Functional elements of an instrument
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The document outlines the key functional elements of an instrument: 1) The primary sensing element makes first contact with the measurand or variable being measured (e.g. a coil carrying current in an ammeter). 2) The variable conversion element converts the output of the primary sensing element into a form suitable for measurement (e.g. a magnet converting current into deflection in an ammeter). 3) The variable manipulation element adjusts the level of output if needed for further processing (e.g. a transformer increasing voltage level for adequate deflection in an ammeter).
Functional elements of an instrument
- 1. FUNCTIONAL ELEMENTS OF AN INSTRUMENT PREPARED BY; S.SANTHOSH KUMAR-EEE SNS COLLEGE OF ENGINEERING COIMBATORE 1
- 3. *The variable that you want to measure is mentioned here. *It is called as the "Measurand“. *For example, If you want to measure current, then current is the measurand.
- 4. PRIMARY SENSING ELEMENT:- The Primary Sensing Element, as shown in the block diagram. You can remember it better if i mention it as "First Sensing Element". Thats right. The Element (Part) of an instrument which makes first contact with the measurand is called the primary sensing element. For example, In Ammeter (which is used to measure current), the coil carrying the current to be measured is the primary sensing element.
- 5. VARIABLE CONVERSION ELEMENT:- The output of the Primary sensing element may not be suitable for the actual measurement system. For example, in ammeter, the output from the coil is current, so there we place a magnet to get a deflection due to the current passing in the coil. So here the magnet acts as a variable conversion element, converting current into physical movement which is the deflection and by measuring the amount of deflection we can measure the amount of current. Note:- Some instruments do not need this variable conversion elements, whereas some instruments need more than one. Also keep in mind, that the original information about the measurand must be retained during the process of such conversion.
- 6. VARIABLE MANIPULATION ELEMENT:- This is the tricky part. The level of the output from the Variable conversion element may not be enough for the next stage. For example, in case of ammeter if the amount of current to be measured is so small , it may not be enough to cause any deflection in the magnet. So here a transformer can be used to increase the voltage to get enough deflection. So in this case the transformer will be the Data Manipulation Element. Note:- The Variable conversion element and the variable manipulation element are together called as Data conditioning element since they help to obtain the signal in pure and acceptable form from highly distorted form.
- 7. DATA TRANSMISSION ELEMENT:- If the elements of the system are physically separated, it is necessary to transmit the data from one stage to the other. So we need this Data Transmission element. The data conditioning and the Data transmission are together called as the intermediate stage of an Instrument.
- 8. DATA DISPLAY ELEMENT:- So now the measuring is done and we need to present the data in a suitable form so that it is easily understood by the observer and for this the Data Presentation Element is used. In case of our Ammeter Example, it is the Pointer and the scale arrangement that acts as the Data presentation element. If the output data is to be monitored, a visual display can be used and if needs to be recorded then magnetic tapes , recorders or hard disk drives can be used. The Data Presenting Stage may be called as the Terminating stage of an instrument.