Digilent Analog Discovery 2 as a resistance meter. - Page 1
Forum section: electronics / testgear

author: PeterFW
author_rank: Frequent Contributor
timestamp: December 22, 2023, 01:22:52 am
content: I am trying to build a improvised 4 wire resistance meter with a Digilent Analog Discovery 2 and i am wondering is i am missing anything obvious here or if this approach is terrible.This is just to learn and experiment, to see if this would be possible and how well it might work.Basically i have 2 differential ADCs, a programable power supply and 16 digital IO pins that i can program.My basic idea was to just buy a decent reference resistor on the power supply to get a somewhat stable and and adjustable current source.And ADC1 goes across my reference resistor, ADC2 across my DUT with proper kelvin probes.I can measure the current over my reference resistor and the voltage across my DUT.I found this 100 Ohms ±0.02% ±0.2ppm/°C resistor, bit worried that there is no solder profile in the datasheet but a standard temp profile should not disturb it too much.https://www.digikey.de/de/products/detail/vpg-foil-resistors/Y1630100R000Q9R/4231501Already have a bunch or proper resistance meters around to check it against, to make some comparisons how well that works.Maybe a passive lowpass filter on the ADCs might not be a bad idea with a jumper to see how it impacts the measurements.

author: croma641
author_rank: Regular Contributor
timestamp: December 22, 2023, 12:22:57 pm
content: Peter,Your solution is->https://www.eevblog.com/forum/projects/impedance-analyzer-build-and-experiments->(and all the other videos)a pcb, few € of components , fantastic solution for capacitors, resistor, impedances....one of the most underrated project ever seen (100% working), super precisebyeAndrea

author: egonotto
author_rank: Super Contributor
timestamp: December 22, 2023, 07:23:56 pm
content: Hello,I think the accuracy of the voltage measurement of the Analog Discovery is not sufficient for a ±0.02% resistor.WaveForms already has an impedance analyzerBest regardsegonotto

author: croma641
author_rank: Regular Contributor
timestamp: December 22, 2023, 09:03:12 pm
content: If advanced VNA correction algorithms are implemented, with an active plugin, as in this case, the result is very different"Impedance analyzer" was created to overcome the deficiencies of "Waveforms"Please read the whole abovementioned thread.regardsQuote from: egonotto on December 22, 2023, 07:23:56 pm

author: G0HZU
author_rank: Super Contributor
timestamp: December 22, 2023, 09:45:41 pm
content: QuoteI agree. I've been using the AD2 and this SW (by TheStuffMade) for quite a while now.I mainly use it to measure lumped components across LF through to about 100kHz.It really is a great piece of work and I'm very grateful for it.

author: egonotto
author_rank: Super Contributor
timestamp: December 22, 2023, 09:56:12 pm
content: Quote from: croma641 on December 22, 2023, 09:03:12 pmHelloPeterFW has been looking for a 4 wire resistance meter with a Digilent Analog Discovery 2 and not asked for a VNABest regardsegonotto

author: croma641
author_rank: Regular Contributor
timestamp: December 23, 2023, 05:10:47 am
content: Dear Egonotto,The "Impedance Analyzer" plugin IS part of a 4 wire measurement system WITH advanced VNA correction algorithms !Quote from: egonotto on December 22, 2023, 09:56:12 pm

author: egonotto
author_rank: Super Contributor
timestamp: December 23, 2023, 11:00:40 am
content: Hello,I have no doubt that the Impedance Analyzer is very good.Best regardsegonotto

author: croma641
author_rank: Regular Contributor
timestamp: December 23, 2023, 04:38:52 pm
content: OK