MyDAQ

[abend037]

Hello:

I'm having problems with myDAQ. I'm not getting any current when I build a simple circuit with a resistor (I measure current in series) . Secondly, when I set up MyDAQ to give 5 V as source, it gives that Voltage but when I close the circuit it gives me half of it ( again I measure Voltage in parallel ). I tried it again with my professor and my teammates the same lab and it still has the same problem. At the beginning, it read the voltage and the current but the current gave the wrong measurement. In addition,when we went to build the second lab, when it was a closed circuit the voltage wasn't the same, example: if we set up the voltage source for 5 V it gave us 0.3 V or when it was 10 V  it gave us 2.3 V.If the circuit was open it gave us the correct voltage. Now also Mydaq doesn't read current at all (Amperes). Moreover, we built the same circuit with a physical battery of 6 V and we measured the Voltage with myDaq it gave the same result, the voltage wasn't the same as 6 V. 

However, when we measured the voltage and current using an Multimeter it gave us the right units . Please I need to solve this issue.

Thanks

Alfredo 

[natasftw]

How old is the myDAQ?

You mentioned a classroom setting.  Have you tried using a peer's myDAQ to measure the same circuit?  Do they get readings that match yours or readings that match the DMM?

Are you using the AI channels or plugging leads into the myDAQ?

[abend037]

it's been a month since I have had myDAQ and I tested the same circuit with a peer's MyDAQ and he got the same problems as mine. That's why I am worried because it's too much coincidence that both have the same problem. In addition, I conncected  leads to the terminal connector that is attached to MyDAQ. I connected a lead wire to a AO ground and another one to 0. 

[Fernando_D]

Hi there,

You mentioned you are using a terminal connector attached to myDAQ, this terminal connector was included with the myDAQ? Model?

Just to clarify, are you getting wrong measurments using the DMM probes or using the Analog Input channels?

Follow the steps on this tutorial to take a battery voltage measurement using the DMM probes:

Take Your First Measurement Using NI myDAQ and NI ELVISmx Instruments

Let me know how this works.

If this works try to take a current measurement. Use something basic like the battery in series with a resistor. Open the circuit and take the current measurement using the DMM probes.

Looking forward to hearing back from you.

Fernando

[abend037]

Hello Fernando:

The terminal connector was indeed included in myDAQ and I'm not getting any current using DMM. I Do get voltage of the circuit using myDAQ. I set up the circuit using a batery of 9 volts  with a resistor of 150 ohms and I did not get current at all (Measuring current in series).  

[Fernando_D]

Hi there,

For the current measurement, make sure the black DMM probe is connected to the COM terminal on the myDAQ. The red probe to the HI(A) terminal. Sorry for the low level details,  I just want to take into consideration all the posibilities.

The myDAQ has an internal fuse, it would be good to test it. Open the NI myDAQ User Guide, and go to the NI myDAQ DMM Fuse Replacement section. Follow the steps to tes the fuse and let me know the outcome.

[Donovan_B]

It does sound like it might be a fuse problem for reading current. As far as the first post when you output 5V and only got 0.3 once the circuit was closed, were you using the 150 ohm resistor you mentioned in your last post? The AO channels of myDAQ have a maximum current output of 2 mA as noted in the NI myDAQ Specifications. If you were using the same 150 ohm resistor, 2 mA * 150 ohms = 0.3 V. It's likely in that scenario you were drawing the max current for the channel, so the voltage output had to drop.

If you need more current at 5 V, you can use the 5V supply on the myDAQ, which has a maximum output current of 100 mA.

[abend037]

hello Fernando:

When I measured it ,everything was connected the way you explained it to me. Now, on the myDAQ manual , it states to use banana cables to test the fuses. Instead, I used the DMM test leads because I don't have any at this moment. When I tested the fuses for the current . I had to connect the red probe to the HI (A) and the black in the COM and then click on the icon resistance (ohm). Moreover, when I clicked "Run" it read +Over so it means I need to change the fuse . Am I right? thanks

Alfredo

[abend037]

 Hello Donovan:

I don't remember which resistor I was using but it was definitely a resistor with small resistance. Thanks for that information but now myDAQ is not reading current ,not even for a simple circuit. I tried to figure out whether it was the fuse and indeed, it seems to be it the issue. Hopefully I can get it back to work.

Alfredo