VQ548ZD-S

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 VQ500 Series Datasheet Catalytic Combustible Gas Sensor (4-Series) The VQ500 Series is a complete range of miniature, fully certified, flameproof sensor heads containing a high quality, low power pellistor pair optimised for the detection of combustible gases or % volume gases in thermal conductivity mode. They have an outline identical to modern miniature electrochemical cells and are ideally suited for use in portable instruments. Within the VQ500 Series there are specific sensors that are able to detect most combustible gases and vapours and ammonia at LEL levels. The thermal conductivity version will detect most gases at % volume concentrations which have thermal conductivities different from that of air. The VQ500ZD/W variants have had a temperature test performed during its manufacture to confirm the temperature performance of the sensor meets the datasheet ensuring compliance to the various mining performance standards (Group 1) with regard to the temperature performance. The VQ548ZD-S variant has extra burn-in for enhanced stability. FEATURES • • • • • • • • • • • • • Optimised for combustible gases and vapours Thermal conductivity versions available Certified explosion proof component Integral pellistors Low power Standard miniature body size Poison resistant – silicones and hydrogen sulfide Shock resistant ATEX certified IECEx certified CSA certified UL recognised Temperature Rated between -40°C and +55°C If a flammable gas is present when the bead is heated to about 400 to 500 °C, the gas will oxidise and the resultant release of energy will heat the bead still further. This increase in temperature is detected as an increase in resistance of the coil. The temperature of the coil 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 bead is used. This compensator is made in the same way as a detector bead except that instead of incorporating a catalyst in the ceramic bead, the bead is treated so that oxidation cannot take place. The two beads are then used in a circuit that detects the difference in their resistances. Since the two beads are generally of a different colour, they have different emissivity and hence different slope resistances. Therefore, to obtain the best temperature performance, it is necessary to connect a fixed resistor in parallel with the compensator to correct for its higher slope resistance. TECHNICAL SPECIFICATION Mechanical Dimensions Body material Weight see outline, page 3 Stainless Steel 22g Environmental OPERATING PRINCIPLES The detector consists of a fine coil of platinum wire embedded in a ceramic bead incorporating a noble metal catalyst. The coil acts both as an electrical heater and as a resistance thermometer. The bead is mounted on a header with connecting leads and is surrounded by a metal can with the end open to the atmosphere. Temperature range for operation and storage Humidity range for operation and storage −40 to +55 °C 0 to 80% (non-condensing) Electrical Supply Voltage 3.00 V to 4.25 V; (Depending upon type) Supply Power 135 mW to 230 mW (Depending upon type) 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-0223, Issue 2, 10-May-2016, Page 1 SGX Europe Sp. z o.o. Building 11 Ligocka St. 103, 40-568 Katowice, Poland PERFORMANCE Linearity: Catalytic Thermal Conductivity Response Time (T90) Long Term Zero Drift ZD-S Variants All other Types Linear up 60%LEL Refer to Pellistor Application Note 5 T90 < 20 seconds