ENMET PGD2 - Manual (Page 26)

ENMET Corporation PGD2
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12.1.2 0 - 100% Volume Flammable Sensors
For measurement of flammable gas concentrations up to 100% volume two pairs of pellistors are fitted one pair covering
measurements up to approximately the Lower Explosive Limit as specified in the previous section 12.1.1 and a second pair covering
measurements from the Lower Explosive Limit up to 100% volume.
The PGD2 instrument automatically switches between the pairs of pellistors according to the gas concentration present in order to
provide the most accurate reading.
The two pairs of pellistors are encapsulated into individual stainless steel housings. The LEL pellistors (both detector and
compensator) and the 100% volume detector pellistor are each behind individual stainless steel sintered flame arrestors while the
100% volume compensator housing is sealed.
The four individual stainless steel housings are contained within a black coloured plastic moulding which is normally mounted behind
the instruments’ right hand side gas inlet as viewed from the front.
Note that this arrangement represents the equivalent of two gas sensors such that instruments fitted with 0-100% flammable
sensors can only be fitted with an oxygen sensor plus one toxic sensor as a maximum.
Where an oxygen sensor is also fitted then this is mounted (via an oxygen sensor seal) behind the black coloured flammable sensor
housing.
Where a toxic sensor is also fitted then this must be of the ‘3 - series’ type e.g. 3CO, 3H, 3Cl etc.
0-100% Volume Flammable Sensor Specification
Gases detected
- Various combustible gases and vapors
Range
- 0 - 100% Volume
Resolution
- 0.05% Volume
Operating Voltage
- 2 ± 0.1 Volts dc
Operating Current
- 180 mA
T
90
Response Time - < 10 Seconds
Linearity
- Linear 0-5% Methane
Linearised over the range 5% to 100% via the instrument software
Long Term Sensitivity
Drift (0-5%)
- < 5% signal / month
Long Term Zero
Drift (0-5%)
- < 2% LEL methane / month
Range Changing -
Automatically carried out by the instrument