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T
ROUBLESHOOTING
748250-L Rosemount Analytical October 1999
5-5
Model 880A Non-Dispersive Infrared Analyzer
B. Tank Circuit Resonance Curves
Curve 3. Sample beam blocked, causing maximum
distention of diaphragm.
Curve 2. OSCILLATOR TUNE Control set for .75% to 80%
of maximum obtainable meter reading.
Curve 1. OSCILLATOR TUNE Control set for
maximum obtainable meter reading.
Amplitude with Sample
Beam Blocked
75% to
80% of
max.
Max. Obtainable
Amplitude
Tank Circuit
Resonant Frequency
Crystal Frequency
(10 MHz)
Carrier
Amplitude
Note:
Decrease in inductance and/or capacitance in tank
circuit shifts resonance curve to right, decreasing
carrier amplitude.
Detector Oscillator
Tune Output
Diaphragm at
maximum
Distention
Stationary
Metal Button
A. Functional Diagram - Circuitry in Tune Mode
OSC. TUNE
L1
10 MHz
Oscillator
Tank Circuit
Voltage Doubler Rectifier
Diaphragm Undistended
DETECTOR
Reference
Chamber
Sample
Chamber
value for Step 5. (If this reading exceeds 1.2 V, then a Source Alignment is
necessary; see Section 5.7.)
5. Rotate the shutter adjust screw clockwise (viewed from the screw head) until the
display reads the value obtained in Step 4.
6. Re-tighten the locking nut. Ensure that the display does not change.
F
IGURE
5-2. M
ODULATION
S
YSTEM
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