VQ22TB

VQ22 Combustible Gas Detector Elements To be read in conjunction with "Introduction to Pellistor Gas Sensors" and Pellistor Application Notes 1, 2, 3, 4, 6 and 7. MARKING Each element is identified by a unique serial number written on the can of both the detector and compensator. The serial number is written in red on the detector and black on the compensator. In addition, the detector carries a red circular label on the base identifying the device type. INTRODUCTION The VQ22 is an improved poison-resistant sensor consisting of two matched elements which are used for the detection of combustible gases, particularly methane in air mixtures in concentrations from 0.1% upwards. There is no interference from water vapour or carbon dioxide. Using the recommended bridge circuit below and the mounting arrangement shown on page 3, the minimum sensitivity is 10 mV/% methane. The VQ22 has been designed for use in atmospheres where traces of silicone and other poisoning agents may be present. NOTES 1. Operation may be under either direct flow or diffusion conditions in appropriate mountings (see page 3). 2. With open-circuit conditions at the bridge output. 3. The response time is a function of the type of mounting used. 4. If the VQ22 is exposed to greater than 5% methane concentration, the calibration of the instrument should be checked. 5. The elements are supplied as a matched pair with a trimming resistor R of the correct value which is supplied where necessary. The trimming resistor is to be connected across the compensator element as shown below. 6. The resistance to poisoning by silicone compounds is partly dependent upon the type of housing within which the elements are mounted. 7. The response to certain of the heavy flammable vapours, especially aromatic substances with side chains, may be lower than that calculated from the conversion (K) factors listed in the preamble. GENERAL DATA Electrical The information given below relates to the VQ22 operating in the recommended circuit shown. Operation (see note 1) . . . . . . . . . continuous Bridge supply . . . . . . . . . . . 2.0 + 0.1 V Bridge power consumption . . . . . . . 0.48 W max Typical average sensor current . . . . . 175 mA Minimum sensitivity (see note 2) . . . 10 mV/% methane Linearity . . . . . . . . . linear up to 5% methane Response time to register 1 1/4% in a 2 1/2% concentration (see notes 2 and 3) . . . . 2 seconds Maximum methane concentration (see note 4) . . . . . . . . . . . 5 % Mechanical Mounting . . . . . . . . . . . . . . see page 3 Outline . . . . . . . . . . . . . . . see page 2 BRIDGE CIRCUIT COMPENSATOR (BLACK SLEEVE) 2309C R 27O 2V SEE NOTE 5 1 kO ZERO SET 27O DETECTOR (RED SLEEVE) OUTPUT SGX Sensortech(IS) Ltd Registered in England No.08067077 A1A-VQ22 Issue 5, March 2007 TYPICAL RESPONSE OF VQ22 TO 20% L.E.L. OF VARIOUS GASES AND VAPOURS (RELATIVE TO METHANE) AS THE BRIDGE SUPPLY VOLTAGE IS VARIED 100 5519A Methane 80 RELATIVE RESPONSE TO METHANE (%) 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 (All dimensions without limits are nominal) 2311B E 1B Ref Millimetres A B C D E F G H J 11.05 + 0.25 6.10 + 0.25 3.56 + 0.13 63.50 min 1.02 7.37 + 0.51 8.20 max 9.53 1.52 F D C 1G 1A J O-RING INSULATOR METAL 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 RECOMMENDED MOUNTING ARRANGEMENTS 2310C AA LEAKPROOF JOINT AB 60 MESH STAINLESS STEEL GAUZE 1AD Ref Millimetres AA AB AC AD AE AF AG 19.05 max 9.53 + 0.13 8.33 + 0.13 8.20 min 19.05 max 9.53 + 0.13 8.20 min AC 3 FLOW RATE 500 cm /min AE AF FILTER PAPER AND 60 MESH STAINLESS STEEL GAUZE 1AG SGX Sensortech(IS) Ltd Registered in England No.08067077 A1A-VQ22 Issue 5, March 2007