Simultaneous Readings on a dmm - Please Help!!!

[eceone]

Hello, I am writing a program to control the 34401A 61/2 digit multimeter using instrument driver in Labview 7.0. I am writing to find out if it is possible to write a program such that I am able to view simultaneous readings without having to specify individually with the click of a mouse. I am using the configmeasurements.vi file as provided by the driver and right now I am able to view readings individually. For instance, I am able to view the DC voltage measurent but then If I wanted to view the current readings, I have to change it to read that. Is it possible to view bothe the voltage readings and current readings at once? If so, any hints as to how to approach that is much appreciated. Thank you.

[Dennis_Knutson]

You have posted to the wrong board. This is for NI DMMs.

Your question is confusing. Obviously the instrument is not capable of measuring current and voltage simultaneously just read the manual. You have to sequentially do that. If you have separate indicators, then there is no problem with viewing the sequential measurements.

[memoryleak]

Eceone,

Although I can't be certain without taking a screwdriver to a 34401A (and I curiously only have NI DMMs at my desk), it's extremely likely that the current measurement function shares circuitry with the voltage measurement function. http://www.ehow.com/how-does_5196572_multimeters-work.html  (First few paragraphs through "DC Current Readings").

If it is as suspected (current measurement circuits are shared with voltage measurements), then the only way to get a truly simultaneous reading is with two instruments.

It's important to decide just how tight you need "simultaneous" to be:

1) I've never used a 34401A through labview, but it may be possible to write a program that requests a voltage measurement, and then tell it to switch to current mode and take a current measurement.  This will probably require some amount of time to perform the switch and even more to allow the measurement to settle, but would keep you from having to click your mouse.

2) If you DO have two instruments (one sampling current and one sampling voltage) you may need to synchronize them so that they sample at exactly the same time (again, you'll need to decide how tight "exactly the same time" needs to be)

I hope this helps!

Hugs,

memoryleak

Message Edited by memoryleak on 09-17-2009 03:40 PM

[eceone]

Thank you memoryleak. That was a lot more helpful than the earlier response. It doesn't have to be simultaneous(my apologies for using that term loosely). I just basically want to display it on the same front panel in labview. For instance, I want to be able to display both frequency and voltage readings on the same front panel (kind of similar to how an oscilloscope is able to display both voltage and frequency readings on the same screen.

Thanks in advance for your help. 

[memoryleak]

Eceone,

Great!  It sounds like you'll be able to implement your solution in software 🙂   You may be able to adapt the examples here (I think this is the right driver) fairly easily: http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=014E7F05D12C6F8BE0440003BA7CCD...

It may be as easy as calling "Configure Measurement" and "Read Measurement" twice (once for each type of measurement). 

Hugs,

memoryleak