Platinum
Resistance Thermometers
operate on the principle that the electrical resistance of a metal
conductor changes as a function of temperature. PRT's provide
an accurate, stable and repeatable means of absolute temperature
measurement. The accuracy of a PRT may be independent of the distances
between the sensor and the instrument whether it be an indicator,
recorder, controller, data logger or computer. Copper hook-up
wire is generally used between the sensor and instrument.
Marlin PRT
probes consist of a platinum resistance element that is encapsulated
and circuited in a mineral insulated, metal sheath construction
and terminated by means of bare wire, quick connectors or terminal
heads. This construction provides a rugged probe that is moisture,
pressure, shock and vibration resistant and also is bendable up
to the element area.
General
Selection Parameters
The conditions of measurement determine the type of PRT used.
Temperature, atmosphere, protection, response, and service life
should be considered. The following descriptions serve as a guide
to selection.
- The
Platinum Resistance Element
- Select
the PRT element that will be capable of operating in your application
range. The reference resistance (100 Ohms@0°C - typical) and
temperature coefficient (Alpha of 0.00385 - typical) must match
the instrumentation in your system.
- Tolerance
of the PRT Element
- A range
of limits of error elements are available (0.1% - typical).
In general the better the tolerance the more expensive the thermometer.
- Sheath
Alloy
- Select
a sheath alloy that will withstand the temperature and possible
corrosives of your application. A 316SS sheath is standard.
- Probe
Diameter
- Use the
probe diameter that will withstand the rigors of your application
but with minimal affect on it. Because the element can be broken
if the sheath is bent in the element area, it is recommended
that a minimum of 0.187" diameter thermometer be used. Smaller
diameters are available on request. (Please
consult the factory.)
- Process
Connections
- In order
to attach and/or seal the thermometer in your application you
can use a fitting - braze, weld or solder it in place.
- Terminal
and/or Extension Type
- For connection
to instruments various terminations and extensions are available.
Select the circuit that is required to match your instrumentation.
For
more information regarding Platinum Resistance Thermometers
Please Consult your Marlin Catalog, Pages C-3 to C-19.
If
you do not have a Marlin Catalog - Click
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