INSTRUMENTS

Installation, Operating, and Maintenance Instructions
Thermocouple and RTD Assemblies
p.1

Thermowell Use
The use of a thermowell is recommended for any pressurized application. Thethermowell prevents damage to the sensor element, and also allows removal of theelement without spilling process fluid.
Install thermowell into the process so a tight, non-leaking fit is achieved.
Coat the sensor element stem with a suitable heat transfer compound (e.g. A mixture ofgraphite and glycerin or petrolatum). Heat transfer compound is available.
NOTE: Above 350°F, some smoking of the heat transfer compound may occur
as the liquid portion of the compound vaporizes, leaving dry graphite to perform the heattransfer function.
After coating the element stem, install the sensor element. The pipe threads on theelement do not have to be sealed.

Thermocouple Instructions
Installation
1. Insert thermocouple into the thermowell. When inserting a spring-loaded stem,
positive contact with the bottom of the well will be achieved. Make sure wires inconnection head do not twist during insertion. If wires start to twist, disconnect thewires from the terminals and re-connect after screwing sensor into the thermowell.
2. Thermocouple wire of the same type as the sensor must be used to hook thethermocouple up to its instrumentation. Make sure the wire ends are clean andprovide good electrical contact with the terminals.
3. When hooking up the extension wire, match up wires so the same colors areconnected. (Thermocouple wire is color coded – the negative leg is always red, andthe positive leg varies, e.g. type K = yellow; J= white; E = purple; T = blue)
4. Install the thermocouple and extension wire at least one foot away from AC powerlines for best results. Do not run thermocouple wires in conduit with other wires.
5. The thermocouple connection head should not exceed 400 deg. F, and best results
are obtained when the head is as near as possible to room temperature.
6. Insertion: Proper insertion depth insures best accuracy. For best results,minimum insertion of ten times the stem diameter into the process is recommended.
Maintenance
1. Calibration frequency: Thermocouple calibration will gradually deteriorate at a ratethat varies with different applications. The frequency of calibration must be
determined in each case by the user.
2. Calibration is achieved by comparing thermocouple output with a working standard.
It is preferred to calibrate the thermocouple in its installed position. If the sensor isremoved for calibration, the thermocouple should be returned to the same locationand immersion depth for greatest reliability.
3. Periodically check the thermowell surface and the sensor sheath for corrosion ordamage. If damage has occurred, replacement may be considered.
4. Moisture can cause corrosion and decalibration in some thermocouple wire (forinstance, the positive leg of a J thermocouple is iron, and will readily rust). Take care
to prevent moisture buildup at thermocouple wire terminals.

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Installation, Operating, and Maintenance Instructions
Thermocouple and RTD Assemblies
p.2

INSTRUMENTS

RTD Instructions

Installation
1.

2.

3.

Insert sensor into the thermowell. When inserting a spring-loaded stem, positive
contact with the bottom of the well will be achieved. Make sure wires in theconnection head do not twist during insertion. If wires start to twist, disconnect thewires from the terminals and re-connect after screwing assembly into thethermowell.
Hook up RTD with clean copper wire. To ensure good calibration, all hookup wires
should be the same gauge and the same length. Connect wires at terminals inconnection head. The two sides of the RTD will have different color wires; samecolor wires are common legs.
Insertion: Proper insertion depth insures best accuracy. For best results, minimum
insertion of ten times the stem diameter into the process is recommended.

Maintenance
1. Calibration frequency depends on a variety of factors including temperature cycling,vibration, and shock. The frequency of calibration must be determined in each caseby the user.
2. Calibration is achieved by comparing RTD resistance with a working standard. It ispreferred to calibrate the RTD in its installed position. If the sensor is removed forcalibration, it should be returned to the same location and immersion depth for
greatest reliability.
3. Periodically check the sensor sheath or the thermowell surface for corrosion ordamage. If damage has occurred, replacement may be considered.

RTD Wiring Connections
Two-Wire: Provides one connection to each end of the element. This construction is suitable
where the resistance of the lead wire may be considered as an additive constant in the circuit,and particularly where the changes in lead resistance due to ambient temperature changes may
be ignored. Two-wire RTD instrumentation is very rare and mostly obsolete.
Three-Wire: Provides one connection to one end of the element and two to the other endof the element. Connected to an instrument designed to accept three wire input, sufficientcompensation is usually achieved for leadwire resistance and temperature change in leadwire
resistance. This is the most commonly used configuration.
Four-Wire: Provides two connections to each end of the element to completely compensate forleadwire resistance and temperature change in leadwire. Connected to an instrument designed toaccept four-wire input, this configuration is used where highly accurate temperature measurement is vital.
2 WIRE SINGLE

3 WIRE SINGLE

RED
WHITE

4 WIRE SINGLE

WHITE

2 WIRE DUAL

3 WIRE DUAL

4 WIRE DUAL

WHITE

RED
WHITE

WHITE

WHITE

WHITE

WHITE
BLACK

WHITE

WHITE
WHITE

RED
RED

RED
RED
RED

RED

RED
RED
BLACK

RED

RED
RED

RED
RED

WHITE
RED
RED
RED

TCRTDINST.0310 p.2

1.888.610.7664

151020030

525

www.calcert.com

REDsales@calcert.com