What are the advantages and disadvantages of utilising prods for magnetic particle inspections?

Prods induce a circular magnetic field by sending a high amperage (1000A typically) current through the testpiece. The high amperage can cause arcing between the electrodes and test surface. Contact points must be carefully cleaned, and electrode materials chosen to prevent contamination of the testpiece.

Advantages	Disadvantages
Variable field strength	Danger of arcing
AC or DC fields	Danger of overheating
Useful in confined spaces	Heavy transformer required
Low voltages	Possible to switch on without creating field
No poles to attract particles	Possible contamination of the testpiece by the electrode
Control of amperage	Must have good electrical contact
	Usually two-man operation

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