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.

How can we use feedback signal frm rtd for monitoring and in dcs for controlling ,then which type of rtd is sutaible 2 , 3,4wire and why ?

0 Answers  

---

What the basic of communication?

4 Answers   Schneider,

---

difference between plc and dcs?

3 Answers   Honeywell,

---

What is stripper & spilitter ? Diffrence in this.?

0 Answers  

---

how to calculate MMWC values in to Tonns(MMWC values showing in DP transmitter and Tonns value showing in Totalizer). please tell me details?

2 Answers   Chemin C I, MSP,

---

what is temperature compensation?

1 Answers  

---

What is the full form of PMMC ?

7 Answers   DVC,

---

It is desired to reduce effect of 50Hz pick up in a thermocouple measurement. If a third order LP filter is used for this, what should be its cut off frequency, if gain should be 0.001 at 50Hz.

1 Answers   Honeywell,

---

what is field bus system. need defination

3 Answers   Takreer,

---

what is the difference between transmitter and smart transmitter ?

4 Answers   Aditya Birla,

---

Explain any simple temperature control system.

3 Answers   HGJ, L&T,

---

how to draw a flowchart for swapping two numbers using bit wise operators?

1 Answers  

---