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 VQ548MP2-DA Datasheet MEMS Catalytic Combustible Gas Sensor (4-Series) The VQ548MP-DA is a low power, hazardous area safe, extremely robust and poison-resistant device in a certified flameproof enclosure. The VQ548MP2-DA type sensor is designed for low power operation in continuous mode providing additionally ultra-low power consumption when used in pulse mode operation, which makes this sensor a preferred choice for battery operated devices. The VQ548MP2-DA has been designed to provide the basic sensor performance that will enable a suitable instrument to The compensator is made in the same way as a detector device meet the various (Group 1) mining and industrial (Group 2) except that instead of incorporating a catalyst in the coating performance standards. layer, the device is treated so that oxidation cannot take place. Whilst being optimised for its methane response (up to 5% The two devices are then used in a circuit that detects the volume in air), will also detect some other flammable gases and difference in their resistances. Since the two devices are vapours. For further information, contact SGX Sensortech. generally a different colour, they have different emissivity and hence different slope resistances. Therefore, to obtain the best FEATURES temperature performance, it is necessary on occasion to connect a fixed resistor in parallel with the compensator to Low power designed for battery operation correct for its higher slope resistance. Small size (16 x 20 mm) Compatible with instruments using VQ500 type sensor TECHNICAL SPECIFICATION High resistance to mechanical shocks Assessed as intrinsically safe Mechanical Low orientation effect Dimensions see outline, page 4 ATEX Certified (II 1G Ex da IIC Ga, I M1 Ex da I Ma) Body material PEI IECEx certified (Ex da IIC Ga, Ex da I Ma) Weight 8g Environmental Ambient temperature range for operation / storage: 40 to +60 C certified: 40 to +60 C Operational pressure range 70 to 130 kPa OPERATING PRINCIPLE Humidity range for operation 0 to 95% and storage (non-condensing) The silicon pellistor structure consists of a pair of accurately Gases Detected Most flammable gases micro machined diaphragms with two embedded planar heater and vapours meanders coated with a layer incorporating a noble metal catalyst for the detector device and with inert layer for the compensator device. Electrical DC supply to detectors +2.9 to +3.1V The meander acts both as an electrical heater and as a Typical power 37.0 to 41.0 mA resistance thermometer. The device is mounted on a PCB with (<96mA at power on) wire bonding and is surrounded by a plastic can with the end (1) Mode of Operation Continuous or pulsed open to the atmosphere. If a flammable gas is present when the device is heated to about 400 500 C, the gas will oxidise (1) and the resultant release of energy will heat the device still Suggested minimum ON pulse time is 300ms. 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. 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-0301 VQ548MP2-DA, Issue 1, 08-Jan-2019, 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 Minimum sensitivity 8 mV/% methane (measured with 1% methane at 3.0 0.1V) without harm. The only effect is to reverse the polarity of the output signal. Zero offset range in clean air -30mV 20 mV 2. Maximum (slowest) response time measured at 3.0 0.1 V using 1% methane in an SGX test Response Time (T ) 90 < 12 sec manifold. Faster response times will be achieved in (See Note 2) instruments/detectors 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 (see note 4) operating, to gas concentrations greater than the Lower Long Term Sensitivity drift Explosive 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 VQ548MP2-DA to avoid erroneous readings and to prevent Pins 1 and 2 1.6 V the 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 OPERATION reaction of coating material used in pellistors. It is recommended that the detector and compensator be run Exposure to silicones (by far the most common & in a Wheatstone bridge circuit. virulent poison), high levels of hydrogen sulfide (and other sulfur containing compounds), phosphates and A suitable circuit is shown below. In use, the bridge supply phosphorous containing substances or lead voltage should be stable to within + 0.05 V, or the output in containing compounds (e.g. tetraethyl lead) will clean air may change in sympathy. Although it is generally irreversibly poison the sensor. High concentrations recommended that pellistors should be run with a constant of flammable gas may also permanently affect the voltage supply to the bridge, it is possible to use a constant sensor response. current supply provided that the voltage across the bridge in Lower concentrations of hydrogen sulfide and other clean air remains within the recommended limits. compounds can cause a temporary loss in response. This is known as inhibition. Halogenated Recommended circuit diagram 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 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. Under no circumstances should the sensor pins be soldered directly to a PCB or wires. Excessive heat could cause irreparable damage to sensor. Information on the recommended sockets can be found on our website under the Frequently Asked Questions (FAQ) section. Please contact SGX Sensortech for any additional information. SGX Sensortech 2019 Document subject to disclaimer on page 1 DS-0301 VQ548MP2-DA, Issue 1, 08-Jan-2019, Page 2