not measuring voltage

[jyot445]

hi,

i have a vi which was previously sourcing voltage and measuring current with keithley 2420;it works fine.now i made some changes and sourcing voltage and measuring voltage,but its unable to do (rather measuring current again).

will you guys please check it and tell where the command is wrong.

[ainnrc · Accepted solution]

Hi,

I think its a primary rule in test development that to be able to measure current, you must source voltage. Vice versa, if you want to measure voltage you must source current. So if your goal is to be able to measure voltage, please source current instead as sourcing and measuring the same parameters theoretically should not work.

[Bob_Schor]

Have you looked at your post?  Would you like to look at such a tiny picture, or would you prefer to have the actual LabVIEW Code that would allow you to see things "full scale" (though probably much too big for a laptop screen, but that's what Editing is for)?

For those of us who are not Engineers, and/or may not be familiar with the Keithley 2420, could you explain a bit more what you are trying to do?  [Perhaps if I could see the Block Diagram and Front Panel, I could figure it o.ut, but it's much simpler when the Original Poster states the problem clearly ...].  I'm guessing you are using the Keithley to (originally) provide a source of (constant?  programmed?) current to a circuit and used (something?  the Keithley?) to make Voltage measurements.

Now you are using the Keithley to make (constant?  programmed and variable?) voltage for a circuiit and are measuring voltage (somethere else in the circuit) with something (the Keithley?  something else?).  While I'm not an Engineer, I do know you can have a voltage source (say, a battery or 110v AC) powering a circuit and make voltage measurements (voltage drops) -- I've even done this a few times.

Once we have a better idea of what you are trying to do, and have your VI in front of us, the chances are good we can either ask more pointed questions or suggest possible solutions.

Bob Schor

[bseguin]

Little suggestion, you should use the driver

http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=1587

Benoit

[jyot445]

@Bob_Schor

here is the vi(2018)

[cstorey · Accepted solution]

You cannot both source and sense voltage at the same time.  You can however, source voltage and sense current but also measure the voltage you are sourcing.  Unfortunately, the voltage is sourced at the meter and there will be voltage drops associated with parasitic (cable and connector impedance, impedance mismatch between source and device, etc.. ) before your device.  You cannot account for these drops if you are sourcing voltage, and even measuring the voltage you source will not show these loses.

I do suggest you use the Keithley 2400 driver - http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=1583

The example "Keithley 24XX Sweep and Acquire Measurements.vi" will show you how to set things up properly to source voltage and sense current but also measure the voltage.

Craig

[JÞB · Accepted solution]

As mentioned above,  use the LabVIEW driver.

I happen to know offhand that this device always returns voltage,current from a read.  So you're going to get current every time you index element 1 from your reading array.  Voltage is at index 0.

[jyot445]

TO  all of you who has helped me in figuring it out the correct way;THANK you.I got it working