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With resistors, it is working fine, but our devices are very sensitive to static discharge and something in the delta mode setup appears to be destroying them. I know it is the delta-mode setup because the nV meter registers any voltage buildup across the device prior to running the code, and can see that after attempting a differential conductance measurement the gap has blown (nV meter measures overflow voltage across terminals due to ESD.
I have put the commands I use below. Do you see any issues among them, in particular anything that might explain our device failures using the delta mode?
Please feel free to call me - message me for a number since this is a public forum (it appears to be your only means of contact). if it is possible to connect today that would be ideal. Thank you! Darin
I use Matlab via a GPIB connection to control the setup. If you want the actual code for matlab let me know.
I usually operate in the 10-150mV range, uA range, about 2-5 uA steps, similar deltas, 1NPLC integration time on the voltage measurement, 20 millisecond time delay to let it settle (I've found that's necessary, and more effective than the NPLC)
SYST:COMM:SER:SEND "VOLT:RANG:UPP ',num2str(vComp) ,'"
SYST:COMM:SER:SEND "VOLT:NPLC ', num2str(vRate), '"
fprintf(isrc, 'FORM:ELEM READ');
dIdV = str2num(fscanf(isrc));
fprintf(isrc, 'FORM:ELEM SOUR');
current = str2num(fscanf(isrc));
fprintf(isrc, 'FORM:ELEM AVOL');
voltage = str2num(fscanf(isrc));
- Keithley Applications
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What value are you setting voltage compliance to?
If you are measuring millivolts at microamps, I question the need for a delta-mode system. Indeed, if your device is sensitive to a spike, changing current quickly, which is what delta mode is, will induce spikes from any inductance in your cabling V = L * di/dt
My suggestion, using the front panel, is to set the 6221 to 0 amps on the appropriate microamp range, enable the output, measure the voltage with the front panel of the 2182A. This is your device+cables offset, V_o. Watch the voltage reading and look for drift, this will be cabling and connections thermal drift.
Slowly increase current via the front panel until you reach the maximum current you desire. Record the voltage V_1 and current I_1. Your device resistance = (V_1 - V_o)/I_1.
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