RH CGS-240, Руководство пользователя

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Subsystems
CGS-240 Manual 6/15/2021
Page 55 of 148
on command input from any of the RS-232 ports. Supervisory operation such as set points (RH, dew point,
flowrate, etc.) are transmitted to the controller board via the touch monitor and PC. The job of the ECB is to accept
these set points, continuously measure the various analog and digital sensors, and control the various electro-
mechanical actuators in order to bring about and maintain the desired set point conditions.
Instrument specific configuration and calibration information, such as sensor coefficients, may also be written and
read via any of the three RS-
232 ports and resides within the ECB’s Electrically Erasable Read Only Memory
(EEPROM). All coefficients and other parameters are available via the touch monitor.
Voltage regulators on the ECB take the 24VDC input power and generate local +12VDC, +5VDC, and +3.3VDC
needed for various components on and off the board. DC power for sensors, relays, pumps, and others are
supplied directly from the ECB.
6.1.3 PRECISION TEMPERATURE MEASUREMENT BOARD, PT12
A Precision Temperature Measurement Board containing a multi-channel, 24-bit, analog-to-digital converter
measures all temperature sensors. Two of the channels are dedicated to system reference resistors. In addition to
the reference resistors, the following temperature probes are measured:
Tp Presaturator Temperature
Ts Saturation Temperature
Tc Chamber Temperature
Tcl Chamber Fluid Temperature
Tev Expansion Valve Temperature
Tr Refrigeration Compressor Temperature
Tpu Access Port Upper Temperature
Tpc Access Port Center Temperature
Tpl Access Port Lower Temperature
All temperature sensors in the humidity generator are
100
Ω Platinum Resistance Thermometers (PRT’s).
The board measures all thermometers using full current reversal DC pulse mode excitation. It ratio-metrically
compares these raw probe measurements to measurements of the precision reference resistors to determine their
precise resistance values.
The resistance values are then computed into individual temperatures using each probe’s specific coefficients. The
results are provided to the ECB via an RS-232 connection on UART7. The Precision Resistance Measurement Board
requires 12 VDC which is supplied from the AD3 port of the ECB.
Figure 6.4