Heath Consultants Detecto-Pak 4 (DP) - Manual (Page 28)

O
peration
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13. To check pulsating signal alarm operation by press zero up switch
until pulsating alarm sounds. Allow time for the meter to settle. The
pulsating alarm should turn on at a meter reading between 35-45%
of full scale. Return meter reading to zero.
14. To verify that the instrument is operational, the Detecto-Pak 4’s
sensitivity should be tested by introducing a small sample of a
known hydrocarbon gas to the sample inlet. The meter should swing
upscale and return to zero.
15. The Detecto-Pak 4 is now operational.
C. ZERO PROCEDURES
Zero the instrument as needed by the following procedure.
Before zeroing the Detecto-Pak 4, two conditions must be met:
1. The instrument must be fully charged, and
2. Either zero air from a demand regulator or a verified hydrocarbon
free atmosphere must be used. Zero air is recommended. The Average
background level of methane in the atmosphere is 2 ppm.
Zeroing Procedure:
a. With the instrument’s power off, mechanically zero the meter using
a small blade screwdriver.
b. Start and warm-up the instrument as described under “OPERATING
PROCEDURES’, Chapter Five, Section V, B.
c. Coarse zero the instrument on the 10 K ppm range. A micro
screwdriver will be needed to adjust the potentiometer (RP8)
located behind the right-hand (inner most) access plug on the rear
of the instrument below the fuel bottle holder. Remove the plug to
access the adjusting potentiometer. Refer to Figures 7 and 8 in the
manual.
**NOTE**
The fine zero control is automatically centered upon power-up. Do not
adjust the fine zero (by using the zero controls on the top panel) at this time.
d. Select the 50 ppm range and re-adjust the coarse zero.
e. Re-insert the plug into the right hand access port.