Instruction Manual

245364-V

Model 755A

May 2002

Where:

 

b.

Physical Configuration of

c = A function of the magnetic field

Detector/Magnet Assembly

strength and gradient

As shown in Figure 4-3A (page 4-4), the

 

k = Magnetic susceptibility of the

Detector/Magnet Assembly consists of

surrounding gas

three major components; the magnet

 

assembly, the detector assembly and the

ko = Magnetic susceptibility of the

optical bench assembly.

sphere

The magnet assembly includes a sample

 

The forces exerted on the two spheres of

pre-heating coil. It is connected into the

the test body are thus a measure of the

sample line upstream from the detector

magnetic susceptibility of the sample and,

and is heated to approximately the same

therefore, of its oxygen content.

temperature as the detector assembly.

 

For convenience in servicing, the detector

 

and the optical bench are self-aligning

 

assemblies that utilize slip-on sample

Shaded

connections and plug-in electrical

connections.

Pole

Piece

 

Sphere

Within the detector assembly, Figure 4-3B

(page 4-4), the incoming preheated

(Magnetic Susceptibility = ko )

sample passes through an integral 5

 

 

micron diffusion screen. It protects the

 

test body by preventing entry of

 

particulate matter and/or entrained liquid

Fk

mist. Additionally, the screen isolates the

 

test body from flow effects, ensuring that

 

instrument readout is relatively

 

independent of flow rate within the

 

optimum range of 200 to 300 cc/min.

Sample Gas

(Magnetic Susceptibility = k )

Note:

As percentage of oxygen in sample gas increases, displacement force (Fk ) increases.

Figure 4-1. Spherical Body in Non-Uniform

Magnetic Field

At the rear of the detector are an integral temperature sensor (RT1) and an integral heater (HR2). Another heater (HR1) is attached to the magnet. Sensor RT1 provides the input signal to the detector temperature control circuit of the Case Board assembly, Section 4-3c (page 4-7). This circuit controls application of electrical power to both HR1 and Hr2.

On the optical bench assembly, Figure

4-3C (page 4-4), the source lamp and the photocell plate are externally accessible, permitting convenient replacement.

4-2

Theory

Rosemount Analytical Inc. A Division of Emerson Process Management