Instrumentation: Performing FAT Test

In our previous post on instrumentation, we looked at the analogue signal to and from instruments. What we need to do now is to have a look at how you would perform the Factory Acceptance Testing of these instruments you have installed

Before we go on, just a reminder to those who have not looked at the Manual for Electricians Volume 1, head to to get your copy


To start off, you need to set the engineering values on the instruments. Assume you have set up a differential pressure unit. You need to have the correct software and modem from the supplier to log onto the device and set up your parameters. Once this is done, you can proceed to testing the signal from the unit at 4, 8, 12, 16 and 20mA. These values need to display as per your setting of the parameters. You may have set the parameter to be 0 to 5m in the case of reading the level. This means you need to obtain the correct reading at each of these signal values. Should your values not be correct, you need to calibrate the device. Once calibrated, repeat the test and sign off on the FAT Test Report

This method remains the same even in the case of a modulating valve. You will provide a signal to the valve and you need to have the return signal match the percentage the valve has opened. The reason we do these tests is to ensure you have record of the operation and you will include these reports in the handover documentation you provide to your client at completion of the works

You will need to have an Analogue Current Loop Simulator and tester to perform these tests. These units vary in price and you may need to shop around to find a suitable unit. I have noticed a nice compact unit at that seems to be very easy to operate. Please note that it is entirely your choice which unit you buy and I am not going to endorse any specific brand.

Hope this helps and until next time, stay safe and please never work on live equipment! Follow the correct Lock Out Tag Out procedures at all times

1 thought on “Instrumentation: Performing FAT Test”

Comments are closed.