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. With an outline identical to modern miniature electrochemical cells, they are ideal for portable instruments. The series offers sensors capable of detecting most combustible gases, vapors, and ammonia at LEL levels, as well as gases with thermal conductivities different from air at % volume concentrations. Variants are available with enhanced stability and temperature performance testing for mining compliance. The sensors are poison-resistant to silicones and hydrogen sulfide, shock-resistant, and certified for hazardous environments.

Product Attributes

• Brand: SGX Sensortech
• Series: VQ500 Series
• Certifications: ATEX, IECEx, CSA, UL recognised
• Body Material: Stainless Steel
• Poison Resistance: Silicones and Hydrogen Sulfide
• Operating Principle: Catalytic oxidation and thermal conductivity
• Certifications: ATEX (II 2G Ex db IIC Gb, I M2 Ex db I Mb), IECEx (Ex db IIC Gb, Ex db I Mb), CSA (Component certification for Explosion Proof Enclosure Class I hazardous locations, UL 1203), UL (Component for intrinsically safe apparatus Class 1, Division 1, Groups A, B, C, D)

Technical Specifications

Specification	Details
Mechanical Dimensions	See outline, page 3
Body Material	Stainless Steel
Weight	22g
Environmental Temperature Range (Operation & Storage)	-40 to +55 C
Environmental Humidity Range (Operation & Storage)	0 to 80% (non-condensing)
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 60% LEL
Performance Linearity (Thermal Conductivity)	Refer to Pellistor Application Note 5
Response Time (T90)	< 20 seconds
Long Term Zero Drift (ZD-S Variants)	<5% LEL / month (based upon a 1 month period)
Long Term Zero Drift (All other Types)	<5% LEL / month (based upon a 12 month period)
Long Term Sensitivity Drift (ZD-S Variants)	<5% Full-Scale / month (based upon a 1 month period)
Long Term Sensitivity Drift (All other Types)	<5% Full-Scale / month (based upon a 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 (VQ546M, VQ546MR)	100% v/v
Maximum Gas Concentrations (VQ547TS, VQ548, VQ549)	100% LEL
Product Variants	VQ546M 4.25 0.1 V, 5060 mA, -4.0 (1% Methane) 15 mV, Not Required, A, No, No VQ546MR 4.25 0.1 V, 5060 mA, +4.0 (1% Methane) 15 mV, Not Required, A, No, No VQ547TS 3.0 0.1 V, 4050 mA, 21 (1.5% Ammonia) 30 mV, Some, A, No, No VQ548ZD 3.0 0.1 V, 6780 mA, 20 (1% Methane) 20 mV, Silicones & H2S, B, No, No VQ548ZD/W 3.0 0.1 V, 6780 mA, 20 (1% Methane) 20 mV, Silicones & H2S, B, Yes, No VQ548ZD-S 3.0 0.1 V, 6780 mA, 20 (1% Methane) 20 mV, Silicones & H2S, B, No, Yes VQ549ZD 4.25 0.1 V, 5060 mA, 30 (1% Methane) 20 mV, Silicones & H2S, B, No, No VQ549ZD/W 4.25 0.1 V, 5060 mA, 30 (1% Methane) 20 mV, Silicones & H2S, B, Yes, No
Product Marking (ATEX)	II 2G Ex db IIC Gb, I M2 Ex db I Mb Ta -40C to +55C, Pi: 2.5 W
Product Marking (IECEx)	Ex db IIC Gb, Ex db I Mb Ta -40C to +55C, Pi: 2.5 W
Hazardous Area Installation Instructions	Component approved only, requires further protection. Use with intrinsically safe supply (max Po 2.5 W). Max temperature rise on external surface 64 C. For Group I applications, withstand impact energy > 7 J. Not assessed as a safety device. No user-serviceable parts. Ambient temperature range: -40C to +55C.