Here at REA Technologies,Inc., we are sometimes tasked to build test equipment in order to complete a repair.
Recently I was given an Powers Process Controls "535 Process Controller" used in the production of furniture. It was not certain whether the controller was at fault, or the problem was somewhere else in the machine. So a complete test of the 535 Process Controller was requested.
According to the machine prints supplied by the customer, One input labeled "DELIVERY" required a J-Type Thermal Couple input. I satisfied this input with a Thermal Couple we had in bench stock. Two other inputs were labeled +RSP/-RSP and +PLATTEN/-PLATTEN. These two inputs were 0 to 20mA inputs. To satisfy these two inputs, I designed and built a variable milli-amp source. The milli-amp source was controlled by a potentiometer, so that I could set the proper milli-amp current for the 535 Process Controller's inputs.
Without satisfying the three inputs, the 535 Process Controller would power up with RSP, PV1, and PV2 alarms. These alarms would stop the process controller from continuing and prevent further testing.
With the Thermal Couple and my milli-amp source, I was able to test all the Inputs as well as control the functions of the Outputs. The 535 Process Controller functioned normally. One of our field technicians went back with the unit and found the actual cause of the problem in the machine. He performed the necessary repairs and got the customer's machine running again.