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
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 factory floor.
Process Control Circuits