Shunt Resistors in Conjunction with Switches for Measuring Current with an NI-DMM Hardware: Switches, Modular Instruments>>Digital Multimeters (DMM)
Problem: I have a current shunt module (shunt resistor) that I’m using with an NI-DMM for measuring high levels of current, but I want to toggle between multiple current readings through the use of a switch with the shunt. Can I do this? Solution: To do this you would have your shunt connected through the switch to the different current sources. The shunt should be connected to the common line and the current source will be connected to the correct channels. The current reading is calculated by measuring the voltage across the known resistance. Any lead resistance introduced by the traces and the relays in the switch creates a voltage divider. This is not important however, as the current source will maintain the current in the circuit. As a result, the current at the DMM will not change. If the current being measured is coming from a voltage source, a voltage divider could be introduced. This can be protected against by using a 4 wire measurement, which will take into account the switch path resistance. When setting up a DMM and switch system for high current measurement make sure to take into account the switch can only handle so much current. General-purpose relay modules provide the highest current throughput. They do have a lower rate though. The RF switches have a high rate and respectable current input range. Related Links: CSM Installation Guide General Purpose Switch Modules RF Switches Attachments:
Report Date: 12/12/2006 Last Updated: 05/15/2007 Document ID: 44BJPPBE |
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