Monroe Electronics Charge Plate - Analyzer - model 268A User Manual
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The ESD Association Standard Test Method STM3.1 recognizes that a small
amount of self decay may be unavoidable. This test method allows a maximum
self-decay rate of 10% in five minutes. Self decay shortens decay time
measurements. A small amount of self decay doesn’t impact a CPM decay
measurement enough to matter. Higher self-decay rates present an error in
decay time measurements that may be significant to your evaluations of ionizers.
Minimizing Plate Self Decay
Relative humidity becomes a problem when it rises above 60%. Keeping your
CPM clean and storing it in a warm, dry area are the most effective ways to
manage plate self decay. The warm air lowers the relative humidity.
When the CPM is stored in areas with higher humidity, use a heat gun to warm
the insulative supports and drive out any moisture that has been absorbed by
those supports. This will offer a temporary solution if the relative humidity and
plate self-decay rate are too high.
When this method seems to ineffective, clean the supports with a solution of de-
ionized water and isopropyl alcohol and allow the plate to dry for 24 hours.
Another Solution
Monroe Electronics’ newer CPM, Model 288, uses a high-voltage follower
(electrometer) technology that is much more resistant to the effects of high
humidity. We recommend this model for high-humidity areas where CPM
measurements are made.