NI-9217 Getting Started

Connecting the NI-9217

The NI-9217 provides connections for four RTD channels.

NI-9217 Block Diagram


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  • RTD channels share a common ground that is isolated from other modules in the system.
  • Each RTD channel is filtered and then sampled by a 24-bit analog-to-digital converter (ADC).

NI-9217 Pinout


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Table 1. Signal Descriptions
Signal Description
COM Common reference connection to isolated ground
EX Excitation source connection
RTD+ Positive resistance temperature detector connection
RTD- Negative resistance temperature detector connection

NI-9217 Connection Guidelines

  • Make sure that devices you connect to the NI-9217 are compatible with the module specifications.
  • You must use 2-wire ferrules to create a secure connection when connecting more than one wire to a single terminal on the NI-9217.
  • For the NI-9217 with push-in spring terminal, push the wire into the terminal when using a solid wire or a stranded wire with a ferrule.
  • For the NI-9217 with push-in spring terminal, open the terminal by pressing the push button when using stranded wire without a ferrule.

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-9217:

  • Use ferrules to terminate wires to the detachable connector.
  • Use the NI-9939 connector backshell kit.

Connecting 3-Wire and 4-Wire RTDs

You can connect any combination of 3-wire or 4-wire RTDs to the NI-9217. Each NI-9217 channel contains circuitry that automatically detects the type of RTD connected to the channel. The NI-9217 scans all four input channels and automatically configures each channel for the appropriate mode. In 4-wire mode, the EX terminal is a 1 mA current source. In 3-wire mode, the RTD+ terminal is a 1 mA current source. The NI-9217 compensates for the error that lead resistance causes in 3-wire mode.

If you are using a 4-wire RTD, connect EX to the positive lead of the RTD. If you are using a 3-wire RTD, do not connect the RTD to the EX terminal.

Figure 1. Connecting an RTD to the NI-9217

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For the best measurement results when using the NI-9217 with a 3-wire RTD, use equal-length wires between the RTD+ terminal and the RTD and between the COM terminal and the RTD. Also, keep the lead resistance within 5% of the nominal RTD value. The NI-9217 accuracy specifications account for this lead error.

Note The accessory used with the NI-9217 may introduce additional lead resistance mismatch error in 3-wire mode. Refer to the device specifications for information about errors due to lead resistance mismatch.