CATALYTIC PELLISTORS GAS SENSORS

 

Our Pellistor, or catalytic bead sensor, line is selected by N.E.T. and manufactured, on OEM basis, by the companies leading in the field.
The sensor monitors the presence of a combustible gas or vapor in air (or atmospheres containing oxygen) up to the Lower Explosive Limit (LEL). A Pellistor operates on the principle that when a combustible gas/air mixture is in contact with the catalyst surface, maintained at about 500°C as current is passed through it in a Platinum coil, combustion occurs. The heat generated increases the temperature of the bead, which in turn changes the resistance of the coil. The resistive signal change produced is proportional to the gas concentration and can be measured by using the coil as a temperature thermometer in a standard Wheatstone bridge circuit.

Given Pellistors capacity to ignite flammable gas mixtures, is typically necessary to encapsulate the beads in a certified flameproof enclosure, such as N.E.T. Heads. This will allow the beads to be exposed to the target gas without the risk of ignition.

Pellistors are an inexpensive and effective solution to monitor Methane (CH4) and other Hydrocarbons and, generally, combustible gases such as Hydrogen (H2) and Ammonia (NH3). They offer very low humidity and temperature dependence.

As their measurement principle is based on combustion, Pellistors cannot be used in inert atmospheres and require the presence of Oxygen. Additionally, they are susceptible to inhibition and poisoning by chemicals such as Lead- and Sulphur-containing compounds, phosphates and organic silicones. In case any of those two risks are present, try our InfraRed sensors.

The standard dimensions and the electrical output make our Pellistor perfectly compatible with a wide range of commercially available Gas Detection Systems and remote flammable gas detector heads.

N.E.T. line of Pellistors includes:

SHM/SHP Pellistors (Single Head – Safety Line)
Consist of a matched pair of elements mounted on a single header and protected by a metal mesh filter.
Have a standard 4-series enclosure (D20.4 mm x H100) to fit a standard gas detector.
SHM housing is of stainless steel, while SHP’s is of plastic.

  • NP-17SHM or NP-17SHP: Single header pellistor with high temperature range (150°C/-40°C).
  • NP-18SHM or NP-18SHP: Single header pellistor for hydrocarbon in % LEL range. Ammonia and Hydrogen detection is possibile powering the sensor at a different Voltage.
  • NP-30SHM or NP-30SHP: Low cost version of NP-30SMM mounted on single header. Excellent long term stability

 

SMM (Matched Pair – Sensor Replacement  for NET3 / NETC3 Detector Heads)
Consist of a matched pair of elements mounted on T04 size headers and protected by a metal can.
The matched pair sensor is housed in standard 7-series plastic enclosure (D32 mm x H100) to fit a standard gas detector.

 

  • NP-30SMM
  • NP-18SMM
  • NP-17SMM
  • NP-ACSMM:  is a special-purpose pellistor sensor, designed to monitor %LEL levels of Acetylene with outstanding poison resistance.