Rosemount 755R, Инструкция по эксплуатации

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T
HEORY
5-4
June 1997 Rosemount Analytical 748213-P Model 755R Oxygen Analyzer
F
IGURE
5-2. S
PHERICAL
B
ODY IN
N
ON
-U
NIFORM
M
AGNETIC
F
IELD
5.3 ELECTRONIC CIRCUITRY
Electronic circuitry is shown in the Control Board schematic diagram, Drawing 652826,
and is described briefly in the following sections. For detailed circuit analysis, refer to
Section 6, Circuit Analysis.
5.3.1 D
ETECTOR
/M
AGNET
A
SSEMBLY
A cross-sectional view of the optical bench and detector assemblies is shown in
Figure 5-3B. Source lamp DS1, powered by a supply section within the Power Supply
Board assembly (See Section 5.3.3) directs a light beam onto the mirror attached to
the test body. The mirror reflects the beam onto dual photocell BT1, BT2.
The difference between the signals developed by the two halves of the photocell
constitutes the error signal supplied to the input of amplifier U1 on the Control Board
assembly. Amplifier U1 drives U2 which, in turn, supplies the restoring current to the
titanium wire loop on the test body (See Section 5.1).
Detector temperature is sensed by thermistor RT1, an integral part of the detector
assembly (See Figure 5-3B). The thermistor provides the input signal to the detector
temperature control section of the Power Supply Board assembly: HR1, mounted on
the top of the magnet, and HR2, mounted permanently on the rear of the detector
assembly.
Shaded
Pole
Piece
Sphere
(Magnetic Susceptibility = k
o
)
F
k
Sample Gas
(Magnetic Susceptibility = k
)
Note:
As percentage of oxygen in sample gas increases,
displacement force (F
k
) increases.