SGX Europe Sp. z o.o. T: +48 (0) 32 438 4778 Building 11 Ligocka St. 103, E: sales.is sgxsensortech.com 40-568 Katowice, www.sgxsensortech.com Poland MP-7217 Datasheet MEMs Catalytic Combustible Gas Sensor (Miniature) 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 SGX Sensortech. FEATURES Low power designed for battery operation This compensator is made in the same way as a detector Small size (14mm) device except that instead of incorporating a catalyst in the High resistance to mechanical shocks coating layer, the device is treated so that oxidation cannot take place. Assessed as intrinsically safe Low orientation effect The two devices are then used in a circuit that detects the ATEX Certified difference in their resistances. Since the two devices are generally a different colour, they have different emissivity and IECEx certified hence different slope resistances. Therefore, to obtain the best UL Recognised - File E186043 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 Dimensions see outline, page 4 OPERATING PRINCIPLE Body material PEI The silicon pellistor structure consists of a pair of accurately Weight 1g micro machined diaphragms with two embedded planar heater meanders coated with a layer incorporating a noble metal Environmental catalyst for the detector device and with inert layer for the Ambient temperature range compensator device. for operation / storage: 40 to +60 C certified: 40 to +75 C The meander acts both as an electrical heater and as a resistance thermometer. The device is mounted on a PCB with Operational pressure range 70 to 130 kPa wire bonding and is surrounded by a plastic can with the end Humidity range for operation 0 to 95% open to the atmosphere. If a flammable gas is present when the and storage (non-condensing) device is heated to about 400 500 C, the gas will oxidise and Gases Detected Most flammable gases the resultant release of energy will heat the device still further. and vapours This increase in temperature is detected as an increase in resistance of the meander. The temperature of the meander is Electrical also affected by ambient temperature and by variations in thermal conductivity of the air caused by the possible presence DC supply to detectors +2.9 to +3.1V of inert gases such as carbon dioxide. To compensate for Typical power 39 to 47mA temperature changes not caused by the oxidation of the (<96mA at power on) flammable gas a second, inert device is used. Mode of Operation Continuous 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. T: +48 (0) 32 438 4778 Building 11 Ligocka St. 103, E: sales.is sgxsensortech.com 40-568 Katowice, www.sgxsensortech.com Poland PERFORMANCE NOTES 1. The polarity of the supply voltage may be reversed without Minimum sensitivity 12 mV/% methane (measured with 1% methane at 3.0 0.1V) harm. The only effect is to reverse the polarity of the output signal. Zero offset range in clean air 20 mV 2. Maximum (slowest) response time measured at 3.0 0.1 V using 1% methane in an SGX test manifold. Faster Response Time (T ) 90 < 12 sec response times will be achieved in instruments/detectors (See Note 2) with optimised gas delivery. Maximum gas concentration 5% methane in air 3. Exceeding these limits may degrade the stability of (see note 3) sensitivity or zero offset. The calibration of the sensor Long Term Zero drift < 1.0 mV / month should be checked if it has been exposed, whilst operating, (see note 4) to gas concentrations greater than the Lower Explosive Long Term Sensitivity drift Limit. < 0.6 mV / month (see note 5) 4. Over 90 day period. 5. Measured at 3.0 0.1V using 1% methane, over 90 days period. MAXIMUM RATINGS (Absolute values) Input voltages between pins: IMPORTANT PRECAUTIONS Pins 2 and 3 3.2 V Read the following instructions carefully before using the MP- 7217 to avoid erroneous readings and to prevent the device Pins 1 and 2 1.6 V from permanent damage. Pins 1 and 3 1.6 V Heater voltages above the specified maximum rating can damage the MEMS Pellistor. Some compounds are known to affect the catalytic reaction OPERATION of coating material used in pellistors. It is recommended that the detector and compensator be run in Exposure to silicones (by far the most common & virulent a Wheatstone bridge circuit. poison), high levels of hydrogen sulfide (and other sulfur containing compounds), phosphates and phosphorous A suitable circuit is shown below. In use, the bridge supply containing substances or lead containing compounds voltage should be stable to within + 0.05 V, or the output in (e.g. tetraethyl lead) will irreversibly poison the sensor. clean air may change in sympathy. Although it is generally High concentrations of flammable gas may also recommended that pellistors should be run with a constant permanently affect the sensor response. voltage supply to the bridge, it is possible to use a constant Lower concentrations of hydrogen sulfide and other current supply provided that the voltage across the bridge in compounds can cause a temporary loss in response. clean air remains within the recommended limits. This is known as inhibition. Halogenated hydrocarbons such as Freons, trichloroethylene, and methyl chloride Recommended circuit diagram are also possible inhibitors. Sensors generally recover most of their original response once they are returned to fresh air. 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 elements. Please contact SGX Sensortech for any additional information. SGX Sensortech 2016 Document subject to disclaimer on page 1 DS-0165, Issue 5, 03-May-2016, Page 2