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Gas Analyzers


Models 7000, 7010

Models 7000, 7010


The continuous thermal conductivity analyzer has wide application in industry where it is desirable to analyze a two gas mixture. The thermal conductivity method is very stable in regards to span and zero drift. Applications include welding shield gas mixtures, food packaging mixtures, leak detection mixtures and heat treating atmospheres.


  • Rugged Thermco TC detector cell
  • User programmable ranges with automatic linearization (digital models)
  • Built-in flow controls
  • Choice of panel or wall mount style

Principles of Operation

Each gas has the ability to conduct heat at a specific rate. This is known as the thermal conductivity of the gas. This property is utilized in the Thermco thermal conductivity detector. Heated metal filaments are exposed to the zero and sample gases. The amount of heat carried away by the gases changes the rate of cooling of the wire filament and, therefore its temperature. This temperature change causes a resistance change. Since the filaments are arranged in a Wheatstone bridge, the resistance change can be converted to an electrical current that is available as an output signal.

The digital versions of the analyzer contain a linearizer which allows for a digital readout and a 4-20 mA signal output.

Common Mixtures Measured

Range Mixture Example Application
0-50% CO2 in Ar 5% CO2 in Ar
25% CO2 in Ar
MIG Shield Gas
0-10% O2 in Ar 5% O2 in Ar MIG Shield Gas
0-100% He in Ar 75% He in Ar MIG Shield Gas
0-50% CO2 in N2 30% CO2 in Ar Food Packaging
0-100% O2 in CO2 80% O2 in CO2 Food Packaging
0-20% H2 in N2 10% H2 in N2 Furnace Atmosphere
0-100% H2 in N2 75% H2 in N2 Furnace Atmosphere
0-50% N2 in Ar 8% N2 in Ar
20% N2 in Ar
Lamp Filling
0-50% He in N2 25% He in N2 Leak Detection



Many ranges are available. See above for common ranges. Consult the Thermco sales engineer for details.


  • ±0.3% of minor component absolute over range of 0-10%, all ranges.
  • ±0.5% of minor component absolute over a range of 10.1% to 30.0% all ranges.
  • ±1.0% of minor component absolute over a range of 30.1% to 60.0% all ranges.
  • ±2.0% of minor component absolute over a range of 60.1% to 100.0% all ranges except CO2 in Ar, which has an accuracy of ±8%

Example: For a 25% CO2 in Ar mixture, the analysis will be between 24.5 and 25.5% CO2.

This accuracy is valid over a temperature range of 50° to 90°F (10° to 32°C).



Response Time:

95% in 45 seconds for typical gas mixtures

Maximum Drift:

Zero, ±2% of full range per week; span, ±1% of full range per month. This applies to typical ranges.

Frequency of Calibration:

Calibration is recommended once per year when used under typical conditions.

Ambient Temperature Limits:

-10°F to 110°F (-23°C to 43°C).

Utilities Required:

Reference gas: The background gas in the mixture is required to flow continuously at 0.5 SCFH. This should be a clean, dry, oil free gas. Gas pressure required is 1-150 PSIG.

Sample gas: The sample gas is required to flow continuously at 1.0 SCFH. This should be a clean, dry, oil free gas. Gas pressure required is 1-150 PSIG, except gases containing H2 are 1-50 PSIG.

Power: 104-126 VAC, 50/60 Hz. 1 ampere standard; 204-240 VAC, 50/60 Hz. optional

Output Signal:

4-20 mA, proportional to gas analysis range selected. This output is isolated and self-powered with a compliance of 10 VDC. This output is not available on the analog meter versions.

Alarm Relays:

2 independent alarm relays, form C, with a rating of 5 amperes@120/240 VAC or 28 VDC (resistive). Alarms are not available on analog models. Note: When the alarm package is specified these alarm relays are utilized in the alarm package circuitry.


Model 7000: General purpose indoor panel mount. Model 7010: NEMA 4 wall mount.

Cell/Filament Material

Tungsten filaments with brass block and gold plated filament holder.

Weight and Dimensions:

Model Height Width Depth Weight
7000 15.5" (39.4cm) 13.6" (34.5 cm) 10.3" (26.2 cm) 44 lbs.(20 Kg)
7010 15.5" (39.4cm) 13" (33 cm) 10.3" (26.2 cm) 44 lbs.(20 Kg)

User Programmable Ranges

Linearization data for 6 standard ranges are built into the digital analyzers. These are 0-100% CO2 in Ar, 0-100% O2 in Ar, 0-100% He in Ar, 0-100% H2 in Ar, 0-100% CO2 in N2, 0-100% H2 in N2. The user may reprogram the analyzer to any of these ranges, except non-H2 ranges can not be converted to H2 ranges. Single point recalibration will be required after a range change. The analyzer will be factory calibrated for the range selected. A custom range is available for binary gas mixtures not listed above. Data for the custom range may be programmed into the analyzer by the factory or the user.


Thermco has been manufacturing thermal conductivity gas analyzers since the establishment of Thermco in 1951. The complete process of manufacturing, starting with the production of the cell filaments, is performed at our factory in LaPorte, Indiana, U.S.A. Each step of the manufacturing process is planned to produce an analyzer that is rugged and highly accurate. Thermco detector cells are designed not to “burnout” under conditions where there is no gas flow through the cell. Analyzers which have been functioning for over 20 years without replacement of any major parts is common.


Improper use of this product can cause serious injury or property damage. Personnel dealing with this equipment should read and understand warning labels and instruction manuals provided by Thermco.

Notice Concerning Supply Systems

In the interest of continued product development, Thermco reserves the right to change design features without prior notice. Sale of this equipment is under the terms of the Thermco warranty available upon request.

Ordering Information

Thermco gas analyzers are available through many local industrial gas suppliers. They may also be ordered directly from the factory. To get a quote, click here. It is specially important to order the correct pressure conditions for the application. If there are questions, please contact the Thermco sales engineer.