Mississippi Administrative Code
Title 11 - Mississippi Department of Environmental Quality
Part 5 - Underground Storage Tank Regulations
Chapter 2 - Mississippi Commission on Environmental Quality Underground Storage Tanks Regulations Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage Tanks (UST) (Adopted March 22, 1989; Amended August 25, 2011, Last Amended August 23, 2018)
Appendix 11-5-2-280.1 - GUIDELINES FOR THE EVALUATION OF UNDERGROUND STORAGE TANK CATHODIC PROTECTION SYSTEMS
Section 11-5-2-280.1-6 - CATHODIC PROTECTION TESTING
Section 11-5-2-280.1-6.1 - Equipment
Section 11-5-2-280.1-6.1.1 - Voltmeter/Ammeter
A good quality voltmeter/ammeter (multimeter) that has an adequate degree of accuracy is essential for testing cathodic protection due to the low voltage/current involved. Most "low end" voltmeters/ammeters are not capable of achieving results accurate enough to ensure reliable results and should therefore not be used.
All testing of cathodic protection systems must be accomplished with a high internal resistance (impedance of 10 meg-ohms or greater) voltmeter that is properly maintained and periodically calibrated in accordance with the manufacturer's recommendations. The voltmeter should be calibrated at least on an annual basis. It is important that the voltmeter has a high internal resistance in order to avoid introducing a large error when measuring structure-to-soil potentials.
The voltmeter must have a high degree of sensitivity and must be placed in as low a scale as possible (normally the 2 volt DC scale works well) in order to accurately measure the small voltages associated with cathodic protection systems. All voltage measurements obtained should be recorded as millivolts (mV). For example, a reading of-1.23 volts should be recorded as -1230 mV; a reading of-.85 volts should be recorded as -850 mV.
Voltmeters that have a variable input resistance can be utilized to ensure that contact resistance between the reference electrode and the electrolyte has been evaluated as a source of error (voltage drop) in the observed structure-to-soil potential. This is accomplished by changing the input resistance and noting whether or not the voltage observed changes significantly. If no voltage change is observed when the input resistance is changed, it can be assumed that contact resistance is not causing an error in the structure-to-soil potential measurement.
An ammeter that has a very low internal resistance is necessary when testing impressed current systems in order to accurately determine the current output of the rectifier and/or individual circuits in the system. Generally, amperage should only be measured where calibrated measurement shunts are present. Alternatively, a "clamp-on" type ammeter may be utilized in those cases where shunts are not present.
The batteries in the portable multimeter must also be in good condition. Batteries that are in poor condition can cause unintended errors. If there is any question about the condition of the batteries in the multimeter, they must be replaced.
