MP-7217 Sensor Datasheet
Catalytic Combustible Gas Sensor
|Total Page||4 Pages|
SGX Europe Sp. z o.o.
Ligocka St. 103,
T: +48 (0) 32 438 4778
MEM’s Catalytic Combustible Gas Sensor
This datasheet describes the use of the MP-7217 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 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 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
• 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
• UL Recognised - File E186043
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
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.
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
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.
see outline, page 4
Ambient temperature range
for operation / storage:
Operational pressure range
Humidity range for operation
−40 to +60 °C
−40 to +75 °C
70 to 130 kPa
0 to 95%
Most flammable gases
DC supply to detectors
Mode of Operation
+2.9 to +3.1V;
39 to 47mA
(<96mA at power on)
Whilst SGX has taken care to ensure the accuracy of the information contained herein it accepts no responsibility for the consequences of any use thereof and also
reserves the right to change the specification of goods without notice. SGX accepts no liability beyond the set out in its standard conditions of sale in respect of
infringement of third party patents arising from the use of SGX products in accordance with information contained herein.
In case of modification of the product, SGX disclaims all liability.
SGX Europe sp .z o.o. Poland REGON: 362332227
DS-0140, Issue 6, 03-May-2016, Page 1
SGX Europe Sp. Z o.o.
Ligocka St. 103,
T: +48 (0) 32 438 4778
(measured with 1% methane at 3.0 ± 0.1V)
Zero offset range in clean air
Response Time (T90)
(See Note 2)
Maximum gas concentration
(see note 3)
Long Term Zero drift
(see note 4)
Long Term Sensitivity drift
(see note 5)
12 mV/% methane
± 20 mV
< 12 sec
5% methane in air
< 1.0 mV / month
< 0.6 mV / month
MAXIMUM RATINGS (Absolute values)
Input voltages between pins:
Pins 2 and 3
Pins 1 and 2
Pins 1 and 3
It is recommended that the detector and compensator be run in
a Wheatstone bridge circuit.
A suitable circuit is shown below. In use, the bridge supply
voltage should be stable to within + 0.05 V, or the output in
clean air may change in sympathy. Although it is generally
recommended that pellistors should be run with a constant
voltage supply to the bridge, it is possible to use a constant
current supply provided that the voltage across the bridge in
clean air remains within the recommended limits.
Recommended circuit diagram
1. The polarity of the supply voltage may be reversed without
harm. The only effect is to reverse the polarity of the output
2. Maximum (slowest) response time measured at 3.0 ± 0.1 V
using 1% methane in an SGX test manifold. Faster
response times will be achieved in instruments/detectors
with optimised gas delivery.
3. Exceeding these limits may degrade the stability of
sensitivity or zero offset. The calibration of the sensor
should be checked if it has been exposed, whilst operating,
to gas concentrations greater than the Lower Explosive
4. Over 90 day period.
5. Measured at 3.0 ± 0.1V using 1% methane, over 90 days
Read the following instructions carefully before using the MP-
7217 to avoid erroneous readings and to prevent the device
from permanent damage.
• Heater voltages above the specified maximum rating can
damage the MEMS Pellistor.
• Some compounds are known to affect the catalytic reaction
of coating material used in pellistors.
• Exposure to silicones (by far the most common & virulent
poison), high levels of hydrogen sulfide (and other sulfur
containing compounds), phosphates and phosphorous
containing substances or lead containing compounds
(e.g. tetraethyl lead) will irreversibly poison the sensor.
High concentrations of flammable gas may also
permanently affect the sensor response.
• Lower concentrations of hydrogen sulfide and other
compounds can cause a temporary loss in response.
This is known as inhibition. Halogenated hydrocarbons
such as Freons™, trichloroethylene, and methyl chloride
are also possible inhibitors. Sensors generally recover
most of their original response once they are returned to
• Specific protection may be needed in applications where
poisons or inhibitors are continuously present.
• SGX recommends using ESD protection equipment when
handling the sensor.
• Care should be taken when soldering the device as
excessive heat could cause irreparable damage to sensor
• Please contact SGX Sensortech for any additional
© SGX Sensortech 2016
Document subject to disclaimer on page 1
DS-0165, Issue 5, 03-May-2016, Page 2
|Features||SGX Europe Sp. z o.o. Building 11 Ligock a St. 103, 40-568 Katowice, Poland T: +48 (0) 32 438 4778 E: sales.is@sgxsens ortech.com www.sgxsensortech.com MP-72 17 Datasheet MEM’s Catalytic Combust ible Gas Sensor (Miniature) This datas heet describes the use of the MP-7217 P ellistor. This is commonly used, but no t exclusively, in mining applications. It is a low power, intrinsically safe, extremely robust and poisonresistant de vice in a certified flameproof enclosur e. The MP-7217 has been designed to pro vide the basic sensor performance that will enable a suitable instrument to me et the various (Group 1) mining perform ance standards. The MP-7217 sensors, wh ilst being optimised for its methane re sponse (up to 5% volume in air), will a lso detect some other flammable gases a nd vapours. For further information, co ntact SGX Sensortech. FEATURES • Low power – designed for battery operatio n • Small size (Ø14mm) • High resi stance to mechanical shocks • Assessed as intrinsically safe .|
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