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Multimeter selection for production testing

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mawyatt:
If one is measuring on 100uA scale (standby) with a DMM and the DUT then demands 2A (becomes active at turn on), wouldn't the DMM burden voltage max out until the DMM could auto-range or follows command range change to the higher current range?

If so this would starve the DUT of voltage and as mentioned likely incur a reset!! Maybe a low drop SBD across the DMM could prevent the reset by allowing the initial higher "turn on" current to flow thru the diode while the DMM auto-ranges or followed commanded range change, while keeping the diode current insignificant during DMM measurements as the normal DMM burden voltage is low enough not to allow much diode current.

Also consider an "Active Clamp Diode" if you have a control line available. Here a simple Power MOS (P or N depending on where it's located) device shunts DMM terminals and is active when transitioning from standby (100ua range) to active turn on (2 amp range).

Best,

bdunham7:
Unless I've missed something, none of these meters mentioned--not even the unaffordable Keysight--can do what you are asking for.  You need to measure 2A on the 10A range but even a long-scale meter isn't going to measure to 10µA accuracy on that range--that would be 1ppm. Everything talked about so far has a separate circuit for the 10A range, so how is the meter going to 'switch' between those ranges?  There are older meters that either have single current ranges with 0.1R shunts instead of 0.01R, such as the Fluke 8842A or multiple shunts with a single input such as the HP 34401A.  I just tried both of them. 

The Fluke 8842A will do what you want except it is limited to 1.99999A and relies on amplification to create a 200mA scale that amazingly enough can measure 100µA as accurately as you need (in my test) but is not specified to be that good.  It is also GPIB-only.

The 34401A works, has the single input with multiple ranges/shunts (3A/0.1R and 10mA/5R) and is specified to easily meet your needs.  However, it does not have make-before-break when switching ranges.  It's quick (a double-pole relay switches over) and you could probably deal with it by using a bypass capacitor and not using autorange but rather ranging up (via software control) before applying the 2A current.  The 34401A has RS232 that can be adapted with a USB cable and the command set is sufficient to do the simple task you're requesting.  The only remaining issue is burden voltage which is about 900mV @ 2A. 

Edit:  I just looked and I was wrong about the current inputs on the Siglents.  And the 34465A lower range current input is actually 3A.  So the Siglent 3045X works just fine except you'll have to check the make/break operation between ranges.

2N3055:
In automated test where you control both instrument and test equipment it is simple to create test code for DUT that will work in synch with test flow and switch meter in proper range before drawing large current.
That would be sufficient to verify operating modes and hardware.

tszaboo:

--- Quote from: mawyatt on April 25, 2024, 03:37:05 pm ---If one is measuring on 100uA scale (standby) with a DMM and the DUT then demands 2A (becomes active at turn on), wouldn't the DMM burden voltage max out until the DMM could auto-range or follows command range change to the higher current range?

--- End quote ---
Oh believe me I know this issue. Constant problem for firmware validation, the current changing 3-4 magnitudes. We have a Keithley 2280S that will do this with reasonable accuracy. But you do it exactly like this:

--- Quote from: 2N3055 on April 25, 2024, 04:00:02 pm ---In automated test where you control both instrument and test equipment it is simple to create test code for DUT that will work in synch with test flow and switch meter in proper range before drawing large current.
That would be sufficient to verify operating modes and hardware.

--- End quote ---
In the end you only need 2-3 values to verify if a device works properly. Idle current at different power supplies enabled, and peak currents during RF.

mawyatt:
The KS34465A and SDM3065X have no problem handing these current ranges for a single set of terminals. KS has a 3A max terminal that also supports 1ua range (as well as a 10A range on another terminal) and the SDM has 10A terminal that supports a 200ua range.

Also the DMM6500 terminal that surrorts 3A and 10ua range.

We just checked all of these to be sure :-+

Best,

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