GE MOA 280i, Руководство по эксплуатации и обслуживанию

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GE Analytical Instruments ©2006 DLM 14291 Rev. A
1-8
•
PMT amplifier
•
Analog to digital converter (ADC) board
•
Microprocessor and Outputs board
•
Power supply board
•
24 V power supply
•
Front panel display
•
Keypad.
The PMT amplifier processes the signal from the PMT. To provide both high
sensitivity and wide dynamic range, the amplifier has two gain ranges. High Gain is
used for measurements requiring high sensitivity (liquid samples and exhaled
breath). The amplifier in high gain has a linear response up to ~1 ppm of NO gas or
~400 picomoles of NO
2
-
or NO
3
-
for liquid samples. The low gain decreases the
sensitivity of the amplifier, permitting measurement of up to ~500 ppm of NO gas
or ~200 nanomoles of NO
2
-
or NO
3
-
for liquid samples. The analog output signal (mV
only) is obtained from the amplifier. A switch on the amplifier sets the full-scale
voltage. When the switch is in the down position the output range is 0–1V. When
the switch is in th eup position, the output range is 0–10V.
The amplifier is also connected to the ADC board which also monitors three
pressure transducers (cell, supply and exhalation), the cooler thermocouple and
the thermal mass flowmeter. The microprocessor and firmware calculate gas
concentration, monitor the performance of the analyzer, keep track of
maintenance items, and control the output of data. The power supply board and
24V power supply provides the high voltage for the PMT, power to the PMT cooler
and the DC power for the electronics. The front panel display and keypad are used
for display of the data and the operation of the analyzer.
Analog, Printer and RS-232 Outputs
In addition to displaying data on the front panel, data can also be: sent to a
recorder or integrator using the analog output, sent to a computer using the RS-
232 output, and printed using the parallel printer port. The analog output can be
set to 0-1 V or 0-10 V full-scale. The printer output shows the minimum, maximum
and average value for a selected print interval ranging from 5 seconds to 10
minutes. The RS-232 output provides data at sampling rates from 32 samples per
second to 6 samples per minute.