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Pressure Measurement
The Calibrator can accept either the Fluke 700 or 6100 series pressure modules. Pressure
modules plug directly into the front panel Lemo connector. The Calibrator firmware
automatically detects the type and value of the module you are attaching, and recognizes
the following units of measurement:
•
PSI
(pounds per square inch)
•
inH2O4°C
(inches of water at 4 degrees Celsius)
•
inH2O20C
(inches of water at 20 degrees Celsius)
•
cmH2O4°C
(centimeters of water at 4 degrees Celsius)
•
cmH2O20C
(centimeters of water at 20 degrees Celsius)
•
BAR
(bars)
•
mBAR
(millibars)
•
KPAL
(kilopascals)
•
inHG 0°C
(inches of mercury at 0 degrees Celsius)
•
mmHG 0°C
(millimeters of mercury at 0 degrees
Celsius)
•
Kg/cm2
(kilograms per square centimeter)
Theory of Operation
The Calibrator serves as an accurate laboratory device for calibrating thermocouples,
RTDs, pressure devices, and low-level dc voltages and currents. The main PCB
assembly, and several subassemblies, work together to provide high-reliability and easy
maintenance.
Micro-Controller Section
The Atmel ATmega 103 micro-controller is the heart of the 525A. It contains all of the
program memory, nv-ram, FlashROM, static RAM, and EEProm. The micro-controller
allows a minimal amount of external glue logic. The main external digital ICs are the RS-
232 driver, relay drivers, LCD controller, and the digitally controlled analog switches.
Many of the ICs are interfaced through the micro-controller's three-wire SPI bus
minimizing interconnecting lines. Inputs or outputs begin with instructions entered
through the keypad or through remote communications (serial or IEEE-488) into the
micro-controller. The micro-controller processes the commands and sets conditions that
are appropriate for the command.
525A
Theory of Operation
11
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