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 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. If a flammable gas is present when the bead is heated to The VQ500ZD/W variants have had a temperature test about 400 to 500 C, the gas will oxidise and the resultant performed during its manufacture to confirm the release of energy will heat the bead still further. This increase temperature performance of the sensor meets the in temperature is detected as an increase in resistance of the datasheet ensuring compliance to the various mining coil. performance standards (Group 1) with regard to the temperature performance. The temperature of the coil is also affected by ambient temperature and by variations in thermal conductivity of the The VQ548ZD-S variant has extra burn-in for enhanced air caused by the possible presence of inert gases such as stability. carbon dioxide. To compensate for temperature changes not caused by the oxidation of the flammable gas a second, inert FEATURES bead is used. This compensator is made in the same way as a detector bead except that instead of incorporating a catalyst Optimised for combustible gases and vapours in the ceramic bead, the bead is treated so that oxidation Thermal conductivity versions available cannot take place. The two beads are then used in a circuit Certified explosion proof component that detects the difference in their resistances. Since the two Integral pellistors beads are generally of a different colour, they have different Low power emissivity and hence different slope resistances. Therefore, to Standard miniature body size obtain the best temperature performance, it is necessary to Poison resistant silicones and hydrogen sulfide connect a fixed resistor in parallel with the compensator to Shock resistant correct for its higher slope resistance. ATEX certified IECEx certified TECHNICAL SPECIFICATION CSA certified UL recognised Mechanical Temperature Rated between -40C and +55C Dimensions see outline, page 3 Body material Stainless Steel Weight 22g Environmental Temperature range for 40 to +55 C operation and storage OPERATING PRINCIPLES Humidity range for operation 0 to 80% and storage (non-condensing) The detector consists of a fine coil of platinum wire embedded in a ceramic bead incorporating a noble metal Electrical catalyst. The coil acts both as an electrical heater and as a Supply Voltage 3.00 V to 4.25 V resistance thermometer. The bead is mounted on a (Depending upon type) header with connecting leads and is surrounded by a Supply Power 135 mW to 230 mW metal can with the end open to the atmosphere. (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. T: +48 (0) 32 438 4778 Building 11 Ligocka St. 103, E: sales.is sgxsensortech.com 40-568 Katowice, www.sgxsensortech.com Poland PERFORMANCE OPERATION The output of a sensor is dependent on a complex Linearity: combustion process established around the sensing Catalytic Linear up 60%LEL beads. It is imperative that the layers of gas around the Thermal Conductivity Refer to Pellistor Application beads are not disturbed, otherwise the bead temperature Note 5 and hence device output will change. The design of the Response Time (T ) 90 T < 20 seconds 90 VQ500 housing achieves this requirement, provided the Long Term Zero Drift user takes care not to allow gas flows directly onto the - ZD-S Variants <5%LEL / month sinter. (based upon a 1 month period) - All other Types <5%LEL / month It is recommended that the detector and compensator be (based upon a 12 month period) run in a Wheatstone Bridge circuit so that a difference Long Term Sensitivity Drift signal may be obtained. A suitable circuit is shown in this - ZD-S Variants <5%Full-Scale / month document. In use, the bridge supply voltage should be (based upon a 1 month period) stable to within + 0.1 V, or the output in clean air may - All other Types <5% Full-Scale / month (based upon a 12 month period) change in sympathy. Although it is generally recommended that pellistors should be run with a constant Zero Offset with Temperature 0.2% methane variation voltage supply to the bridge, it is possible to use a (ZD/W Variant Only) between -10C to +40C constant current supply provided that the voltage across when compare to the 20C the bridge in clean air remains within the recommended reading limits. Warranty Period 12 months MAXIMUM GAS CONCENTRATIONS (See Note d) 100%v/v VQ546M, VQ546MR 100%LEL VQ547TS, VQ548, VQ549 NOTES a) The sensitivity is measured in the standard manufacturers test jig with no filter or other material between the gas and the sinter. b) A temperature test is performed on all ZD/W sensors to confirm the temperature performance of the sensor is within specification. c) A burn-in for several weeks is performed followed by a week drift test. d) The calibration of the sensor should be checked if it has been exposed, whilst operating, to gas concentrations greater than the Lower Explosive Limit. Exceeding this limit may permanently damage the sensor. e) It is not recommended to direct the gas flow onto the sinter. f) The response to flammable vapours, especially heavy aromatic compounds, may be different to the theoretical figures (k factors) listed in Pellistor Application Note 3. These k factors are for guidance only and ideally the sensors should be calibrated to the actual vapour concentration required. g) Under no circumstances should the sensor pins be soldered directly to a PCB or wires. Excessive heat could cause irreparable damage to sensor elements. Information on the recommended sockets can be found on our website under the Frequently Asked Questions (FAQ) section. SGX Sensortech 2016 Document subject to disclaimer on page 1 DS-0223, Issue 2, 10-May-2016, Page 2