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4 Installation
4.1 Environmental Issues
Ideally, temperature calibration equipment should be used in a calibration
laboratory or other facility specifically designed for this purpose. Environ
-
mental requirements include:
•
Stable temperature and relative humidity <80%
•
Clean, draft-free area
•
Low noise level: low radio frequency, magnetic or electrical interfer
-
ence
•
Low vibration levels
4.2 Mounting
Most often temperature standards, primary and secondary, are used to cali-
brate other temperature-sensitive equipment. The PRT must be mounted
carefully to avoid any damage to the sheath or sensor. If the fluid bath used
does not have a lid designed for PRT insertion, clamps should be used to
ensurethehandleandcablearenotimmersed.Do not screw the clamps
too tight. Over tightening will damage the sheath. If metal comparison
blocks are used in the bath, maintain a close fit between the thermometer
sheath and the well in the comparison block. However, allow for the ther-
mal expansion of the thermometer sheath when determining block well
tolerances.
4.3 Lead Wire Identification
The 5626 and 5628 PRTs are equipped with a four-wire cable. The same
circuit schematic applies to both PRTs (see Figure 3). Four lead wires are
used to cancel lead wire resistance. For best results, the readout device
should be equipped to handle four-terminal resistors.
The lead wires are four different colors. Lead wire pairs attached to each
end of the sensor are identified by red and black heat shrink tubing.
4
Installation
9
BLACK
(Heat Shrink)
RED
(Heat Shrink)
Figure 3 PRT Schematic