NI-9423 Getting Started

NI-9423 Nomenclature

In this article, the NI-9423 with screw terminal and NI-9423 with spring terminal are referred to inclusively as the NI-9423. The information in this document applies to all version of the NI-9423 unless otherwise specified.

NI-9423 Block Diagram

NI-9423 Pinout

Table 1. Signal Descriptions
Signal	Description
COM	Common reference connection to isolated ground
DI	Digital input signal connection
NC	No connection

LED Indicators

Each channel has an LED that indicates the state of the channel, as the following table describes. The LEDs are disabled when the chassis is in sleep mode.


LED Pattern	Indication
Solid	The channel has been programmed to be in the ON state.
Off	The channel has been programmed to be in the OFF state.

Connecting the NI-9423

The NI-9423 provides connections for eight digital input channels.

Note You must use 2-wire ferrules to create a secure connection when connecting more than one wire to a single terminal on the NI-9423.

NI-9423 Signals

Each channel of the NI-9423 has a DI terminal or pin to which you can connect voltage or current signals. The NI-9423 also has COM, a common terminal or pin that is internally connected to the isolated ground reference of the module.

The NI-9423 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-9423 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-9423. 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-9423. Connect the common of the external device to the COM terminal or pin.

The NI-9423 channel registers as ON when the sourcing-output device applies a voltage or drives a current that is in the input ON range to DI. The channel registers as OFF when the device applies a voltage or drives a current that is in the input OFF range to DI. If no device is connected to DI, the channel registers as OFF.

High-Vibration Application Connections

If your application is subject to high vibration, NI recommends that you follow these guidelines to protect connections to the NI-9423:

Use ferrules to terminate wires to the detachable connector.
Use the NI-9927 backshell kit with the NI-9423 with screw terminal or the NI-9981 backshell kit with the NI-9423 with spring terminal.