Model HF-15B High Frequency Spark Tester
HF-15B Instruction Manual – Page 10
Electrical Shock Hazard from Production Line Spark Testers
By Henry H. Clinton
The commonly accepted maximum values of 60Hz. current passing through the
human adult body which permit a subject to let go of electrodes are nine
milliamperes for males and six milliamperes for females. At 3000 Hz. this value
increases to about 22 milliamperes for men and 15 milliamperes for women, DC
currents do not present the same let-go problems, but a subject can readily let
go at a level of 60 milliamperes. A continuous 60 Hz. current above 18
milliamperes stops breathing for the duration of the shock only. Ventricular
fibrillation may occur above a level of 67 milliamperes. The reaction current
level of 60 Hz. is about .5 milliamperes. Above this level a muscular reaction can
occur which can cause a secondary accident. The DC and 3 kHz. Levels are
probably considerably higher. Capacitor discharge energy of 50 Joules (watt-
seconds) is regarded as hazardous.
Clinton DC spark testers are current limited to 5 milliamperes or less. Three
kilohertz spark testers are limited to 4 milliamperes or less, and 60 Hz. types to
7 milliamperes. Impulse spark testers can deliver a maximum charge of about .2
Joules 248 times per second. All these spark testers have current outputs above
the reaction level, but none above the let-go threshold level. Because of the
possibility of secondary accidents caused by muscular reactions, operators
should be protected against accidental shock. Electrodes are supplied with
interlock switches, and these should not be disabled. The conductor under test
should be grounded. If an operator must inspect the product by touching its
surface while it is being spark tested, he should be electrically insulated from his
environment, and any possible cause of a secondary accident caused by reaction
should be eliminated.
For references, see: Dalziel, Ogden, Abbot, “Effect of Frequency on Let-Go
Currents,” Transactions of A.I.E.E., Volume 62, December 1943, and Dalziel,
“Electric Shock Hazard,” I.E.E.E., Spectrum, February 1972.
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