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-DA Datasheet MEMs 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. This compensator is made in the same way as a detector device except that instead of incorporating a catalyst in the FEATURES coating layer, the device is treated so that oxidation cannot take place. Low power designed for battery operation Small size (14mm) The two devices are then used in a circuit that detects the High resistance to mechanical shocks difference in their resistances. Since the two devices are generally a different colour, they have different emissivity and Assessed as intrinsically safe hence different slope resistances. Therefore, to obtain the best Low orientation effect temperature performance, it is necessary on occasion to ATEX Certified connect a fixed resistor in parallel with the compensator to correct for its higher slope resistance. IECEx certified TECHNICAL SPECIFICATION Mechanical Dimensions see outline, page 4 Body material PEI Weight 1g OPERATING PRINCIPLE Environmental The silicon pellistor structure consists of a pair of accurately micro machined diaphragms with two embedded planar heater Ambient temperature range meanders coated with a layer incorporating a noble metal for operation / storage: 40 to +60 C catalyst for the detector device and with inert layer for the certified: 40 to +60 C compensator device. Operational pressure range 70 to 130 kPa Humidity range for operation 0 to 95% The meander acts both as an electrical heater and as a and storage (non-condensing) resistance thermometer. The device is mounted on a PCB with Gases Detected Most flammable gases wire bonding and is surrounded by a plastic can with the end and vapours 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. Electrical This increase in temperature is detected as an increase in DC supply to detectors +2.9 to +3.1V resistance of the meander. The temperature of the meander is Typical power 39 to 47mA also affected by ambient temperature and by variations in (<96mA at power on) thermal conductivity of the air caused by the possible presence Mode of Operation Continuous 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. 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-0165, Issue 7, 14-Jun-2018, 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 harm. The only effect is to reverse the polarity of the output (measured with 1% methane at 3.0 0.1V) 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-DA to avoid erroneous readings and to prevent the Pins 1 and 2 1.6 V device 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 2018 Document subject to disclaimer on page 1 DS-0165, Issue 7, 14-Jun-2018, Page 2