chapter  4
Sensors and Their Responses
Pages 32

A BEMS outstation is basically a microprocessor processing digital electrical signals. But most plant equipment controlled by a BEMS is controlled on temperature, pressure or flow, rarely on electrical signals. So these nonelectrical parameters must be measured and converted to electrical signals, invariably a voltage. This measurement and conversion is the function of the sensor, transmitter and transducer. The sensor responds to the change in the measured parameter (e.g. the temperature), the transducer changes the sensor signal to an electrical signal (e.g. a pressure into a voltage) and the transmitter is the electronic circuitry to enable a suitable strength voltage proportional to the sensed parameter to be sent to the outstation. Often the sensor transmitter and transducer are integral in a measuring device and it is difficult to separate them, so that sensors are commonly known as transducers.