Measurement system: A group of elements forming a system to carry out the act of measurement is called measurement system.
General elements of a measurement system: Generally a measurement system comprises of these basic elements. They are;
a. Sensor/Transducer b. Signal conditioner c. Display or readout device
In addition to this electrical power supply depending on the system. Fig. 1.1 shows a block diagram of a generalised measurement system and its elements.
Functions of elements of a measurement system
Transducer: Transducer is an element or a device which converts or transforms or transduces
the measurand into some other form generally electrical form. Fig. 1.3 gives basic concept of
transducer.
In the measurement of temperature using a thermocouple, the input to the thermocouple is heat, which the thermocouple transforms in to an em/proportional to the heat. Here thermocouple is a transducer.
Similarly in the measurement of pressure of a fluid using Bourdon pressure gauge, the input is pressure and the bourdon tube is a transducer, which gets displaced. This displacement being proportional to the pressure is displayed on the gauge.
Signal conditioner: A device connected next to the transducer or which receives the output signals of the transducer and converts it into suitable, usable, measurable level of signals. In the case of measurement of temperature using a thermocouple the output of the thermocouple is an electrical quantity of magnitude of say some milli-volts and to display or use this further it has to be amplified to the required level using an amplifier. Here amplifier is a signal conditioner.
Signal conditioner can vary from a simple network of resistance or network of matching impendence to complex multistage amplifiers with detectors, demodulators and filters. Signal conditioners are also termed as signal modifiers or signal processors. The output of the signal conditioner may be either analog or digital quantity.
Display unit: This unit displays the output of the signal conditioner and this display will be the quantitative form of the measurand. Display unit may be either of analog type (the simplest from being a panel meter with a pointer moving across a calibrated scale) or of a digital type. With the development of Computer technology analog signals are invariably
converted into digital form with the help of analog digital converter (ADC) and the measured quantities are displayed in derived units / engineering units on a digital panel. Fig. 1.4 shows the principle of measurement system and digital display.