Measure voltage with NI 9215

[johndoe419]

Hello,

I have a power adapter as shown in the attached image which powers my embedded system. I would like to measure the voltage on the DC power plug at the end of this power adaptor (DC power plug connects to the DC power jack of the embedded system). Can I use NI 9215 (screw terminal) for this. I am afraid, the voltage range is only +/- 10V. The power adapter outputs around 19.5 V. Please let me know.

Thanks a lot.

[crossrulz]

You will want some external circuitry to bump down the voltage that is sent to your Analog Input.  Usually a simple Voltage Divider (I would probably just use 2 100kOhm resistors to divide by 2) and a Voltage Follower setup (op-amp with a gain of 1, useful for lowering the input impedence of your signal).

[johndoe419]

crossrulez@ So, the voltage readings are then multiplied by 2 to get the actual values right? What would be the approximate error rate like, in this case rather than monitoring the direct values?

[crossrulz]

Monitoring the values directly will just saturate your DAQ, possibly damaging it.

The accuracy of the voltage divider will be based on your resistors.  The op-amp should not add much error.  So your measurements should still be quite accurate.

And, yes, you will have to have a 2x scale to get your actual reading.