Emerson Rosemount CCO 5500, Reference Manual

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2. In the control unit trim, potentiometers adjust the level of the D1 and D2 signals
before they enter the microprocessor. Refer to
Section 3.5.1 .
It is essential that you properly conduct the alignment procedure and obtain a maximum
detector signal before attempting to optimize the detector levels.
3.5.1 Receiver gain adjustment
To give an optimum signal-to-noise ratio, the detector levels must be maximized. For the
best signal-to-noise ratio, you must set the gain of the detector signals in the receiver to a
maximum without saturating. Rosemount
™
sets the gains at a path length of 6.5 f.t (2 m).
If the path length is above 13 ft (4 m) or below 5 ft (1.5 m), you may need to adjust to
optimize the detector levels.
1.
Enter Mode 5
→
Calibrate
→
Set Detectors and display the value of D2/D1.
2. Loosen the receiver cable gland so the receiver cable can slip when you remove the
window plate.
3. Pull the window plate ( Figure 3-4 ) from the receiver to access the detectors.
Receiver Trim Pots Figure 3-4:
A. Trim pot for end detector D1
B. Trim pot for side detector D2
4. Trim potentiometer(s) set the gain.
An AC voltmeter measures the gain levels.
5. Connect the voltmeter to the test points on the control unit (18/20 for D1 and
19/20 for D2). Increase the gain using the trim pot at the end detector D2 until the
voltage is between 1 - 4 Vac.
Configuration and startup
30 Rosemount CCO 5500