Transducers are the backbone of instrumentation and measurements. Physical phenomenon are utilized to convey quantities in terms of current and voltage. They are divided into two main categories: active and passive sensors. The former does not require any form of supply to convey a signal representing a quantity. Conversely, the latter necessitates electrical energy through a supply. The ones selected for the flow and temperature of water are passive meaning that they require 3 wire – two for the power and one for the signal. Thus, active sensors would need only 2 wires. The standard color codes hold for these applications – red for positive rail supply, black for ground reference and white for the actuating signal.
Adjacent is the picture portraying the water temperature sensor. A voltage will be produce directly proportional to the temperature. The supplied voltage will heat a winding, which will produce a voltage via a thermocouple, the heat produces the voltage potential difference. The principle of operation is very similar to that of a lambda/oxygen sensor located on every modern internal combustion engine. In such a situation the temperature of the exhaust gasses can be utilized as feedback in controlling the air fuel mixture.
Units of energy for the heating of water require the measurement for the flow of water. One can find numerous types of sensors utilization different technologies to measure this quantity. Most of them measure the static and dynamic pressure to come up with the flow of water for a given tubing diameter. As one can notice the module is passive, requiring a third supply wire (red).
