how to calibrate temprature switch and flow switch ?



how to calibrate temprature switch and flow switch ?..

Answer / carl_ellis

The key to 'calibrating' a temperature switch is it is a
switch, it is not a continuous analog sensor. So there's
no need to mess around with a zero and span value, like you
would on temperature transmitter.

All that matters is setting the switch's trip point, the
setpoint, and in some cases, the reset
(deadband/hysteresis) point. There is no need to mess
around anything but the trip point, it's time consuming
enough to get a precise setpoint on switch.

You need to know
- the setpoint
- in some cases, the reset (deadband/hysteresis) point
values
- whether the setpoint (SP) is for a rising or falling
temperature. Because they're mechanical switches, a SP for
falling is NOT same as a SP for rising.
- switch functionality - Does the switch close or open on
rise or fall. There are applications for all the
variations: close on rise, close on fall, open on rise,
open on fall.

Check how to change the setpoint on the switch. Some
switches have a setpoint lock (nut). Some are blind
adjustments, some are adjustments with indicated
temperature values. Some have a separate
deadband/hysteresis adjustment. The latest temperature
switches are digital, and the setpoint and hysteresis reset
point are entered as values.

Many procedures require an actual test with a calibrating
heat/cold (dry block calibrator or oil bath) source and a
temperature "standard" is needed for a reference
temperature, to prove the mechanical setting is correct.
Sometimes the standard is a certified dry block with a
readout, sometimes it's a mercury thermometer, sometimes
its certified RTD with a certified readout. Older cal
equipment has stand-alone electrical equipment, like an
indicator lamp or an ohmmeter that is used to indicate
switch closure on the temp switch, more modern cal
equipment has built-in connections and an indicator for
that.

Make the setpoint adjustment, run the temperature source,
heat or cool, and note the trip and reset points. If
needed, make adjustments and re-run the test until the
setpoint (and reset point) are within the spec needed.

Record the results, put a cal sticker or tag on the beast,
and you're on to the next one.

Tell 'em Carl sent you.

Is This Answer Correct ?    8 Yes 1 No

Post New Answer

More Instrumentation Interview Questions

how can check the loopchecking for valves?

3 Answers  


which is the best type to measure level of a Tank(water). Displacer or Differential Pressure method?

2 Answers  


what is dc moter.

0 Answers   Jindal Steel and Power, Lupin,


What is mean by SMART in an Instrumentation. is any full form for SMART?

3 Answers  


how do we commission inergen system?

0 Answers  






What is seismic transducer?Where it is used?

1 Answers  


what are the difference between conventional and smart transmitter.

1 Answers  


any one suggest me how to calculate percentage of air leakage with formula,

0 Answers   SSL,


how to know power plant process with corresbonding laws&thoeries

1 Answers   Bhel,


What is the difference in clamp on type and inline type ultrasonic flow transmitter.

1 Answers  


What is the Difference between PE,IE and ISE

2 Answers  


i want the equation of this question. Tranmitter range is 120 mmwc and dcs flow range is 1700 nm3/hr. if i want to change dcs range from 1700 to 2400 nm3/hr then how much dp i have to enter in transmitter

2 Answers   GMR,


Categories
  • Civil Engineering Interview Questions Civil Engineering (5084)
  • Mechanical Engineering Interview Questions Mechanical Engineering (4451)
  • Electrical Engineering Interview Questions Electrical Engineering (16631)
  • Electronics Communications Interview Questions Electronics Communications (3918)
  • Chemical Engineering Interview Questions Chemical Engineering (1094)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (239)
  • Bio Engineering Interview Questions Bio Engineering (96)
  • Metallurgy Interview Questions Metallurgy (361)
  • Industrial Engineering Interview Questions Industrial Engineering (259)
  • Instrumentation Interview Questions Instrumentation (3014)
  • Automobile Engineering Interview Questions Automobile Engineering (332)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (97)
  • Marine Engineering Interview Questions Marine Engineering (124)
  • Power Plant Engineering Interview Questions Power Plant Engineering (172)
  • Textile Engineering Interview Questions Textile Engineering (575)
  • Production Engineering Interview Questions Production Engineering (25)
  • Satellite Systems Engineering Interview Questions Satellite Systems Engineering (106)
  • Engineering AllOther Interview Questions Engineering AllOther (1379)