First of all I would like to thank Element14 Keysight and Texas Instrument for the big opportunity to test these extraordinary pieces of equipment It's long time since the package for the roadtest arrived down my home and since then I have had the opportunity to use and judge the Keysight multimeter and make some experiments with the Texas Instrument DAC8734 Evaluation Module This is my first roadtest and I have to say It's not as easy as I thought
Only now I'm publishing this article I wrote long time ago, when I received the multimeter and the evaluation board, for this reason you will not find any impression of a person used to these instruments.
Let's start from the beginning!
It took a long time to get the package. Since the day that the roadtest winners' names were published I had the doubt it had ended before it had began, but in the end all went good and thanks to Dave of Element14 I received the items for my review/experimentation.
When the box arrived I was so excited that I had time to take only few photos and then I unpacked without making any video as promised... When the carrier arrived I was a bit worried because the box was marked “Keysight” and I thought the TI EVM was missing, but when I opened the box it was there, in a small antistatic bag.
I was surprised to see only the instrument box to protect this expensive gear that had travelled across the ocean, I don't know if just this box is enough to protect or if this is a common way to ship, even though everything was delivered and fortunately all worked!
My first attention was on the wonderful Keisigth multimenter I forgot the TI evaluation board for a bit Beyond the Keisight in my package there was
- Calibration Certificate dated 28 July (the same as my birthday )
- A flyer that explains that Agilent has become Keysight Tecnologies
- A set of probes and accessories that I will illustrate further
- A classic white USB A to B cable
- An American power cord
So my first problem was to find a power cord, because the shipped one didn't fit in my outlet; and naturally when you need something it is common to lay around and never find it!
WARNING: before plugging your instrument you must select the right line voltage for your country, in my case 220V. If you don't do so you could damage irreparably your instrument!
After some struggle I powered the instrument! It took a bit of time to start up and show the user interface, every time you power the multimeter on it will take some time (I measured about 30 seconds) for software loading and configuration, hardware initialization and verification and at the end some relay clicking probably to make some auto-calibration/adjustment. Even if you shut it down with the front panel power button it will take the same time to power on. The cooling fan is relatively quiet; when it's on in a silent room a slow rustle can be heard, but I'm sure that it want be noticed in a laboratory environment.
The power button it's a soft one and there isn't any power switch on the back. If you unplug the instrument when it's on and you plug it on again it will switch on automatically, there isn't any menu configuration (or at least I'm not able to find it) to enable or disable the power-on state.
From the menu you can add an optional power on message to be displayed, a useful option if you have more than one! On the frontal panel there is a LED that's ever on: when the instrument is on it's green, when the multimeter is off it's orange.
My first impression was really good but what would you expect from such a high class instrument?
A big display and many rubber buttons on the right and under its. From the frontal panel you can quickly choose the measurement you are interested in. The blue shift button adds more functions to the existing buttons, not a new feature. The difference among the buttons is intuitive: white for measure function, blue for soft buttons and gray for settings. The buttons are not back illuminated, this could be a problem in dark laboratories, it would be a good choice to produce at least illuminated bush buttons.
In my point of view a useful missing button is an Exit button that permits to go back to the main acquisition window when you are in functions or settings; besides there are dangerous functions as the second function “Reset” on the “Run/Stop” button, even if it asks you for confirmation before you reset why does it have it as a second function and not in the “Utility” menu? Who needs a quick access factory reset?!
It was a good idea to put the current measurements over the corresponding voltage measurement, this choice facilitates, in my opinion, the search of these functions.
The color display is very clean, the color scheme is pleasant to see. A black background highlights the blue tabs with the yellow measure digits. At first glance the most impressing and exciting thing is the number of digits you see on the display: 7 and ½; I have never seen so many digits on a multimeter. The gray/bluish color of the bottom menu makes a good separation from the measure window. In addition the color scheme is appropriate and smart: yellow for the main words, which have to catch your attention; white for the setting names and light gray for the unselected options.
On the contrary the menu is unsatisfactory, for example in the DC voltage measurement and others. The Aperture setting has a top sub menu to select the number of PLC or the aperture time while a new menu appears when you press the range button. To make your selection you must use the soft buttons under the display besides arrow buttons like in the first case, but for the range selection there is a dedicated set of 3 buttons right of the arrow buttons.
Now let's return to the TI evaluation board It arrived in an antistatic bag without any kind of box and accompanied only by a small flier that send you on the ti.com site The board itself is really small and has many jumpers and test-points really useful when you are making tests When I applied for this roadtest I looked at the amazing characteristics of that board that come from 3 main devices DAC8734 REF5050 and REF5050 The first is a high-accuracy digital to analog converter(DAC it has 4 16bits channels the last two are references voltages ICs respectively 5V and 2.5V both low noise low drift high accuracy devices
The board has plenty of connectors on both sides, it has been made to connect with other identical evaluation modules or of the same family but this isn't my case.
Before starting any kind of experiment it is a good idea to take a careful reading of the data sheets and user manual. Even tough the board documentation is straightforward to find on ti.com, in my own opinion it's not clear and misleading; the only thing to do is go to the last page of the user manual and print the schematic, that's probably better than the rest of documentation.
To enable the board you need at least some power sources:
- +5V: used to power the digital section of the DAC8734 IC
- +VA/-VA: used to power the analog section of the DAC. The +VA is used even to power even a local linear regulator (TL751L08) that powers the reference ICs (REF5050 and REF5025). For these power rails is specified a supply of at least 4.75V but to make work correctly you will need a voltage greater than 8.5-8.6V to make the local LDO work.
If you look carefully the schematic you can see that there's a plenty of decoupling capacitors near, so as first test I decided to use a linear bench power supply to power everything without any additional board. Even a better choice could be to use a small board with standard old fashion linear regulators or a new one with switching power supply. I decided to power the board with +-12V, the onboard LDO will provide enough PSRR to have a clean and stable supply for the references.
This board isn't really made to be used as a standalone reference voltage, or to test the reference ics but using the two test points TP1 and TP2 and setting the two switch one on 2.5V and the other on 5V you could test the performances of these ics.
Texas Instrument's engineers clearly kept the board as simple as possible, with only few necessary components, they made it in a way that no one has to struggle to understand how it works. The schematic is available at the end of the user guide but there is no layout available! The board is more than 2 layers, probably 4, and looking in backlight there's a separation between digital and analog ground, it would be interesting to see TI's engineers layout techniques. Even more, I would have liked to see other onboard linear regulators for the positive and negative power rails for the analog portion of the DAC, because to achieve high performance you should try to minimize any kind of external noise that can be picked up with long cables and tracks, but probably the board is not meant to be an high precision instrument as I see it.
As I proposed in my roadtest application, next time I will show some experiments involving the multimeter and the evaluation board; I'll try to explain the meaning and the differences between accuracy and resolution.
As a bonus I would like to add some links to the online documentation:
- Keysight product page 34470A Digital Multimeter, 7½ Digit, Performance Truevolt DMM | Keysight (Agilent)
- Keysight product Data Sheet http://literature.cdn.keysight.com/litweb/pdf/5991-1983EN.pdf?id=2318052
- Texas Instruments product page DAC8734 Evaluation Module - DAC8734EVM - TI Tool Folder
- Texas Instruments User Guide DAC8734EVM User Guide (Rev. B)
- Texas Instruments DAC8734 Data Sheet: Quad, 16-Bit, High-Accuracy, ±16V Output, Serial Input D/A Converter (Rev. A)
- Texas Instruments REF5025/5050 Data Sheet: REF50xx Low-Noise, Very Low Drift, Precision Voltage Reference (Rev. G)
I hope my review will be of your interest; any comment is appreciated.