This is a generic or standard controller for any type of process. Shown here is a temperature controller.
The STC1000 could be used for Ovens or furnaces, liquid
baths, heating or environment chambers. It has a single analog
input and an analog or relay output.
Analog inputs could be like 4-20 mA, thermocouple or RTD.
Analog outputs can be 0-10 V for a thyristor drive, SSR drive
output or potential free contacts of a relay to operate
external 3 phase contacters.
The closed loop control could be On-Off or Time-Proportional. It was known as digital temperature indicating controller. Sometimes it would be used just as a Alarm or in a Trip circuit for protecting a system, when a uP or uC based PID controller fails.
This is used in the processing of plastics, rubber, metals and in chemical plants too. Here is a checklist that was made for helping its fabrication. You can see the limitations in which we manufactured these products. An optimum quality was evolved, defined by a user's affordability of the product.
In this controller you can see a sensor open indication. When the sensor breaks, the temperature controller may continue to turn on the actuators or heaters, It may even Oscillate. So when a high impedance is detected in the sensor input terminals, the output relay is shut off and a LED is turned on to simplify operator's diagnosis.
Mount the controller a distance away from heaters, ac-drives
and vibrating parts. Avoid direct sunlight on controller, fix
controller in a sealed control panel. Earth the point where
the thermocouple senses heat. Some heaters leak. The machine
has to be earthed.
30th Mar 2020
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