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 Process.
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.
Industrial Process Control Circuits