Measurement Considerations

Refer to the following sections for considerations to take when making PXIe-4081 measurements.

Normal-Mode and Common-Mode Signals
A normal-mode signal is a signal applied differentially to the DMM front panel connectors for the purpose of measuring that signal.
Input Resistance
Resistance is a measure of the opposition to the flow of current. The input resistance of the DMM can affect the accuracy of voltage measurements, particularly when the resistance of the source voltage is comparable to the input resistance of the DMM.
Burden Voltage
Burden voltage is the voltage drop caused by current flowing through a current measuring device.
Performing Offset Nulling
Offset nulling consists of measuring the corresponding zero reading in a measurement path and subtracting this value from subsequent samples. The way you connect the leads to obtain the zero reading depends upon the type of measurement you are taking.
Thermal Voltages
Thermal voltages, also known as thermal EMFs, are voltages created by the junction of dissimilar metals when a temperature difference exists between these junctions. The generated voltage increases with temperature. The specific metal-to-metal junctions result in specific temperature coefficients (V/°C) called Seebeck coefficients.
Resistor Self-Heating
As dissipation of power in a resistor increases, the temperature of the resistor increases and causes a change in the resistance value. You can calculate how much error is introduced in your measurement by resistor self-heating from the derating curve of Rated Power(%) vs. Ambient Temperature and a resistor's temperature coefficient (tempco), information commonly given in a resistor specification.
Dielectric Absorption
Dielectric absorption caused by cable materials can increase settle time.

PXIe-4081 User Manual

PXIe, 7½-Digit, ±1,000 V, Onboard 1.8 MS/s Isolated Digitizer, PXI Digital Multimeter

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