Multipoint acquisition with PXI 4071

[Dennis Chau]

Hi guys,

I am using the DMM 4071 to continuouly measure DC current input (let's say 5 samples ). According to help file, "Configure the trigger source with niDMM Configure Trigger and the trigger source polarity with niDMM Configure Trigger Slope. Use niDMM Configure Multi Point to configure the sample trigger source, trigger count, and sample count. Use niDMM Configure Sample Trigger Slope to configure the sample trigger polarity."

But when I check the example program, "Acq & Graph Multiple Samples.vi", it does not use niDMM Configure Trigger, niDMM Configure Trigger Slope, niDMM Configure Sample Trigger Slope.

Basically , I am not clear how PXI 4071 know: when the input change from, for instance, 1mA (1st value) to 2mA(2nd value), and acquire the 2nd value.

Thanks !

[KateB]

Hi Dennis,

4071 doesn't support analog level trigger.

It only supports digital trigger via auxilary input.

Therefore, you cannot configure it to start measuring at 2mA.

You need to keep on acquiring and filter out only the portion you want.

Regards, Kate

[Dennis Chau]

Hi Kate,

Thanks for your reply.

You mean that if my input are 1mA, 2mA ...5mA and changes every 100ns, there is no way that PX4071 can detect and acquire these 5 values, do you ?

If it's true, could you please explain more on how to filtering and keep the desired part ?

Thank you so much

[KateB]

Hi Dennis,

Nope, triggering and waveform acquisition is a different story.

You can perform waveform acquisition without triggering.

4071 will start acquisition once you start the task without triggering needed.

However, be remind that 4071 can perform up to 1.8MS/s at 3 digits resolution only.

Therefore, if your current change every 100ns (10MHz), 4071 will not be able to detect all changes.

Note, the result of waveform acquisition will be returned as a waveform.

You can use get waveform components function to get data array, and use array function to manipulate data the way you wish.

Regards, Kate

[Dennis Chau]

Hi Kate,

But in fact what I want to do is that 4071 only acquire 5 values only (1mA 2mA ..5mA).  Will the Interval Sample Trigger useful ?

Sorry, I am waiting for hardware components, otherwise won't ask so much

Thanks