Implementing Control with a Backup Function

Load devices are sometimes used when evaluating (measuring) DUT performance. Depending on the parameter being evaluated, multiple controllers can be employed to control the performance of the load device, but there are also times when the load device uses only one actuator. Such cases call for wiring of a system with a switched input mechanism to the actuator.

The following is an example in which control output from 2 controllers is switched as needed, and intake control is performed by a single actuator.

 

Overview

• The first controller performs temperature control using the temperature of the water from the DUT as a criterion.
• The second controller performs heating control using the energy consumed in the load device as a criterion.
• These controllers are separate, but the actuator at the load device is the same.

By using the control mode with backup function that comes standard with the UT55A UTAdvanced Digital Indicating Controller, we can switch 2 outputs as necessary and rely on only one actuator for the intake control. Control output computed from temperature control is input to the UT55A (controller 2) and output as-is for control of the actuator. The control output signal to the actuator computed from heating control is output on a circuit switched by the contact input to the UT55A.

Heating control by the UT55A requires the acquisition of heat as measured values. Because it can acquire up to 4 points of analog input (direct input of temperature takes up to 2 points), the UT55A inputs the temperature of the water that passed through the DUT (A), and the temperature of the water that passed through the heat exchanger (B). It combines these temperature values with flow values and performs calculations using a UT55A ladder program such as the following.

【Ladder Program Calculation Example】

PV = (B - A) × flow × constant

A: Water temperature from DUT (A)
B: Water temperature from heat exchanger (B)
Flow: Flow value of water passing the heat exchanger
Constant: Correction value for calculation