Table des Matières
Publicité
Les langues disponibles
Les langues disponibles
3. Operation
WARNING
Prior to carrying out any work ensure local regulations and site procedures are
followed. Never attempt to open the detector or junction box when flammable
gas is present. Ensure that the associated control panel is inhibited so as to
prevent false alarms.
3.1 Commissioning procedure
1. Open the junction box of the detector by unscrewing the lid in an anti-clockwise
direction (having loosened the retaining grub-screw first).
2. Check that all electrical connections have been made and are correct, as shown in
Diagram 5.
3. Measure the voltage across the '+' and '-' terminals and check a minimum supply of
10 V d.c. is present.
4. Leave the detector to stabilise for at least 45 minutes.
5. To zero the detector, connect the DVM to the test points marked 'TP1' and 'TP2' on
the amplifier PCB, as shown in Diagram 4.
Note: At the test points, Zero will read 40 mV = 4 mA.
Full scale deflection will read 200 mV = 20 mA. There is a current clamp of 25 mA
on the 4-20 mA output.
Zeroing the detector
6. Ensure you are in clean air. Adjust the 'ZERO' pot on the amplifier (which is acces-
sible via a hole in the PCB cover) until the DVM reads 40 mV. Check that the control
equipment display reads zero.
Calibrating the detector
7. Apply calibration gas (concentration should ideally be at least 50% of full scale
concentration) to the detector at a flow rate of 0.5–1 litre/minute via a flow adaptor
(Part No. C03005). Contact Crowcon for the supply of calibration gas.
8. Allow the gas reading to stabilise (usually 30 to 60 seconds) and adjust the 'CAL'
pot until the DVM reads the appropriate reading (eg for a hydrocarbon gas detector
120 mV = 12 mA = 50% LEL). If the concentration of the calibration gas used is not
50% of scale, the following formula can be used to calculate the reading:
160
Gas
×
+
Range
Example: calibrating a 0-5% CO
16
40
mV setting
=
detector using 3% CO
2
test gas
2
Publicité
Table des Matières
