"MicroPel" sensor operated at lower power (providing longer operation time per charge)
Can be Classified as Intrinsically Safe (versus "Flame Proof" classification carried by traditional pellistor sensors)
Faster response to gas due to elimination of T6 stainless steel flame arrestor (sinter)
Unmatched active bead and compensator require longer stabilization time
Because sensor runs at 3.0 versus 3.3 V, less able to "cook off" poisons and inhibitors
Low-power pellistor issues
Volume of pellistor bead (a sphere): V = 4/3 Π r3
Since most catalyst sites are within the bead (not on the surface of the bead), when you decease the radius of the bead by "x", you reduce the volume of the bead (and number of catalyst sites) by "x" to the third power ( x3 )
So, smaller low power LEL sensors are much easier to poison.
Silicones
Hydrogen sulfide
Other sulfur containing compounds
Phosphates and phosphorus containing substances
Lead containing compounds (especially tetraethyl lead)
Allow enough time for full stabilization prior to performing fresh air zero
DO NOT PERFORM AUTO ZERO AS PART OF AUTOMATIC STARTUP SEQUENCE
Perform functional test before each day's use!
Use methane based test gas mixture OR if you use a different gas (e.g. propane or pentane) challenge the sensor with methane periodically to verify whether the sensor has disproportionately lost sensitivity to methane
High Range Catalytic LEL Combustible Sensor Limitations
Even with protective circuitry that protects bead at concentrations above 100% LEL, no direct display of gas concentration
Techniques for high range combustible gas measurement:
Dilution fittings
Thermal conductivity sensors
Calculation by means of oxygen displacement
Using infrared (NDIR) sensor to measure combustible gas avoids all of these issues!
