High-Current (Up to 10 A) Measurement Considerations
The NI 4065 and NI 4071 can measure currents up to 3 A, and the NI 4070/4072 can measure currents up to 1 A.
If you need to measure currents higher than the maximum range available, you can use the CSM-10A external shunt to measure currents up to 10 A. Refer to Measuring Current and to Related Documentation for the NI Digital Multimeters Getting Started Guide for more information about how to use the CSM-10A shunt with the NI 4065 and NI 4070/4071/4072.
When measuring high current values, you could get errors due to resistor self-heating. The NI 4065 and NI 4070/4071/4072 use internal shunt resistors with low temperature coefficients and good thermal resistance. Refer to the temperature coefficients in the specifications of each device for the effect of temperature changes on the accuracy of these measurements.
The NI CSM-200mA and NI CSM-10A current shunts have excellent temperature coefficients of resistance. Refer to the NI Products Web site for more information on the NI CSM-200mA and NI CSM-10A current shunts.
Check if the burden voltage can affect your measurement. Refer to Burden Voltage for an example on how to calculate the error due to burden voltage.
In applications where more than one current needs to be measured using the same DMM and the conditions require that the current cannot be interrupted across the load, use one of these two methods to measure the current:
- Use a break-before-make switch in multiplexer topology and place external shunts across the channels. Connect the shunts in series with the circuit under test and then measure the voltage drop across the shunts.
- Use make-before-break switches.
If the conditions allow interrupting the current flow through the circuit under test, it is still recommended to use external shunts. Switching currents above 1 A electromechanically can diminish the life of any switch. Refer to Switching Current for more recommendations for systems with switches.