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

Current through June 25, 2024
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.