National Instruments NI 9423 Getting Started Guide

NI 9421 Signals
Each channel of the NI 9421 has a DI terminal or pin to which
you can connect voltage or current signals. The NI 9421 also has
COM, a common terminal or pin that is internally connected to
the isolated ground reference of the module.
The NI 9421 has sinking inputs, meaning that when the external
device drives current or applies voltage to the DI terminal or pin,
DI provides a path to COM for the current or voltage. The
NI 9421 internally limits current signals connected to DI.
Connecting Sourcing-Output Devices
You can connect 2-, 3-, and 4-wire sourcing-output devices to the
NI 9421. A sourcing-output device drives current or applies
voltage to DI. An example of a sourcing-output device is an open
collector PNP.
Connect the output of the sourcing-output device to DI on the
NI 9421. Connect the common of the external device to the COM
terminal or pin.
NI 9421 Getting Started Guide | © National Instruments | 13

National Instruments NI 9423 Specifications

General

Brand	National Instruments
Model	NI 9423
Category	Measuring Instruments
Language	English