Rosemount 755R, Инструкция по эксплуатации

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T
HEORY
5-6
June 1997 Rosemount Analytical 748213-P Model 755R Oxygen Analyzer
The Control Board consists of signal conditioning and control circuitry.
This circuitry includes the following:
I
NPUT
A
MPLIFIER
U1
This amplifier receives the error signal from the dual photocell of the detector
assembly and drives amplifier U2.
A
MPLIFIER
U2
AND
A
SSOCIATED
Z
ERO
A
DJUSTMENT
Amplifier U2 supplies the restoring current to the titanium wire loop of the test body
within the detector assembly. Front panel ZERO Control R13 applies an adjustable
zero biasing signal to the input of U2 to permit establishing a zero calibration point on
the display or recorder. With zero standard gas flowing through the analyzer, the
ZERO control is adjusted for the appropriate reading.
A
MPLIFIER
U4
AND
A
SSOCIATED
S
PAN
A
DJUSTMENT
Amplifier U4 and associated feed back resistors provide a signal amplification of X4.
Front panel SPAN adjustment R20 modifies the value of the input resistance and
hence the signal amplification factor. Adjustment range is approximately
±
30%.
A
MPLIFIER
U8
This unity gain amplifier provides zeroing capability and a buffered output for the
anticipation circuit feeding U10.
A
MPLIFIER
U10
U10 is an inverting buffer amplifier that incorporates an anticipation arrangement in its
input network, thus providing slightly faster response on the readout device(s).
Potentiometer R30 provides a continuously variable adjustment of 5 to 25 seconds for
the electronic anticipation time and is factory-set for 20 seconds.
Since the anticipation network attenuates the signal, a gain of 10 is provided in U10 to
restore the signal to the desired fullscale range of 0 to 10 VDC.
The output signal from U10 is routed to two output circuits: a digital and an analog.
In the Digital Output Circuit, the signal from U10 passes to an integrating
analog-to-digital converter. The resulting digital signal drives the liquid crystal display.
In the Analog Output Circuit, the output from U10 is provided as an input to the
recorder output amplifier. This circuitry provides scale expansion, and amplification
preparatory to use for potentiometric recorder, voltage-to-current conversion for
current recorder, and/or alarm functions.