Effect of Measurement and Instrumentation Error On Potential Readings

AUTHORS

Frank J. Ansuini
Electrochemical Devices, Inc.

James R. Dimond
Dimondale Co., Inc.

ABSTRACT

Among the tools most widely used by a corrosion engineer or technician are a reference electrode and a voltmeter. With them, corrosion potential measurements can be made to assist in determining corrosion of a structure or the effectiveness of a cathodic protection system. However, there are sources of error in these measurements. This paper will discuss some of the more common sources of error and how to reduce them as much as practical.

Paper No. 01294 presented at Corrosion 2001, March 11 &45; 16, 2001, Houston, Texas
Published by NACE International, Houston, TX www.nace.org © NACE, 2005

Jim Dimond is President of Dimondale Co., Inc which designs and manufactures cathodic protection products. He has over 30 years experience in cathodic protection including product design, manufacturing and field engineering. Jim may be contacted at PO Box 838, Middlefield, OH 44062 or

CONCLUSIONS

Common sources of error in potential measurements include measurement circuit IR drop, external IR drop, and problems with the reference electrode. Corrosion control practitioners should understand the possible sources of these errors and use this understanding to reduce them as much as practical.

Standard digital multimeters with a 10 meg-ohm input impedance are not suitable for making error-free measurements in high resistivity electrolytes such as dry soil or concrete. In these applications, one should use either a very high input impedance meter designed for corrosion measurements or a potentiometric voltmeter.

Frank Ansuini is Technical Director of EDI which specializes in the development and marketing of corrosion control products. He has over 30 years experience in research and product development in corrosion. Frank may be contacted at PO Box 31, Albion, RI 02802 or

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