
Instruction Manual
Refer to Figure
The test body is constructed of two hollow glass spheres forming a dumbbell shape. They are filled and sealed with pure, dry nitro- gen. Around the test body, a titanium wire is chemically etched in order to form a feedback loop that can create a counteracting magnetic force to the test body displacement caused by oxygen concentration in the test assembly magnetic field.
Attached to the center arm of the test body dumbbell is a
The detector operates in the following fashion. If the sample gas contains oxygen, it collects in the
A light source is focused on the test body mir- ror. As the test body moves out of the magnetic field, the mirror distributes light unevenly on two photocells (BT1 and BT2). The photocells create a current proportional to light. This current is converted to a ± voltage by U1 and U2 located on the connector board in the detector housing. This voltage is then presented to comparator U1 on the controller board. The output of U1 goes to U2. The output of U2 causes current to flow through the feedback loop attached to the dumbbell.
This feedback current creates an electro
Model 755R
formly on each photocell. A current proportional to the oxygen concentration in the magnetic field of the test assembly has to be flowing through the feedback loop in order to maintain balance and provide a reading of the oxygen content of a sample.
Resistances R7, R8 and the resistance of the wire in the feedback loop determine the gain of amplifier U2. The mirror on the dumbbell is positioned by the amount of current in the feedback loop. The mirror reflects light from the source (DS1) to the photocells (BT1, BT2). This repositioning of the mirror is a form of mechanical feedback to the input of the amplifier U1.
The net result is that the output of U1 could vary from 0 to
Diode CR2 is a
If the dumbbell was out of position on
On application of AC power, capacitor C1 has no charge. The current will have to flow through R2. Initially the full 30 V drop (the difference between the +15 VDC and
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