Product Overview

The VQ500 Series is a range of miniature, fully certified, flameproof catalytic combustible gas sensor heads. Optimized for low power consumption, these sensors utilize a pellistor pair for detecting combustible gases and % volume gases via thermal conductivity. Their design is identical to modern miniature electrochemical cells, making them ideal for portable instruments. The series offers sensors capable of detecting most combustible gases and vapors, as well as ammonia at LEL levels. Thermal conductivity versions can detect gases with thermal conductivities different from air at % volume concentrations. Specific variants undergo temperature testing for mining performance compliance, and the VQ548ZD-S offers enhanced stability through extra burn-in.

Product Attributes

• Brand: SGX Sensortech
• Series: VQ500 Series
• Certifications: ATEX, IECEx, CSA, UL recognised
• Material: Stainless Steel (Enclosure, Mesh), Epoxy resin (Bushing)
• Poison Resistance: Silicones and Hydrogen Sulfide (specific variants)
• Body Size: Standard miniature
• Certifications: ATEX, IECEx, CSA, UL recognised

Technical Specifications

Specification	Details
Operating Principle	Catalytic oxidation on a heated pellistor bead, detected as a resistance change. A second inert bead compensates for ambient temperature variations.
Mechanical Dimensions	Refer to outline drawing (Page 3)
Body Material	Stainless Steel
Weight	22g
Environmental Operating & Storage Temperature Range	-40 to +55 C
Environmental Humidity Range (non-condensing)	0 to 80%
Electrical Supply Voltage	3.00 V to 4.25 V (Depending upon type)
Electrical Supply Power	135 mW to 230 mW (Depending upon type)
Performance Linearity	Catalytic: Linear up to 60%LEL; Thermal Conductivity: Refer to Pellistor Application Note 5
Response Time (T90)	< 20 seconds
Long Term Zero Drift (ZD-S Variants)	<5%LEL / month (1 month period)
Long Term Zero Drift (All other Types)	<5%LEL / month (12 month period)
Long Term Sensitivity Drift (ZD-S Variants)	<5% Full-Scale / month (1 month period)
Long Term Sensitivity Drift (All other Types)	<5% Full-Scale / month (12 month period)
Zero Offset with Temperature (ZD/W Variant Only)	0.2% methane variation between -10C to +40C (compared to 20C reading)
Warranty Period	12 months
Maximum Gas Concentrations (Note d)	VQ546M, VQ546MR: 100%v/v; VQ547TS, VQ548, VQ549: 100%LEL
Product Variants	Model Operating Voltage (V d.c) Sensor Current (mA) Minimum Sensitivity (mV/%Vol) Offset (mV) Poison Resistance Outline Routine Temp Tested Routine Burn-In & Drift Test VQ546M 4.25 0.1 50 60 -4.0 (1% Methane) 15 Not Required A No No VQ546MR 4.25 0.1 50 60 +4.0 (1% Methane) 15 Not Required A No No VQ547TS 3.0 0.1 40 50 21 (1.5% Ammonia) 30 Some A No No VQ548ZD 3.0 0.1 67 80 20 (1% Methane) 20 Silicones & H2S B No No VQ548ZD/W 3.0 0.1 67 80 20 (1% Methane) 20 Silicones & H2S B Yes No VQ548ZD-S 3.0 0.1 67 80 20 (1% Methane) 20 Silicones & H2S B No Yes VQ549ZD 4.25 0.1 50 60 30 (1% Methane) 20 Silicones & H2S B No No VQ549ZD/W 4.25 0.1 50 60 30 (1% Methane) 20 Silicones & H2S B Yes No
Certifications Details	ATEX: II 2G Ex db IIC Gb I M2 Ex db I Mb Ta -40C to +55C, Pi: 2.5 W (EC Type-Examination Certificate: Sira 01ATEX1073U) IECEx: Ex db IIC Gb Ex db I Mb Ta -40C to +55C, Pi: 2.5 W (IECEx Certificate: IECEx SIR 04.0014U) CSA: Component certification for Explosion Proof Enclosure, Class I hazardous locations (Standard C22.2 No. 30-M 1986, Certificate No. 2589677). Assessed to UL 1203 (4th Edition). UL: Component recognition for intrinsically safe apparatus, Class 1, Division 1, Groups A, B, C, D hazardous locations (UL 913, 7th edition, File E186043).
Hazardous Area Installation Instructions	Component approved only; requires further protection for standalone use in hazardous areas. Must be used with an intrinsically safe supply (max output Po 2.5 W). Maximum temperature rise on external surface does not exceed 64 C. For Group I applications, must withstand impact energy > 7 J. Not assessed as a safety device. No user-serviceable parts. Certification relies on Stainless steel enclosure/mesh and Epoxy resin bushing. Shall only be used in an ambient temperature range of -40C to +55C.

2304140030_Amphenol-VQ546MR_C1526427.pdf