difference between null and deflecting instrument.
- 5 Answers
- 55382 Views
- ONGC, I also Faced
- E-Mail Answers
Answer Posted / jasmine
The pressure gauge is a good example of a deflection-type instrument, where the value of the quantity being measured is displayed in terms of the amount of movement of a pointer. An alternative type of pressure gauge is the dead-weight gauge which is a null-type instrument. Here, weights are put on top of the piston until the downward force balances the fluid pressure. Weights are added until the piston reaches a datum level, known as the null point. Pressure measurement is made in terms of the value of the weights needed to reach this null position.
The accuracy of these two instruments depends on different things. For the first one it depends on the linearity and calibration of the spring, whilst for the second it relies on the calibration of the weights. As calibration of weights is much easier than careful choice and calibration of a linear-characteristic spring, this means that the second type of instrument will normally be the more accurate. This is in accordance with the general rule that null-type instruments are more accurate than deflection types.
In terms of usage, the deflection-type instrument is clearly more convenient. It is far simpler to read the position of a pointer against a scale than to add and subtract weights until a null point is reached. A deflection-type instrument is therefore the one that would normally be used in the workplace. However, for calibration duties, the null-type instrument is preferable because of its superior accuracy. The extra effort required to use such an instrument is perfectly acceptable in this case because of the infrequent nature of calibration operations.
| Is This Answer Correct ? | 20 Yes | 14 No |
Post New Answer View All Answers
IN CONTROL VALVE SPECIFICATIONS GENERALLY TERM " DE- 200" ."DM -400"USED,, WHAT IS DE/ DM STANDS FOR?
Positioner usage.
what is KV and XV valve
Describe how to use megger to measure the earth resistance and insulation resistance
Tell me the field calibration procedure step by step with diagram of pressure gauge, pressure switch, pressure transmitter, temperature switch, level switch, flow switch, flow transmitter.
flow transmeter accuracy 0.075% of full scale & find ucertainty is 0.025 % so what is maximum limit band of uncertainty
What is ultrasonic flowmeter?
i want to know the interview format fot gail, instrumentation. pls answer me in habib.sami1003@gmail.com
why we use cascade control and feed foreword control in 3 element control of boiler drum ?what is feed forward and cascade control system ?
Type of level transmitter commnly used in Procees area are the following. a.________________This type of level transmitter works as follows
1.what is the power consumption of three element drum level control in sugar industries? 2.how to reduce that?
How we connect a instrument with ground, Give brief explanation with help of diagram?
how to measure oxygen which methods are using?
How to calibrate capillary type level transmitter
send me HPCL paper
