. For low current applications this small impedance makes almost no difference and the voltage measured directly at the load is almost identical to the voltage measured at the output of the power supply. As the current increases, using Ohms law (V = I/R) we can soon see how higher currents could lead to a significant drop in the voltage between the source and the load. In order to compensate, if the load was constant you could just raise the source voltage until the load voltage was at the desired level, but this is not a suitable approach as the load could change and you may end up with an over-voltage condition on the input to your load.

     

    Usually the power supply will feed back the voltage it is using to control the output of the supply from as close to the output as possible. This compensates for any losses in the output stage of the supply but does nothing to help the case where there are additional external losses. This is where 4-Wire connections come into play. An additional pair of wires connect from the power supply to the load and these are used as dedicated sense pairs to measure the voltage directly at the load. These sense wires carry none of the output current so there is no current related voltage drop, it's an accurate measurement of the voltage directly at the load. This measurement is used instead (or as well as) of the internal voltage measurement to enable to supply to automatically deliver the desired voltage directly at the load.

     

    5.6.2. The 4-Wire Test Setup and Results

     

    Keysight E36313A ConfigurationKeysight E36313A Results

     

    With the output set to 2-Wire mode with a 5V output and 6.66A load (as reported on the TTi LD300 DC Electronic Load) the voltage measured on my DMM is 4.428V. This means that in my cabling between the power supply output and the load there is almost over 0.57V dropped. This is plenty to cause issues for test devices which require 5V +/-10%.

     

    Update 20/12/2017: Having thoroughly investigated my strange readings I have discovered there was an issue with the measurements on my DMM and the voltages I was reading were not correct. Switching my TTi LD300 into meter display so it shows the voltage it sees on it's input and the current it is sinking, with a 10A load and in 2-Wire mode, the voltage at the input to the load is just 4.05V. If I vary the load the measured voltage varies as expected.

     

    So it turns out the optimal test current for my particular the 4-Wire setup to be able to correct back up to exactly 5.000V as measure on my DMM is 6.66A. Above this and the PSU doesn't have enough headroom to be able to recover the voltage drop. But up to this, in my setup and the supply perfectly corrected back to exactly 5.000V.

     

    Now to a slight issue, I then dropped the load to only 1A and the supply now incorrectly gives 5.168V measured on my DMM at the load. I need to do some more investigation on this as this is clearly not correct. I need to double check all my test setup and do some more analysis and see if I can fathom what is happening here.

     

    Update 20/12/2017: As stated above, the readings from my DMM were incorrect. On the TTi LD300 meter view, with a 10A load and 4-Wire connections enabled the reading is now exactly 5.00V. This measurement now remains constant regardless of the load.

     

    6. Road Test Summary and Conclusions

     

    All in all I think this unit is very good. It packs in a lot of features and provides a really nice to use interface to access the features. My unit came with the USB/LAN and GPIB interfaces to connect with other systems easily and this opens up a whole lot of additional possibilities. I initially knocked off a couple of points in the "Performed to Expectations" section, one because of the mains hum from my unit, and one for the little niggles I discovered in the UI. Keysight will hopefully provide a firmware update to fix the UI issues at some point. With their response regarding the hum issue and their prompt action to replace my unit I am adding back the point I deducted for this as it appears to be specific to my unit and they are in the process of resolving the issue for me.

     

    In comparison to the TTi units I already have you can see that it performs well. To be fair to TTi, all three unit's are very good but I think the Keysight E36313A out performs the TTi units in a few areas and the user interface and feature set is a deciding factor for me. The output can be seen from the various load tests and FFT's to be a little cleaner and some higher frequency artefacts which are present on the output of the TTi supplies are either not present or much reduced on the Keysight E363213A in comparison.

     

    One thing I can't do with my TTi supplies is easily log data and this is a very valuable tool which the Keysight E36313A makes really easy to use. I can easily log the Voltage, Current, and Power from each of the three channels and then use this data to present these values in a useful and meaningful way or to process the data to extract hidden information such as tracking the overall power consumption of a low power device with many different power states over time.

     

    This concludes my Road Test Review of the Keysight E36313A. Thank you all for reading this review and thanks again to Element 14 and Keysight for choosing me for this Road Test. It has been an honour to receive this item and a pleasure to go through and do a comprehensive review of this excellent piece of equipment. It's now 100% my go to power supply in my lab.

     

    20/12/2017: I've updated the section above regarding the 4-Wire connections to correct my test results and report that is it in fact working well and exactly as expected.

    21/12/2017: I've updated the section above regarding the logging capabilities to add my additional findings and limitations.


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