B875-111 Analog Input, Calibration

Calibration Tools

The analog input module is calibrated at the factory prior to shipment. To ensure the module’s accuracy, the trim-pot should be calibrated regularly on a yearly interval.

The following tools and materials are needed to calibrate an analog input module:

A precision digital readout voltmeter with an accuracy of 0.0001 V on a 10 V scale.

A 1/8-inch bit, thin-blade screwdriver.

A 1/4-inch Phillips-head screwdriver.

An adhesive (such as Loctite or Glyptol) to secure trim-pot adjustment screws.

Calibration Procedure

Use the following table to calibrate the module.

Step	Action
1	Remove two screws and label located on front-panel of analog input module to allow access to trim pot. Note: The trim pot adjusts the total magnitude of the range (full scale). Refer to trim-pot location diagram, below.
2	Open analog input module handle to expose connectors and terminals.
3	Connect digital voltmeter (DVM) minus lead to voltage reference - (terminal number 38) and plus lead to voltage reference + (terminal number 39). Refer to voltmeter connection diagram, below. Note: Field wiring may remain connected during calibration. Five minutes of warm-up is sufficient to attain temperature stability.
4	Adjust reference voltage trim pot for an indication of 4.500 V 0.0001 V.
5	Secure trim pot in place with adhesive.
6	Disconnect voltmeter, return connections to their pre-calibration state, close module handle. Replace front label removed in step 1, above.

Trim Pot Location Diagram

Trim pot location diagram.

Voltmeter Connection Diagram.

Voltmeter connection diagram.