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A Technical Presentation of the Factors
Affecting the Accuracy of
Carbon/Oxygen Probes

R. N. Blumenthal
Furnace Control Corp., Brookfield, Wisconsin

Reprinted from
1995 CARBURIZING AND NITRIDING WITH ATMOSPHERES
Proceedings of the
Second International Conference on
  Carburizing and Nitriding with Atmospheres
6-8 December 1995
Cleveland, Ohio

Abstract:

Although carbon/oxygen probes have been used extensively to measure the carbon potential of heat treating atmospheres for the last 20 years; there has not been any detailed technical explanation to describe the sources of errors that cause inaccurate measurements. The objective of this paper is to provide an in depth technical discussion of the factors affecting the accuracy of carbon/oxygen probes. The thermodynamic and kinetic principles governing the gas reactions that occur in a heat treating atmosphere will be employed to explain the errors that can occur in the relationship between the carbon potential and the measured voltage output of a carbon/oxygen probe. Test results comparing probes with different designs will be used to demonstrate the source of probe errors. Also a simple experimental procedure that determines the accuracy of a carbon/oxygen probe will be discussed. The application of the principles and procedures in this paper can be used for 1) more effective diagnosis of probe problems and 2) to improve the quality control of the carbon potential in heat treating atmospheres.

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Carrier gas CO content:
Key to quality in carburizing

   R. N. Blumenthal
Furnace Control Corp., Brookfield, Wisconsin

Reprinted from
Advanced Materials Processes
Volume 146, Number 1, July 1994

For a Free Reprint Call Furnace Control Corp. at (414) 462-7575

Check Out Carbon Control System Step by Step
Here's how a Wisconsin heat treater uses a simple procedure
to determine the accuracy of its carbon/ oxygen sensor
for tighter quality control.

Robert N. Blumenthal
Furnace Control Corp., Brookfield, Wisconsin
and
Richard Hlasny
Treat All Metals Inc., Milwaukee, Wisconsin

Reprinted from the
August 1991 issue of Heat Treating

For a Free Reprint Call Furnace Control Corp. at (414) 462-7575

Control of Endothermic Generators-
A Technical Comparison of
Endothermic and Nitrogen/
Methanol Carrier Atmosphere

R. N. Blumenthal
Furnace Control Corp., Brookfield, Wisconsin

Reprinted from
Heat Treating
Proceedings of the
16th ASM Heat Treating Society Conference & Exposition,
19-21 March 1996 Cincinnati, Ohio

Abstract: Control of endothermic generation will be discussed. Endothermic and nitrogen/methanol carrier atmospheres will also be compared. The comparisons will be based on a technical discussion which will include a summary of the concept of carbon potential, effect of carbon monoxide content on carbon potential, stability of carbon monoxide content of carrier gases, and kinetic considerations that affect surface carbon content and carbon control.

For a Free Reprint Call Furnace Control Corp. at (414) 462-7575

Zirconia Oxygen Probe,
Sooting and Air Burn
Out Considerations

R. N. Blumenthal, A. T. Melville
Furnace Control Corp., Brookfield, Wisconsin

Reprinted from
Heat Treating
Proceedings of the
16th ASM Heat Treating Society Conference & Exposition,
19-21 March 1996 Cincinnati, Ohio

Abstract: Carbon/oxygen probes have been used extensively to measure the carbon potential of heat treating atmospheres for the last 20 years. One of the most frequently encountered problems with the accuracy of an carbon/oxygen probe has been the formation of carbon "soot" on the probe. An in depth technical discussion of the relationship between probe design, accuracy and soot formation on the probe will be presented. Basic thermodynamic and kinetic principles will be utilized to explain how a catalytic reaction between the enriching gas, carrier atmosphere and the probe electrodes forms soot. The solution to the "sooting" problem utilizing a unique probe design will also be presented.

For a Free Reprint Call Furnace Control Corp. at (414) 462-7575