Dielectric Absorption

NI Digital Multimeters Help (NI-DMM 18.1)

Edition Date: March 2018

Part Number: 370384V-01

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Dielectric absorption caused by cable materials can increase settling time. The figure below illustrates dielectric absorption due to cable resistance and dielectric polarization capacitance where:

RDA = Insulation resistance of cabling (10 GΩ–1014Ω)

CDA = Dielectric polarization capacitance (0.1–1 pF/ft)

CC = Cable capacitance (10–40 pF/ft)

The RC formed by RDA and CDA results in slow settle tails that significantly lengthen settling time.

The best way to avoid dielectric absorption effects is to use a high-quality cable, such as Belden 83317E available. Refer to the Belden CDT Incorporated Web site at www.belden.com for information about this cable.

NI recommends cables with Teflon, polypropylene, or polyethylene insulation. For more information about cabling requirements, refer to Interconnects and Cables.

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