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Proportional Process Controller Specifications

Front Panel Controls

Unlike a On Off temperature controller that works like a Thermostat. A Proportional controller turns on for a duration proportional to the heating required to ramp up the process.

Thermostat with digital display for PTC1000

If the set value and process value have a large difference the On period may be 90%. When the process value is close to set value, the on period is like 10%.

            Controller - Front

The on off cycle time is 10 seconds for electromagnetic relays. it could be 1 second for SSR. It could reduce further for mosfet switching. This is similar to PWM.

Display - Process Value PV

This is a 3 1/2 digit display which shows the process value from 000 to 1999 as chosen by user it could be deg C, Kg/cm2 or Lts/hr.

Push Switch - Displays Setpoint

This is a push switch which when pressed, makes Display  read SetPoint as required by user to control his process.

On-Output Status

LED Indicates Relay ON or OFF in Relay and Pulse Output Units. Units with 0-10V or 4-20mA, Output LED  is always OFF.

Vary SetPoint SP

This is an endless 10 Turn Potentiometer this is used to adjust SetPoint (SP) in tandem with Push Switch. Turning Clockwise it Increments SP till max. value, then turn anticlockwise to bring SP to Zero. Use a Plastic Screwdriver or Trimmer.(Tester).

Basic Operation

Press Push Switch to make Display read SetPoint (SP), this is the user defined point at which process is controlled. Now holding Push Switch pressed, adjust SP Pot to change Set Point to required value, use a small screwdriver.

Back Panel Termination

INPUT : 4 to 20 mA, Fused, Polarity is Important. From Sensor, DC Current.

          Controller - Back

OUTPUT : 4 to 20 mA, Polarity is Important. To Output Device or Actuator, which by using DC Current, drives 0% 4mA, 50% 12mA and 100% 20mA in Linear fashion.

SUPPLY : 230V 50Hz - L, N, E. Connect Proper Earth.

BAND : This is a Single Turn Potentiometer (300 deg) it sets the
Proportional Band of Control. Wide and Narrow are the ends of pot.

RESET : This is a Ten Turn Potentiometer (endless) it sets the
Integral or Reset or Error Cal.  Inc. PV  and Dec. PV are the  two ends of pot.

Electrical Precautions -



4 to 20mA, 4mA Displays 0% of Process Value 000 & 20mA Displays 100% of Process Value. This is to be specified by user as ... an example 750 Lts/hr.

Input @ 20 Ohms Shunt in STC1000PFC. Protection - Internal fuse of 2A and Semiconductor Protection Circuits to
safeguard from high energy circuits.

Environmental Limitations :
Cleaning and Maintenance : No Maintenance required, Clean front panel with moist sponge & Mild Detergent.

Power Supply : 230V AC 50Hz +/- 10%, Sine wave UPS & DG Sets.

Feedback and Temperature Control

Proportional Temperature Controller

A Temperature controller made with above process controller has the following changes in specs.

On-Output Status

LED Indicates SSR ON or OFF. Pulse Output goes High Max 15V or Low 0V. High Pulse turns on SSR. and this is Indicated by LED turning ON.

Display - Process Value PV

This is a 3 1/2 digit display which shows the Temperature value in Deg. Centigrade


INPUT : Thermocouple, Polarity is Important.

OUTPUT : DC Pulse Polarity is Important. To SSR. Pulse Maximum Voltage 12V DC at a Load of 250 Ohms.

Read More here - Analog Process Control Circuits

Back to Process Control Instrumentation






delabs Technologies

30th Aug 2020


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