Manual CWD 2005 Measurement principle
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Manual CWD2005.doc 89
9.2.6. Testing and calibration
Specific gravity cell function can be tested using 2 gases. The specific gravity of the
two gases should differ by more than 0.5 so that the zero and span can be checked.
If non-flammable gases are used, such as N
2
or air, the ignition cycle will time out so
set the purge time to a high value so the solenoid valve remains open and the gas
will flow. Restore any program data after testing and crosscheck the results.
9.2.7. Maintenance
The specific gravity cell requires no regular maintenance. From time to time, the
pressure drop across the density cell should be checked. After installation the sensor
housing must be able to move freely on the springs.
A defective specific gravity cell can be sent in for repair. The output for calorific value
can be turned off in the software and the unit will now measure Wobbe Index only.
9.2.8. Technical specifications
1
9
gas-inlet
ST2
Insulation
1
2
3
4
gas-outlet
LFE 209C
Figure 20: Specific gravity measuring cell, heated and insulated
1. Potentiometer 1 Zero 3. Suspension springs
2. Potentiometer 2 Span 4. Insulating discs
ST2 PIN terminals
1 + 15 V Power Supply 7 VA
2 - 15 V Power Supply 7 VA
3 Location pin
4 Ground
5 Not Connected
6 Location pin
7 + 5 V Measurement signal
8 Not Connected
9 Ground Specific Gravity 0-5 Volt
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