myRIO current measuring

[Zillion]

Is there a way to measure current with the myRIO platform?

[Wolfgang_Z.]

Hi Zillion,

There is no input on NI myRIO to measure current but you can easy measure current with a Shunt Resistor or a Hall-Effect-Based Linear Current Sensor IC.

You get a Shunt Resistor in every electronic shop. If you are looking for a Hall-Effect-Bassed Current Sensor you can use e.g. ACS712 from Allegro. Especially for high current measurement I would prefer the Hall-Effect Bassed Current Sensor. If search in web for ACS712 you find a lot of ready to use boards with the AC712 IC.

Best Regads,

Wolfgang

 

[Wolfgang_Z.]

Current Measurement with NI myRIO

[Zillion]

I have the ACS758 by Allegro, but can't find a calibration equation for it and don't have the equipment to provide a constant variable current for my own calibration. The link that you provided for measuring current with a shunt resistor looks very helpful! Thank you!

[Zillion]

Are there recommended values for RL and Rs?

[Wolfgang_Z.]

For ACS758 you find the Sensitivity (mV/A) auf page 2 in http://www.allegromicro.com/~/media/Files/Datasheets/ACS758-Datasheet.ashx.

RL is the Load resistance of your device (for example a motor).

RS is the Shunt resistance. RS depends on the current range you want to measure.

R = U / I

Assumed you want 1 V for the highest current value and the highest expected current value is 2 A than you should use a resistor of 0.5 Ohm.