Need to monitor 2 high current sources in real-time with precision

[TurboLS]

I have a computer from NI with LabVIEW and I wan't to use it to monitor currents in real-time for testing fuses. As such, something like a DMM would be good, but it has to be able to monitor currents in the ball park of 300A and do it with a few decimal places of precision. I would like to use this hardware with something like NI Scope, so I can view the two plots in real-time side by side. Any and all input is appreciated. Thanks.

[RossC]

TurboLS,

While we do not have a board that directly measures a 300A current, a measurement like this can be accomplished with our DMM or Scope boards using a current clamp. This is a transducer that is placed around the current carrying wire which translates the large current in the wire into a voltage readable by an instrument. A typical translation for a high current application might be 1 mV/A. You can find current clamps from a number of third party vendors. Click the following link for a Google search on current clamps: Google Current Clamp Results. Have a good day!

Sincerely,

Ross C
Applications Engineer

[Buechsenschuetz]

A current clamp is not a bad option for measuring high currents. It also provides complete isolation of the circuit to be measured and the measurement device.

Many current clamps on the market are suitable for AC measurement only. Check carefully whether a certain item is suitable for DC current measurement. I have made good experience with LEM current clamps.

All DC current clamps need a power supply, in most cases a small battery. Of course they can also be powered by wall transformers (with regulated output if possible) or external power supplies.

Some manufacturers also make current transducers which can be integrated into systems, I think LEM makes them, too.

If you do not need galvanic isolation you can also use shunts. Shunts usually cause 100mV voltage drop differential voltage between terminals (60mV in Europe) for the rated current, e.g. a 500A shunt will have an 'output' of 100mV@500A. However, as mentioned, the output voltage is NOT isolated from the circuit to be tested.