Test Automation

Using a PC or Laptop to control a test procedure greatly simplifies the operation and provides repeatability across multiple user operators. The Solid-State Relay Module can be used to make contact closures at the test apparatus and the Digital Input Module can be used to sense contact closures from the apparatus. The Analog Output Module can be used to inject a voltage to the apparatus and the Analog Input Module can be used to measure a voltage from it. All four of these DAQ Modules can be plugged end-to-end and hooked up to a single COM port of the host PC running ModCom.

A test application in ModCom will most likely consist of a Script which defines the various steps in the test procedure. This Script can be started with a Push Button on the screen, or started automatically at run-time by including it in the Initialization setup box. Below is an example of an application that will test the continuity of a cable harness using a Digital Input Module on one end and a Digital Output Module on the other.

Connect one end of the cable harness wires to the inputs of the Digital Input Module. Connect the other end of each wire to the corresponding output of the Digital Output Module. Write a Script that executes the following steps.

Step 1: Transmit a command to read the first channel of the Digital Input Module and send the response to a Text Window on the screen. This will be the state of the input channel when the opposite end of the cable harness wire is left open.

Step 2: Transmit a command to set the first channel of the Digital Output Module low. This will pull the cable harness wire to ground.

Step 3: Transmit a command to read the first channel of the Digital Input Module and send the response to a 2nd Text Window on the screen. This will be the state of the input channel when the opposite end of the cable harness wire is pulled to ground.

Step 4: Transmit a command to set the first channel of the Digital Output Module back to high so that it will be ready for the next test.

Repeat the above steps for each wire in the cable harness using a separate pair of Text Windows for each of the wires. Then write a Conditional statement for each of the wires that will look at it’s pair of Text Windows and verify that they show the expected response. If not, have it turn on a Signal Lamp on the screen to notify the operator of the failure. A separate lamp can be used for each wire being tested if desired.

Note: Each Text Window can be setup to show a default message. Typing in a default message equal to the expected response from the DAQ Module will prevent the Conditional from triggering prematurely before the test Script has started.

The Digital Input Module and Digital Output Module can test 8 wires at a time. However, up to 32 of these modules can be plugged end-to-end on the same serial cable allowing 256 individual wires to be tested at once. Be sure to set each DAQ Module to a different address using the DIP switch on the board.