
Instruction Manual
Model 755R
Shaded
Pole
Piece
Sphere
(Magnetic Susceptibility = ko )
Fk
Sample Gas
(Magnetic Susceptibility = k )
Note:
As percentage of oxygen in sample gas increases, displacement force (Fk ) increases.
Figure
Electronic circuitry is shown in the Control Board schematic diagram, Drawing 652826, and is described briefly in the following sec- tions. For detailed circuit analysis, refer to Section 5 Circuit Analysis.
a.Detector/Magnet Assembly
A
The difference between the signals de- veloped 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
Detector temperature is sensed by thermistor RT1, an integral part of the detector assembly (See Figure
b.Control Board and Associated Cir- cuitry
The Control Board consists of signal conditioning and control circuitry.
This circuitry includes the following:
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