54 cHAPTER 4: Operation
Model 336 Temperature Controller
4.4.6 Thermocouple
Sensor Input Setup
(Model 3060 Only)
When a Model 3060 Thermocouple option is installed in the Model 336, a setting of
Thermocouple becomes available under the Sensor Type parameter in the Input
Setup menu. The standard diode/RTD sensor inputs can still be used when the Ther-
mocouple option is installed, but the Thermocouple and standard inputs cannot be
used simultaneously. Refer to section 7.6.1 to install the Model 3060.
Thermocouples include a variety of commercial (such as E, K, T) and specialty types
such as cryogenic (Chromel–AuFe). Standard curves are included in the Model 336 for
the types listed in TABLE 4-7. Other types can be used as long as an appropriate tem-
perature response curve is loaded as a user curve. Representative thermocouple spec-
ifications are given in TABLE 1-2. The Model 336 provides one thermocouple range
and no excitation because thermocouples do not require it. Internal room tempera-
ture compensation is included for convenience (section 4.4.6.2) and should be cali-
brated before use. Room temperature compensation is enabled by default, but can be
turned off if external compensation is being used.
Menu Navigation:
Input SetupQInput (C or D)QSensor TypeQThermocouple
Interface Command: INTYPE
4.4.6.1 Internal Room Temperature Compensation
Room-temperature compensation is required to give accurate temperature measure-
ments with thermocouple sensors. It corrects for the temperature difference
between the instrument thermal block and the curve normalization temperature of
0 °C. An external ice bath is the most accurate form of compensation, but is often
inconvenient. The Model 336 has internal room-temperature compensation that is
adequate for most applications. You can turn internal compensation on or off. It oper-
ates with any thermocouple type that has an appropriate temperature response
curve loaded. Room-temperature compensation is not meaningful for sensor units
measurements.
Room temperature compensation should be calibrated as part of every installation
(section 4.4.6.2)
Menu Navigation:
Input SetupQInput (C or D)QRoom CompensationQ(Off or On)
Default: On
Interface Command: INTYPE
4.4.6.2 Internal Room Temperature Compensation Calibration Procedure
Factory calibration of the instrument is accurate to within approximately ±1 K. Differ-
ences in thermocouple wire and installation technique create errors greater than the
instrument errors. To achieve the best accuracy, calibrate with the thermocouple
actually being used, because it eliminates most sources of error. If that is not possible,
use a thermocouple made from the same wire.
It is best practice to use the same material for thermocouple wires; if it is at all possible, it
is also best to avoid splices. When splices are necessary, continue the splice with the same
type of material.
For less demanding applications, a short across the input terminals will suffice. Both
thermocouple inputs should be calibrated, even if they use the same type of thermo-
couple. An appropriate curve must be selected and room temperature compensation
must be turned on before calibration can be started.
Follow this procedure to calibrate room temperature compensation:
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