Impedance analyzer module of Analog Discovery 3 does not work properly. Need help here :)

[Dr.Zool]

Hey there crew and people using Digilent Products

I recently purchased an Analog Discovery 3 and the Impedance analyzer module/adapter for some electrochemistry experiments at our University (Department of Chemistry, University of Crete, Greece).

I have found a couple of problems that I need help to solve.

#1 : There seem to be some bugs in the Waveforms software or some malfunction in my IA adaptor because only the 100 Ohm and 1M Ohm reference resistors work (sometimes). I am still testing the Instrument measuring High precision metal film resistors and the only reference resistors that give correct results are the 100 Ohm and 1 Mohm resistor. The other resistors always give wrong data. I have witnessed two cases of wrong data. The data have the correct morphology but are for some reason scaled by some factors of 10 eg 10k resistors show constant Impedance and 0 phase along the 1Hz to 1MHz frequency range but instead of 10k I read 1k 100k or some other value depending on the value of the Reference resistor. The second case is even worse, the data have completely wrong morphology eg a 10k resistor gives resonator-like data. 

Sometimes even the 100 Ohm and 1Mohm resistor don't work because it gets stuck in one of them and when I change them from the waveforms software they don't change. Sometimes I can hear the switches changing sometimes not.

The Instrument is new I only have it for a couple of days. What is going on here can anyone explain to me how to deal with this?

Is this some communication problem between the waveforms software and tha analog discovery 3 or is this a malfunction of the IA adapter.

[attila]

Hi @Dr.Zool

Like every devices each adapter is tested with a load to make sure the drivers, relays and resistors are ok.
Try using other USB port, powered hub or the latest version which add better USB supply insufficiency detection for AD3:

 

[Dr.Zool]

Thank you attila for the answer.

I downloaded the latest beta version.

I am kind of getting similar results though.

The DUT is a 10k metal film resistor, the reference is 10k resistor from the impedance analyser. The results are shown below and are completely weird to me 

eg 

[Dr.Zool]

Also as you can see below the values I get depend strongly on the reference resistor I use for example

10k DUT

10 Ohm reference, Amplitude = 1V



100 Ohm reference, Amplitude = 1 V 


1 kOhm reference, Amplitude = 1 V


10kOhm reference, Amplitude = 1V


100 kOhm reference, Amplitude = 1V



1 MOhm reference, Amplitude = 1V




As you can see the results are inconsistent and only the 100 Ohm and 1 MOhm resistors give correct measurements

Do you think this is a power-related issue? Do I need a powered USB hub or an additional 5V power supply or something?

I am trying to find out what's going on so that we can use it correctly in the lab.

Best regards
Kostas



 

[attila]

Hi @Dr.Zool

Maybe AD3 V+ is not providing 5V or there is a problem with the IA adapter like one of the relay drivers is bad or it consumes a lot of power and the voltage drops, in this case it should also heat up...

I was only able to reproduce some relays to not switch, just by lowering the V+ voltage from the software code.

Please check the V+ voltage in the Supplies tool: without adapter (V+ controlled from Supplies) and with adapter connected (V+ controlled by IA interface).
Also the power consumptions (USB Current) should not increase by much with the adapter.
You could also verify the V+ voltage (top 3rd/4th pins) on the header or the C3 capacitor on the adapter.