Elcometer 136 - Determining the Voltage Limits; The Lower Limit

Figure 5
Breakdown Voltage Against Thickness for Materials of
Different Dielectric Strengths
5.2 Determining the Voltage Limits.
5.2.1 The Lower Limit.
The lower voltage limit for effective operation is the dielectric
strength of air (1.3 to 4kV/mm) multiplied by the thickness.
If the coating thickness can be determined, read the lower
limit value from Figure 5, using the line marked AIR. For
instance, if the coating thickness is 1.0mm then the lower limit
is ~ 4.5kV.
If the coating thickness cannot be determined then the
minimum value has to be established experimentally.
Turn the ‘Voltage’ to zero and place the probe over an
uncoated area of substrate at the normal height of the coating
surface.
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