VQ22 Combustible Gas Detector Elements To be read in conjunction withIntroduction to Pellistor Gas MARKING Sensor and Pellistor Application Notes 1, 2, 3, 4, 6 and 7. Each element is identified by a unique serial number written on the can of both the detector and compensator. The serial INTRODUCTION number is written in red on the detector and black on the The VQ22 is an improved poison-resistant sensor consisting of compensator. In addition, the detector carries a red circular two matched elements which are used for the detection of label on the base identifying the device type. combustible gases, particularly methane in air mixtures in concentrations from 0.1% upwards. There is no interference NOTES from water vapour or carbon dioxide. Using the recommended 1. Operation may be under either direct flow or diffusion bridge circuit below and the mounting arrangement shown on conditions in appropriate mountings (see page 3). page 3, the minimum sensitivity is 10 mV/% methane. 2. With open-circuit conditions at the bridge output. The VQ22 has been designed for use in atmospheres where 3. The response time is a function of the type of mounting traces of silicone and other poisoning agents may be present. used. 4. If the VQ22 is exposed to greater than 5% methane GENERAL DATA concentration, the calibration of the instrument should be Electrical checked. The information given below relates to the VQ22 operating in 5. The elements are supplied as a matched pair with a the recommended circuit shown. trimming resistor R of the correct value which is supplied Operation (see note 1) ......... continuous where necessary. The trimming resistor is to be connected Bridge supply ........... 2.0+ 0.1 V across the compensator element as shown below. Bridge power consumption ....... 0.48 W max 6. The resistance to poisoning by silicone compounds is partly Typical average sensor current..... 175 mA dependent upon the type of housing within which the Minimum sensitivity (see note 2) . 10 mV/% methane elements are mounted. Linearity ......... linear up to 5% methane 7. The response to certain of the heavy flammable vapours, 1 1 Response time to register 1 /%ina2 / % 4 2 especially aromatic substances with side chains, may be concentration (see notes 2 and 3) .... 2 seconds lower than that calculated from the conversion (K) factors Maximum methane concentration listed in the preamble. (see note 4) ........... 5 % Mechanical Mounting.............. see page 3 Outline............... see page 2 BRIDGECIRCUIT COMPENSATOR 2309C (BLACK SLEEVE) SEE R NOTE 5 27O 1kO 2V ZERO SET 27O DETECTOR (RED SLEEVE) OUTPUT SGX Sensortech(IS) Ltd Registered in England No.08067077 A1A-VQ22 Issue 5, March 2007TYPICAL RESPONSEOFVQ22TO20%L.E.L.OFVARIOUS GASES ANDVAPOURS (RELATIVE TOMETHANE) ASTHEBRIDGE SUPPLY VOLTAGE ISVARIED 100 5519A Methane 80 60 40 Propane n-Hexane 20 n-Octane 0 1.0 1.4 2.2 1.8 2.6 3.0 BRIDGE SUPPLY VOLTAGE (V) OUTLINE (Alldimensions without limits arenominal) 2311B Ref Millimetres F D A 11.05+ 0.25 E 1B B 6.10+ 0.25 C 3.56+ 0.13 C D 63.50 min E 1.02 1G F 7.37+ 0.51 1A G 8.20 max H 9.53 J 1.52 J O-RING METAL INSULATOR FLANGE H SEE NOTE Note No bends may be made in this length. SGX Sensortech(IS) Ltd Registered in England No.08067077 A1A-VQ22 Issue 5, March 2007 RELATIVE RESPONSE TO METHANE (%)