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Keysight U1282A & U1242C Cat III/IV Waterproof True RMS Digital Multimeters The new U1282A DMM from Keysight provides a number of enhancements over its predecessors, including IP67 dust/ water ingress protection, longer battery life (800 hours from four AA cells), 3-metre drop resistance and a 60,000 count display with a basic DC voltage accuracy of 0.025%. The U1242C is a lower-cost option with similar features, including IP67 protection. Review by Nicholas Vinen W E’VE BEEN USING the U1252B and U1253B DMMs in the SILICON CHIP office for a number of years now and we like them. The U1282A appears to supersede these, in the sense that it offers similar features and precision but has been furnished with a number of improvements. It also employs a larger, more legible LCD readout without the option of the previous OLED display and having compared them side-by-side, we think the LCD is better. However, the most obvious improvement has to be the IP67 rating (waterproof up to 1m), which is good news for anybody who has to work outdoors or in a wet/dusty environment. The display is now a 60,000 count type (those we are currently using are 50,000 count) which means less auto-ranging and that can only be a good thing. One feature of our existing meters we don’t love is their rechargeable batteries. While this does avoid the need to open them up and buy new 60  Silicon Chip cells, all too often we find the battery goes flat in the middle of a session and we then have to wait for it to recharge. The meters reviewed here take a much simpler approach and use four alkaline AA cells. You do need to unscrew the rear cover to replace them but the battery life is now so long that you will rarely have to do that. Good. The U1282A claims to last up to 800 hours while the U1242C will run for 400 hours between battery swaps. Of course, if you make extensive use of the screen back-light or the inbuilt torch (on the U1242C), use the continuity buzzer a lot, etc, you will drain the battery faster. But given that most of the time a DMM is being used it’s probably just measuring voltage or current, you can expect either meter to last a long time on one set of cells. Both new units are tested to withstand a 3-metre drop onto an unspecified surface; presumably a hard one, since you can’t always arrange to have carpet or grass underfoot if you happen to drop them! This, combined with the IP67 rating, suggests that Keysight are trying to make these units attractive to electricians and technicians as well as R&D staff who would be using them in a lab environment. The main differences between the U1282A and the less expensive U1242C are the display count (60,000 vs 10,000), basic DC accuracy (0.025% vs 0.09%), battery life (800 vs 400 hours) and some differences in features (see below). Otherwise, they are quite similar in size/appearance and have the same voltage ratings of 1000V (Cat III) and 600V (Cat IV). Extra features The U1282A and U1242C both have a “Vsense” feature which means they contain a non-contact voltage sensor at the top of the meter which can be activated with a button press. The U1282A also has the ability to generate square-wave and PWM signals and siliconchip.com.au terface (U1173, pictured). The optical interface means that not only is the PC electrically isolated from the meter (and thus it’s safe to use it “live”) but also it does not affect the waterproof rating. In use has an optional low-pass filter for AC voltage measurements, to allow for accurate measurements of chopped mains voltage signals such as those used to drive induction motors from variable speed drives (VSDs). The U1282A has an AC bandwidth of 100kHz while its cheaper sister, U1281A (without Vsense), has a 40kHz bandwidth. The U1242C has 2kHz AC bandwidth. Other features the U1282A has that the U1242C doesn’t include dual display mode (eg, AC voltage + frequency) and support for probes with inbuilt pushbuttons for data hold/logging/saving. The U1282A also has up to 1µV resolution (compared to 10µV for the 1242C) and a wider capacitance measurement range of 1pF to 0.1F (rather than 100pF to 0.01F). Interestingly, the U1242C has some features not present in the more expensive U1282A models. These siliconchip.com.au include “Harmonic ratio” measurement which displays the distortion level for an AC signal and is intended for mains waveform analysis. It also has the ability to make differential temperature measurements using two thermocouples and a low-impedance voltage measurement mode to eliminate phantom readings from stray fields and capacitive coupling. Also, as mentioned above, the U1242C has a rear-mounted white LED torch. These extra features all seem intended to be useful for electricians and field technicians, which makes sense since the U1242C should do everything they need and its lower price makes it great value for such users. Both units have a data logging mode which allows them to store a number of readings to their internal memory, which can be later downloaded to a PC using the optional USB/optical in- So what are they like to use? The short answer is that they work very well for day-to-day measurement tasks. As already noted. the display is easy to read, with a very quick update rate and reasonably fast auto-ranging. The LCD bargraph at the bottom of the screen is quite handy for viewing rapidly changing readings. The ambient temperature display with 0.1°C resolution in the upper-right corner of the screen is also good. The volume of the continuity beeper is impressive and should work well in noisy environments and if you have one of the models with Vsense, a red LED at the top of the unit also lights to indicate continuity. Speaking of Vsense, you activate it by holding down the “Null” button for 1s and the LCD bargraph then shows the detected magnetic field strength. Once you bring the top of the unit close enough to live mains wiring, the beeper sounds with a particular cadence and the red LED lights up to let you know. The range switches have a nice chunky feel to them and all the modes are pretty easy to figure out; you would rarely have to refer to the user manual. Both units are supplied with probes with nice sharp tips and they look like they will stand up to a reasonable amount of abuse and possibly last as long as the meters themselves. Conclusion The U1242C offers great value as it is a quality meter with many great features and should suit casual users and electricians well. The U1282A is better suited for lab use with its higher precision and less need to switch ranges, thanks to the 60,000 count display. If you’re in the market for a quality/value or high-end portable DMM, either of these two units would be a good purchase. To purchase either unit, or make an enquiry, contact Keysight Technologies by visiting www.keysight.com or calling 1800 629 485. A list of their Australia/New Zealand distributors can be found at www.keysight.com/ main/partnerfinder.jspx?N=1+18763 SC 2+187535&cc=AU&lc=eng April 2016  61