SGX Europe Sp. z o.o.
Building 11
Ligocka St. 103,
40-568 Katowice,
Poland
T: +48 (0) 32 438 4778
E: sales.is@sgxsensortech.com
www.sgxsensortech.com
MP-7217-DA Datasheet
MEM’s Catalytic Combustible Gas Sensor
(Miniature)
This datasheet describes the use of the MP-7217-DA Pellistor.
This is commonly used, but not exclusively, in mining
applications. It is a low power, intrinsically safe, extremely
robust and poison-resistant device in a certified flameproof
enclosure.
The MP-7217-DA has been designed to provide the basic
sensor performance that will enable a suitable instrument to
meet the various (Group 1) mining performance standards.
The MP-7217-DA sensors, whilst being optimised for its
methane response (up to 5% volume in air), will also detect
some other flammable gases and vapours. For further
information, contact SGX Sensortech.
FEATURES
•
Low power – designed for battery operation
•
Small size (Ø14mm)
•
High resistance to mechanical shocks
•
Assessed as intrinsically safe
•
Low orientation effect
•
ATEX Certified
•
IECEx certified
This compensator is made in the same way as a detector
device except that instead of incorporating a catalyst in the
coating layer, the device is treated so that oxidation cannot take
place.
The two devices are then used in a circuit that detects the
difference in their resistances. Since the two devices are
generally a different colour, they have different emissivity and
hence different slope resistances. Therefore, to obtain the best
temperature performance, it is necessary on occasion to
connect a fixed resistor in parallel with the compensator to
correct for its higher slope resistance.
TECHNICAL SPECIFICATION
Mechanical
OPERATING PRINCIPLE
The silicon pellistor structure consists of a pair of accurately
micro machined diaphragms with two embedded planar heater
meanders coated with a layer incorporating a noble metal
catalyst for the detector device and with inert layer for the
compensator device.
The meander acts both as an electrical heater and as a
resistance thermometer. The device is mounted on a PCB with
wire bonding and is surrounded by a plastic can with the end
open to the atmosphere. If a flammable gas is present when the
device is heated to about 400 – 500 °C, the gas will oxidise and
the resultant release of energy will heat the device still further.
This increase in temperature is detected as an increase in
resistance of the meander. The temperature of the meander is
also affected by ambient temperature and by variations in
thermal conductivity of the air caused by the possible presence
of inert gases such as carbon dioxide. To compensate for
temperature changes not caused by the oxidation of the
flammable gas a second, inert device is used.
Dimensions
Body material
Weight
see outline, page 4
PEI
1g
Environmental
Ambient temperature range
for operation / storage:
certified:
Operational pressure range
Humidity range for operation
and storage
Gases Detected
−40 to +60 °C
−40 to +60 °C
70 to 130 kPa
0 to 95%
(non-condensing)
Most flammable gases
and vapours
Electrical
DC supply to detectors
Typical power
Mode of Operation
+2.9 to +3.1V;
39 to 47mA
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