Process Scanner and Temperature Calibrator
Temperature Measurement and Control
These are documents and circuits which will help
learn Basic Temperature closed loop control, There
are many ways to control temperature.
System for Industrial Controls
- ON-OFF Hysteresis or Dead Band Control.
- Proportional Control with Reset.
- Full PID Control, Manual and Auto Tune.
The first one is an electronic emulation of
Thermostat or Electro-Mechanical Controls. The
second is Time Proportional like a slow PWM. The
third is the complete adaptive control.
While the first is like a limit switch, the
second works like a SMPS, the third PID takes into
account the speed of the process and dynamic
changes or disturbances of the system and
compensates in real time.
Example - In a Oven, one batch may have 100 metal
boxes to heat, the second batch may have 10 boxes,
the door may be frequently opened and the mains
power (heater) may be fluctuating. A system that
is able to adapt to these changes, without much
readjustments is the objective of an ideal process
control. The Accuracy and the Energy efficiency
being the most important.
Multizone Process Scanner
This could take current or voltage inputs from many
remote transmitters, 4-20mA or 0-1 V Inputs. Then it
would display the calibrated value in a LED display.
The Zone number was a digital display. This serves
as a monitor of process values. It had a analog
output with a digital channel byte-word output for
interface with other instruments.
This uses the CD4051-52 for the analog switching.
Operating this at +/- 7.5V gives best isolation from
channels and low ON resistance. Now you have many
types of devices to do this.
When a large area or object has to be heated, many
heaters are used. This device can monitor and
display the temperature at various points. The
Operator then can make adjustments in heating or
cooling so that he can maintain Uniform temperature
or a Temperature Gradient as specified by the
Control Education - Instrumentation
There are many ways, these scanners are used. Many
different parameters like pressure, temperature,
level are measured with different sensors and
converted to a 4-20 mA level using transmitters for
each sensor. Then many parameters can be measured in
one equipment, when it needs only periodic
attention. As the scan rate can be set from 1 to 50
seconds, the operator will be able to keep a tab on
the values or record it. This reduces the real
estate required on the control panel. Then the
control room can be small, as it has to be at a
vantage point, with a birds view of the entire
Temperature Calibrator for RTD and Thermocouple
This is a Milli-Volt and Milli-Amp Source for
Calibration of Temperature Measurement and Control
Instruments using Thermocouples. There is also a
Passive Variable Resistance Source for Simulating
a PT-100 RTD Sensor.
This calibrator was a simple solution i built.
This instrument itself was calibrated by
Instruments like the Calibrators
from Omega which are the best you can get.