PGC, Inc 500-1000 CFM Air Handler May 2006
Appendix A A-19
CALIBRATION
C
ALIBRATION, AIR/RH
The air temperature and Rh are measured by a self-contained and calibrated Rotronics
HygroClip™ T/Rh transmitter. The Rotronics HygroClip™ T/Rh transmitter should be
recalibrated annually. The three different options for calibration are Exchange, Calibration in an
Independent Chamber, and Calibration In Place
Exchange
Both PGC and Rotronics© (the sensor manufacturer) have a sensor exchange program. Contact
Rotronics© for details regarding their plan and calibration schedule. For a nominal calibration
fee, PGC will provide a calibrated temperature and Rh transmitter as often as you desire. The
replacement sensor will be shipped complete with calibration data that can be used for validation.
The returned sensor will be re-calibrated and used as an exchange sensor in the future. The “as
found” data from the returned sensor can be forwarded to the customer to be used for validation.
Contact PGC for current pricing for this service.
The customer can also purchase a second calibrated transmitter, which can be interchanged with
the original sensor. The original sensor can then be returned to Rotronics©, PGC, or a calibration
laboratory for re-certification. This process can then be repeated on a schedule determined by the
customer’s specific requirements.
Calibration in an independent chamber
The HygroClip can also be calibrated through the serial port of a Windows based PC. An
interface cable, available from Rotronics, allows the PC to communicate directly to the
HygroClip. The HygroClip is then positioned in a stable chamber, compared to a reference
standard, and adjustments made to the calibration constants from the PC. Contact Rotronics or
PGC for more details regarding PC based HygroClip calibration.
Calibration in place
Rotronics© produces a hand-held device, called a HygroPalm™, that can be used to calibrate the
HygroClip™ transmitter, without removing the transmitter from the air handler. A special cable,
available from PGC, is connected from the HygroPalm to the communication line in the conditioning
unit. The HygroPalm then interrupts the communications from the HygroClip™ to the PLC in order to
modify the calibration constants that are stored in the HygroClip™. The HygroPalm can be equipped
with a second, calibrated HygroClip™ that is used as a reference probe, or an independent reference,
supplied by the customer or the calibration technician, can be used as the reference.
The actual location of the connection for the HygroPalm™ depends on where the HygroClip™ is located.
If the HygroClip™ is located within 5 meters of the PLC in the electrical compartment on the air handler,
it does not require external amplification of the digital signal. In this case, the HygroClip™ can be
connected directly to the PLC. To calibrate a HygroClip™ connected directly to the PLC, the
HygroPalm™ interface cable should be connected to the DIO and common connections on the PLC pc
board. This connection can be “piggy-backed” onto the existing wires in these terminals, or a special
cable, available from PGC can be used to connect to a calibration header on the circuit board.
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