EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Pack34 on March 27, 2019, 03:30:20 pm
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I have an application where I need to ramp a resistive load from 10-ohm to 550-ohm and back down as part of a calibration routine for some ADCs. I was thinking of hooking up a couple DMMs and an electronic load to measure the voltage and current of the system as the load ramps up and down.
Would this work?
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The Rigol DL3021A shows a resistive load range from 2.0 - 15k, so in theory it should work. You probably don't need a DMM as it should show you current and voltage. It is certainly worth trying.
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The Rigol DL3021A shows a resistive load range from 2.0 - 15k, so in theory it should work. You probably don't need a DMM as it should show you current and voltage. It is certainly worth trying.
I'm looking at taking advantage of the 5ksps of the Keysight DMM I have, then wrap everything in an automated Python script.
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An electronic load needs considerable time to settle in CR-Mode and also requires some "macroscopic" current to flow (depending on brand/model), otherwise it cannot control the resistance. Also please consider that on all loads (that I'm familiar with at least -- which are Rigol, Maynuo and similar ones, Applent, Chroma), there's a considerable capacitance present across their input terminals.
If you need the resistance for small signal calibration, you may consider a different option like those digital trimpots (i.e. AD5270 (https://www.mouser.de/datasheet/2/609/AD5270_5271-1501568.pdf) or the like), maybe equipped with a floating supply / digital isolators. Or maybe, you can include these devices directly in your design to facilitate calibration.
If you need a set of fixed resistances, you may be better off (and possibly more accurate) if you use a set of fixed resistors / preset trimmers and a bunch of reed relays, or maybe an R-2R cascade to form a primitive resistive D/A converter.
Cheers,
Thomas
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This is a pretty common way to do things like this.
Here's an app note we just recently put together on eloads that might be useful. Direct PDF download:
http://bit.ly/eLoadAppNotePDF (http://bit.ly/eLoadAppNotePDF)
It's mostly focused around our new load, but has some useful info in it.
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Hi Daniel, do these new N6790 Series loads compatible with older N6705A/B series mainframes?
Pack34, sorry for jumping in your topic with a different question.
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Hi Daniel, do these new N6790 Series loads compatible with older N6705A/B series mainframes?
Given how recently the 6705B was discontinued you'd hope so, although given the final firmware for them still says Agilent I suspect it's unlikely.
Which is a shame. I have a 6705A, which could be excellent with just a few UI tweaks, until then it's useful for specialist things (to be fair, that was the goal), and the new load modules would go well in mine.