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5
PRT Care and Handling Guidelines
5.1
PRT Care
CAUTION: READ THIS SECTION BEFORE REMOVING THE PRT
FROM THE SHIPPING BOX OR CASE
The 5624 Platinum Resistance Thermometer (PRT) is a delicate instrument.
Care must be taken in handling the PRT to maintain calibration accuracy. The
stress free design of the PRT sensor reduces the effects of mechanical shock. In
addition, contamination problems of the sensor at high temperature have been
eliminated. However, care should still be used when handling the PRT even
though the Alumina sheath is durable and provides good protection for the sen-
sor. Correct handling of the PRT will prolong the life expectancy. When not in
use, the PRT should be stored in the protective case provided by Hart.
The handle is not designed to be immersed. The temperature limits of the han-
dle are: –20°C to 200°C. Temperatures outside these limits can damage the
sealed portion of the handle and the connectors.
5.2
PRT Handling Guidelines
• Ideally DO NOT remove the probe directly to room temperature above
600°C. Slowly cool the PRT roughly at 150°C/hour above 600°C before
removing to room temperature. The PRT can be safely removed from an
instrument at 600°C or less and cooled to room temperature without con-
cern for the cooling rate. If the PRT is removed from instrument above
600°C, place the PRT in an annealing furnace for one hour.
• DO anneal the thermometer after shipment. Shipping the thermometer
can cause mechanical shocks that effect the accuracy of the thermometer.
Therefore, if possible, we advise that the thermometer be annealed before
use. The thermometer should be annealed at 965°C for four (4) hours.
• DO keep the thermometer as clean as possible. Always remove any fluid
or other debris from the sheath immediately after taking the thermometer
from a bath or furnace.
• For sheath longevity, insert the PRT at 500°C and ramp to higher temper-
atures.
• DO immerse the thermometer in the appropriate liquid for the tempera-
ture range. If a dry block is used, the well diameter should allow the PRT
to comfortably slip in and out without excess movement. For best results,
immerse the thermometer as deep as possible to avoid "stem effect" (the
temperature error caused by the conduction of heat away from the sen-
sor). Do not submerge the handle.
• DO allow sufficient time for the thermometer to stabilize before making
measurements. This allows for the best accuracy.
5 PRT Care and Handling Guidelines
PRT Care
15
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