Note If you find this  U1282AU1282A multimeter related post of interest then other similar topic ones in the series are here

Keysight U1282A Data Logger Software

U1282A Test Bed Integration, Equations and Testing the Raspberry Pi 3

Raspberry Pi 3 Dynamic Current Consumption, Power and Temperature Tests

 

Introduction

The U1282AU1282A is a precision multimeter but also rugged – it looked perfect for automotive applications and I wanted to apply it towards getting to know the car battery better!

Ordinarily some vendors offer oscilloscopes for automotive use, but I was curious to find out if the 10Hz logging rate that the  U1282AU1282A supports could be useful as a lower cost alternative for some tests.

In addition, the  U1282AU1282A has some features clearly intended for industrial applications so I wanted to investigate those too.

 

Bluetooth Connectivity

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It is not always easy to have a PC nearby, so to make things convenient there are a couple of IR-to-Bluetooth adapters available for the  U1282A.U1282A. One has a 10m range and the other has a 100m range. The 10m range Bluetooth adapter10m range Bluetooth adapter is very low cost, and so could be an easy decision to automatically add to the purchase if you’re buying the multimeter. In the end I went with the 100m range Bluetooth adapter100m range Bluetooth adapter; I may never need such a range but the multimeter will give many years of service and I cannot predict future needs.

If you also have earlier U1200 series devices then the same IR-to-Bluetooth adapters are compatible with them too. The U1240 series multimeters do need a U1179A bracketU1179A bracket though.

 

The IR-to-Bluetooth unit is well constructed but not rubberized. If the multimeter and IR-to-Bluetooth adapter were to fall off the desk possibly they might disconnect but I doubt any damage would occur. Besides the  U1177AU1177A is quite low cost and wouldn’t be too painful to self-fix or replace or have repaired. It comes with two AAA batteries and these are expected to provide power for 20 hours before they need replacing.

 

The unit can be used with the same software that is used with the IR-to-USB cable that comes with the  U1282A,U1282A, and there is free mobile software too(search for Keysight Meter Logger in the Android or Apple app stores.

 

The PC and mobile software is similar but the feature set isn’t entirely the same. The mobile version is missing high speed logging (it instead logs once per second) but benefits from a ‘math mode’ which the PC software doesn’t have (described later).

 

To cut a long story short, I was deeply impressed with the mobile software. Functionality-wise it does everything I would need it to do. It looks after logs captured, and I can view them again at any time using the software, and can immediately export to CSV or PDF format or obtain images and save them or share them via e-mail, Twitter or whatever. Basically complete integration with other mobile apps through the sharing capability that exists in Android.

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Performance-wise I’d love to see the high speed logging capability appear. The  U1282AU1282A series is new though so it is probably on their feature-request list(I’ve asked Keysight, will update here when I find out). The other small changes I’d like to see are related to the Math Mode. This is a neat yet simple feature to allow arbitrary equations to be executed on the captured data and then plotted to the screen. It is extremely powerful. For maximum usability I’d like to see exponentials (today I have to type 0.000001 for example rather than represent it as an exponential) and an ability to store equations within the software (the workaround is to copy-and-paste to a notepad inside your mobile device); It is not too big of a deal. More on equations later, but first I wanted to do something simple: check the car battery voltage during starts!

 

Car Battery Measurements

My car battery is in the rear boot (trunk). It was easy to clip directly onto the car battery and leave the multimeter placed in the boot, close it and then sit in the driver seat to conduct the tests! Bluetooth is great (incidentally these croc clipsthese croc clips are also great. I use them for electronics work (they can grip thin wire strands) but they also easily fit around car battery clip screw threads).

 

Don’t forget to set the range to 600V (so that it doesn’t auto-range during the test).

 

The car battery is a Bosch one, from Halfords, but I’ve had the same model previously from Halfords too and it failed within a couple of years. I have had this battery for about a year and it is not particularly healthy.

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By running the Meter Logger software on the tablet, I had two free hands to start up the car as usual and observe what was going on with the battery voltage. This test verified the car battery voltage with the engine switched off, the voltage during engine startup and the voltage while the alternator was running. I could not have done this easily without the multimeter – I do not have a portable oscilloscope, nor would I have wanted to carry a full-size oscilloscope out to the car, power it from mains and then set up a suitable trigger just to run a quick battery test.

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Now that I have the information captured I can quickly save the screen capture to my mobile phone all ready to compare it when I rerun the test during the winter. So simple! I love that I can use this multimeter for such vehicle applications It will not replace an oscilloscope and of course will miss all high speed signals but as mentioned, realistically I would not have used an oscilloscope in the vehicle unless I really needed to. The  U1282AU1282A and a cheap OBDII device are my two main vehicle diagnostic tools now. I’ll be even happier when the 10 captures per second capability can be introduced to the mobile app.

 

Frequency Measurement and Square Wave/PWM Generation

The frequency measurement capability on the  U1282AU1282A is extremely handy. I have yet to measure its limits but I’ve noticed that it can handle far lower level signals than the Fluke 175. It was trivial to hook up a phototransistor (it has a signal of the order of a few hundred mV) directly to the meter and then observe the mains frequency by pointing it at a neon lamp. In industrial applications where a voltage has been converted to a frequency the meter and equation capability can report it back as a usable value.

 

The  U1282AU1282A also has a signal output function: it can generate square waves and PWM. This capability would be very handy to simulate certain sensors (e.g rotary speed sensors, turbine type flow meters) in an industrial environment. With a couple of  U1282AU1282A multimeters you could perform an end-to-end test having one  U1282AU1282A simulating this type of sensor, and the other  U1282AU1282A measuring the voltage or current output from the conditioning/converter device and automatically applying an equation using the Meter Logger software. Although there are dedicated tools for such scenarios, it is great that a couple of multimeters can also solve such problems.

 

The  U1282AU1282A won’t replace a signal generator for a number of reasons, in particular that it can only generate certain frequencies between 0.5Hz and 4.8kHz (total of 29 frequencies but the duty cycle is very granular(0.39 to 99.609 in 256 steps for all frequencies) and yes you can hold down the button to race through them. The output is fixed at 2.2V peak-to-peak so as well as for sensor simulation, it is also fine for 3.3V logic and some 5V logic family interfacing too. The frequency accuracy for output signals (it is rated as ‘typical' by the way so it shouldn’t be expected to act as a lab reference) but nevertheless the output frequency accuracy is very good! I was surprised It is enough for field process calibration use most likely. As a test it was set to 50Hz and it measured 49.9985Hz on an uncalibrated meter. The same uncalibrated meter reported 49.9998Hz from another frequency reference. The pulse width duty cycle performance is not bad either (typical max error is 1/256 of the period). In conclusion the  U1282AU1282A isn’t merely doing lip service by adding features; the features are well executed.

 

Working with Sensors

The value of equations for the U1282A has been discussed earlier (for an example of it in action see the video below - it was used to dynamically measure heatsink temperature for the Raspberry Pi 3 during stress tests).

 

By providing equation capability in its mobile software, the  U1282AU1282A can be used in scenarios that were never generally considered for multimeters. In the past dedicated devices or offline data loggers would be needed for measuring things like temperature, flow rate, pressure, speed in RPM, light level and so on. With the  U1282AU1282A exists the capability to measure many things provided we have a sensor for it. In industrial applications the output from a sensor can be a voltage in the range of 0 to 10V or a current up to 20mA. Both of course can be measured with any multimeter or a process indicator/display. However the conversion to a real-world parameter isn’t always easy. And with a normal multimeter while 0 to 10V could be mentally translated into a 0 to 100 value it isn’t as easy with a 20mA output type device especially if the range is 4.20mA. With the  U1282AU1282A the equations come in extremely handy and solve all these problems.

 

Example Applications

Temperature

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The handy Betatherm thermistorBetatherm thermistor can provide an easy temperature measurement, provided the following formula is entered into the Meter Logger software. The non-linear resistance to temperature relationship of the thermistor is taken care of in the formula. Set the meter to Ohms, apply the formula and the entire system provides a very accurate temperature measurement solution.

 

(1/7(0.0007987407898+(0.0002125901507*ln(MA))+((0.00000007077938365)*(ln(MA)^3))))-273.15

 

 

Linear Travel

As another example, if a machine needed aligning it could be easier to have a measurement in millimetres rather than a voltage from a sensor. If the machine had a linear potentiometerlinear potentiometer fitted, then this is not a problem!

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Magnetic Flux Density

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A magnetic flux density (Gauss or Tesla)-meter was constructed using a hall sensor device, and by plugging in the relevant formula it was possible to see that it was performing as expected (incidentally, the Analog Devices AD22151 appears to be fairly accurate from what I can tell.

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It was refined by accurately measuring each component in the circuit using the multimeter and adjusting the equation accordingly. I didn’t have an easy way to confirm, but I got Gauss values very close to the expected ballpark when using a small magnet placed on top of the industry standard 9.6mm (well, Lego Industry standard i.e. a Lego brick height). There is an excellent magnet calculator here.

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Summary

The IR-to-Bluetooth adapter from Keysight is really worthwhile for extending the scenarios that the multimeter can be used for. Keysight’s Meter Logger Software for mobile devices worked well and did almost everything I could have wanted. Nothing is perfect and a mini feature request list has been submitted to Keysight (any update will be posted here when available). No issues were observed that couldn’t be worked around.

 

The  U1282AU1282A can be useful in automotive tests, where the 10Hz rate can be a useful in-between sampling rate between a normal multimeter and an automotive oscilloscope.

 

For industrial scenarios, the Bluetooth adapter and the Math Mode (equation feature) means that real time measurements can be taken in the units that make sense, regardless of the attribute being measured. The frequency measurement and generation capabilities are well executed and will come in extremely handy for calibrating sensors, or for simulating them. A couple of  U1282AU1282A devices would be handy for industrial scenarios, where they can perform some functions that some industrial calibration devices cannot, such as the frequency measurement. A pair of them can be used for any measurement function totally isolated from the frequency generation function for end-to-end tests.

 

Some example scenarios were covered such as car battery monitoring, safe isolated mains frequency measurement, temperature, linear travel and magnetic flux density.