Academic Hardware Products (myDAQ, myRIO)

cancel
Showing results for 
Search instead for 
Did you mean: 

mydaq voltmeter ammeter at same time

Solved!
Go to solution

Hi,  helping make a battery charge and discharge lab on mydaq running labview 2012 under windowsXp/7.  Have a vi

to read simultaneous voltage current and voltage from the mydaq ports.  The currents are up to 0.7 A so need to use

the ammeter rather than a0. 

 

The problem is, when I read with the ammeter, it agrees with fluke meter perfectly, but when I hook the voltmeter to the same ground I get different results on the ammeter (sometimes very different).  I have searched a bit and have found no other examples of people using the voltmeter and ammeter at the same time. 

 

I attached the code and the different measurements.  This was the case of a 6.5 V battery pack hooked in series with

a 45 ohm resistor on the ammeter.  The volt meter was hooked across the battery pack so that simultaneous readings

could be taken. 

 

1. is there a calibration Im missing?  Or a setting in the vi?

2. is this feasible with a mydaq?

3. if not, is there a better solution such as elvis protoboard?

 

 

Download All
0 Kudos
Message 1 of 5
(6,857 Views)

jvpjohnny5,

When I open your code, I see that you are using 2 different DAQ assistants. Is there any specific reason for this? You can probably use one DAQ assistant with one current channel and one voltage channel which should help to simplify things.

Here are a couple KB's that I just wanted to verify you saw. If you have already looked at these, great. If not, they should be a huge help.

Measure Current Using NI myDAQ

Measure Voltage Using NI myDAQ

Douglas Choisnet
0 Kudos
Message 2 of 5
(6,834 Views)

Thanks for your prompt reply.  I tried using a single DAQ Assistant and got this error.  Both the voltmeter and ammeter are running off the dmm channel.

 

0 Kudos
Message 3 of 5
(6,825 Views)
Solution
Accepted by jvpjohnny5

jvpjohnny5,

From what I can see, what you are trying to do can not be done. You are trying to use the one DMM portion of the myDAQ for 2 different resources which is not allowed. To verify this, I replicated the set up and tried to run both resources at the same time and it isn't allowed. The myDAQ is able to run one or the other, not both correctly at the same time. This is most likely the reason you haven't been able to find other people with a similar question.

Douglas Choisnet
Message 4 of 5
(6,791 Views)

True, but my original post had two different daq assistants access both volt and amp off the dmm.  Somehow it works, but

I'm guessing now that it should not.  Thank you for your input. 

0 Kudos
Message 5 of 5
(6,782 Views)