Keysight U1232A multimeter mA/uA measurement

Thread Starter

killerfish

Joined Feb 27, 2009
29
Hi All,

I bought the above meter not long and realized this meter has 2 issue really make me puzzled. I had used other meters like fluke and tenma, but this one, I cannot figured out why. Anyone do you have any experience or used this one care to enlighten me?

First issue:
Jumpy probe, reading cannot settle quick and sharp. I switched to my fluke probe, it show the unit was working good. So the probe is quality or compatibility issue? Or something else?


Second issue:
The microampere measurement accuracy has blown out of my expectation. A microampere function that cannot measure microampere accurately seriously? Refer to my table of measurement, the microampere measurement with this meter is so way out of the range compare with my reference meter(which is a little better in accuracy). It is many multi times over the expected values.





If I have a circuit power with 2.13mA. According to the spec and the calculation, I should expect my measurement should fit within the tolerance below? No?

Tolerance range
=% of reading + count * resolution
= 1% * 2.13mA + 2 * 0.1uA
= 0.0215mA

Aside that, this meter couldn't measure 0.6mA to 1mA, a shadow zone. Damn god regret bought this meter.

Your advise is greatly appreciate
 
Last edited:

AlbertHall

Joined Jun 4, 2014
12,345
From the spec above, on the uA ranges your meter needs up to 2.5V and that is a large part of the 5V you are using to drive the current and so I suspect that the current reading is accurate but the meter will reduce the actual current flowing. To prove this, connect both meters in series with the 470Ω and see how well they agree then.
 

ModemHead

Joined Nov 1, 2010
13
I think this particular DMM model is targeted for HVAC technicians. The uA range is for testing flame sensors. It has a relatively high resistance shunt, and thus a high burden voltage. It's not well-suited for general electronics work, at least in terms of the current-measuring capability. The Fluke 116 is similar in these respects.

As for the probes: surface film, different shapes, metal platings and alloys will affect the resistance of a connection made with just light hand pressure. A decent meter should react to the variations. I would recommend to evaluate probes in actual use, ie. see if they work as expected by checking a copper trace on a PCB or somesuch.
 

Thread Starter

killerfish

Joined Feb 27, 2009
29
From the spec above, on the uA ranges your meter needs up to 2.5V and that is a large part of the 5V you are using to drive the current and so I suspect that the current reading is accurate but the meter will reduce the actual current flowing. To prove this, connect both meters in series with the 470Ω and see how well they agree then.
I think this particular DMM model is targeted for HVAC technicians. The uA range is for testing flame sensors. It has a relatively high resistance shunt, and thus a high burden voltage. It's not well-suited for general electronics work, at least in terms of the current-measuring capability. The Fluke 116 is similar in these respects.

As for the probes: surface film, different shapes, metal platings and alloys will affect the resistance of a connection made with just light hand pressure. A decent meter should react to the variations. I would recommend to evaluate probes in actual use, ie. see if they work as expected by checking a copper trace on a PCB or somesuch.
Don't have an extra meter to verify the current measurement in series but will get it to test later on. I opened up an old broken multimeter and probe different part of the metal around, you are right, only certain material I will not get jumpy reading from a short circuit measurement. The probe work good on copper trace, not good on surface for some resistor lead.

I guess I will need to get another new meter for my microcontroller work. I will need one that really can measure uA and mA when MCU sleep. Any recommendation for meter or any extra tips to purchase for my purpose, for electronic works? I felt silly, using multimeter for long, and didn't really into understand them.
 
Last edited:

ModemHead

Joined Nov 1, 2010
13
I guess I will need to get another new meter for my microcontroller work. I will need one that really can measure uA and mA when MCU sleep. Any recommendation for meter or any extra tips to purchase for my purpose, for electronic works?
For measuring really low microprocessor currents, look for DMMs with the lowest possible burden voltage, ie. the lowest resistance shunts. You may also want to look into Dave Jones' µCurrent device or one of it's open-source equivalents.

As for leads, IMO probes are only good for actual probing. Thin sharp ones for poking at PCBs, and a sturdy less-sharp set for general electrical/automotive type work. For testing components, or to maintain a hands-free connection, it's really handy to have a few sets of fairly short leads with alligator clips and/or mini-grabbers on one end and 4mm banana plugs on the other. A more expensive alternative might be to get a full kit of "modular" test leads. In the US, Probemaster is a good source for decent test lead sets.
 

rsjsouza

Joined Apr 21, 2014
383
Whatever ModemHead mentioned. Like the UT61E or the common M830B clones, the U123x meters have 1kΩ shunt for µA currents, which is pretty high for this particular application. If you are willing to invest in a µCurrent, it really works well with any meter, even your U1232A - if not, you can always put a 10Ω resistor in series and measure its voltage drop, which will be in the range of 20mV - something that is easily measured with the 600mV range of your meter.
Also, if you are using one of TI's microcontrollers, you can also make use of the EnergyTrace, which has quite reasonable resolution and goes sub-µA. A video is shown here and there is a variant here.

The U1232A meter is very well built and should be fine for your work in general but, if you are really not satisfied, they tend to hold value pretty well - you can always sell and get something different.
 
Check each individual test lead. e.g.

Use Resistance scale, non-autorange, low ohms.
Plug one lead in to meter.
Touch probe to other binding post on meter.
Flex leads - particularly at the ends.

Repeat with other probe.

If both are unstable, use a bent paper clip and/or known good probes.
 
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