DC and AC Current
The NI 4065 allows you to measure currents ranging from a few picoamps to three amperes. DC Current mode has four ranges that go from 10 mA to 3 A in decades, and AC Current mode has four ranges that go from 10 mArms to 3 Arms in decades.
Shunt Resistors
The NI 4065 uses internal shunt resistors with temperature coefficient and power ratings selected to reduce resistor self-heating errors. For the effect of temperature changes on the accuracy of the measurements, refer to Related Documentation for the NI 4065 specifications document and the temperature coefficient. Refer to the following table for the shunt resistor values.
| Range | Shunt Resistor Value |
|---|---|
| 3 A | 0.01 Ω |
| 1 A | 0.01 Ω |
| 100 mA | 4.8 Ω |
| 10 mA | 4.8 Ω |
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Tip The current measurement path within the NI 4065 utilizes an electromechanical relay that provides very low resistance to assure a low burden voltage. While this relay has an exceptionally long life, you can take special precautions to ensure reliable operation.
Whenever possible, switch the NI 4065 into the current measurement function before applying the current. Switching inductive current sources generally creates flyback voltages that stress the relay and, if done frequently, can shorten the reliability of the relay. Also, avoid interrupting the current by switching out of the current measurement function when currents are flowing through the circuit. |