A measuring system consists of
Right Answer is:
All of these
A measuring system exists to provide information about the physical value of some variable being measured. In simple cases, the system can consist of only a single unit that gives an output reading or signal according to the magnitude of the unknown variable applied to it. However, in more complex measurement situations, a measuring system consists of several separate elements as shown in Figure.
The measurement sensor includes
- Primary Sensors
- Variable conversion elements
- Signal processing
- Signal recording
Primary Sensors:- The first element in any measuring system is the primary sensor: this gives an output that is a function of the measurand (the input applied to it). Some examples of primary sensors are a liquid-in-glass thermometer, a thermocouple, and a strain gauge. In the case of the mercury-in-glass thermometer, the output reading is given in terms of the level of the mercury, and so this particular primary sensor is also a complete measurement system in itself. However, in general, the primary sensor is only part of a measurement system.
Variable conversion elements:- They are needed where the output variable of a primary transducer is in an inconvenient form and has to be converted to a more convenient form. For instance, the displacement-measuring strain gauge has an output in the form of varying resistance. The resistance change cannot be easily measured and so it is converted to a change in voltage by a bridge circuit, which is a typical example of a variable conversion element. In some cases, the primary sensor and variable conversion element are combined, and the combination is known as a transducer.
Signal processing elements:- Signal processing elements exist to improve the quality of the output of a measurement system in some way. It is important that the measurement system is designed properly such that the output from measurement sensors is of an appropriate amplitude and is as free from noise contamination as possible. The electronic amplifier is a very common type of signal processing element. This is used to amplify low-amplitude outputs from the primary transducer or variable conversion element, thus improving the sensitivity and resolution of the measurement.
For example, amplification is needed for thermocouples, which have a typical output of only a few millivolts. Other types of signal processing element are those that filter out induced noise and remove mean levels, etc. In some devices, signal processing is incorporated into a transducer, which is then known as a transmitter.