Product Overview

The VQ35 series thermal conductivity gas detector elements are designed for detecting gases in 0 100% by volume concentrations. Utilizing the thermal conductivity principle, these devices consist of two matched elements: a sensing element exposed to the atmosphere under test and a reference element sealed in reference air. The response is based on the difference in thermal conductivity between the test atmosphere and reference air. The VQ35M features braided leads with a sealed compensator can, while the VQ35MB offers extended pins for direct PCB fitting with a sealed compensator can. For models with open compensator cans, the compensator must be mounted in a sealed chamber filled with air or nitrogen. These sensors are suitable for operation in direct flow or diffusion conditions and are intended to be read in conjunction with "Introduction to Pellistor Gas Sensors" and Pellistor Application Note 5 Thermal Conductivity Sensors.

Product Attributes

• Brand: SGX Sensortech
• Element Identification: Serial number in red (sensing), black (reference). Red circular label on sensing element base.

Technical Specifications

Specification	Value
Series	VQ35
Operation Principle	Thermal Conductivity
Concentration Range	0 100% by volume
Recommended Bridge Supply Voltage	4.25 V
Maximum Bridge Power Consumption	0.26 W
Response to Methane in Air (min)	1.0 mV/%
Maximum Sensing Element Operating Temperature	500 C (at recommended bridge supply voltage)
Mounting	See page 3 for arrangements
Lead Types	Braided (VQ35M), Extended pins for PCB (VQ35MB)
Compensator Can	Sealed (VQ35M, VQ35MB), Open (VQ35, VQ35B)
Model	VQ35
Model	VQ35B
Model	VQ35M
Model	VQ35MB
Outline VQ35M Dimension A (Nominal)	11.05 + 0.25 mm
Outline VQ35M Dimension B (Nominal)	6.10 + 0.25 mm
Outline VQ35M Dimension C (Nominal)	3.56 + 0.13 mm
Outline VQ35M Dimension D (Min)	63.5 mm
Outline VQ35M Dimension E (Nominal)	1.0 mm
Outline VQ35M Dimension G (Max)	8.2 mm
Outline VQ35M Dimension H (Nominal)	9.53 mm
Outline VQ35M Sensing Element (Nominal)	6.25 + 0.50 mm
Outline VQ35M Reference Element (Nominal)	7.75 + 0.38 mm
Outline VQ35MB Dimension A (Nominal)	11.05 + 0.25 mm
Outline VQ35MB Dimension B (Nominal)	6.10 + 0.25 mm
Outline VQ35MB Dimension C (Nominal)	3.56 + 0.13 mm
Outline VQ35MB Dimension D (Min)	40.0 mm
Outline VQ35MB Dimension E (Nominal)	1.0 mm
Outline VQ35MB Dimension G (Max)	8.2 mm
Outline VQ35MB Dimension H (Nominal)	1.5 mm
Outline VQ35MB Sensing Element (Nominal)	6.25 + 0.50 mm
Outline VQ35MB Reference Element (Nominal)	7.75 + 0.38 mm
Recommended Mounting Arrangement AA (Nominal)	9.53 + 0.13 mm
Recommended Mounting Arrangement AB (Nominal)	8.33 + 0.13 mm
Recommended Mounting Arrangement AC (Min)	8.20 mm
Recommended Mounting Arrangement AD (Nominal)	9.53 + 0.13 mm
Recommended Mounting Arrangement AE (Min)	8.20 mm
Thermal Conductivity of Gases (Relative to Air)	See table on page 2 of source document