Use DAQ to provide multimeter diode test functionality

[eoinbutler]

Hi,

I'm trying to use an NI-USB 6009 to measure the voltage drop accross a diode, in the same way that a digital multimeter does. If I understand it correctly, these normally work by driving a known current through the diode and measuring the voltage drop.
I can think of a way using the analogue output of the device to drive a resistor + diode in series, reading back the resistor voltage to figure out the current and adjusting this until it's right, but that's somewhat convoluted and might take a bit of time (this is supposed to be integrated into a far larger system). Does anyone know of an easier/better way?

Cheers,
Eoin

[Johann.Wagner]

yes correct you must send an analog output voltage (e.g. array of values rising) and then measuring the current (analog input current or voltage via shunt resistant or current-voltage-amplifier) - attached here an example. Only change the simulated values with your array of values and change the polymorphic vi from waveform output to samples of double values like in the screenshot it attached here additionally

Best Regards

[Johann.Wagner]

the screenshot with changes of standard example for simultanously input and output

[Johann.Wagner]

if you are using cvi or c programming you find the examples in cvi (find examples -> analog input/output or synchronizing) or when installing daqmx from our side

www.ni.com/support -> drivers and updates -> daqmx e.g. 8.7.1 version - then find daqmx visual c examples

under C:\Programme\National Instruments\NI-DAQ\Examples\VisualC\Ai

and C:\Programme\National Instruments\NI-DAQ\Examples\VisualC\Ao

you can run analog input and output examples parallel - then shoud be the same

Best Regards