Instrument malfunction handling

Situations where re-testing is indicated (FDA 2006) include identified instrument malfunctions or sample handling problems, e.g. a dilution error. A re-testing plan... 

Critical Equipment Equipment, instrumentation, controls, or systems whose malfunction or failure would likely result in a catastrophic release of highly hazardous chemicals, or whose proper operation is required to mitigate the consequences of such release. (Examples are most safety systems, such as area LEL monitors, fire protection systems such as deluge or underground systems, and key operational equipment usually handling high pressures or large volumes.)... 

Electrical equipment and connections should not be handled with wet hands, nor should electrical equipment be used after liquid has been spilled on it. The equipment must be turned off immediately and dried thoroughly a fan or hair dryer will speed up the drying process. In case of a wet or malfunctioning electrical instrument that is used by several people, the plug should be pulled and a note cautioning co-workers against use should be left on the instrument... 

Standard deviation error of the signal from a nuclear channel gives a handle to determine the performance of the channel. In practice, nuclear detection phenomena have statistical fluctuations arovmd their mean value [6]. The measuring instrumentation also introduces additional error due to the electronic noise. In case of some malfunction in any part of the channel (from the nuclear detector to the output stage), the standard deviation of the channel signal will exceed the nuclear error by a wide margin. Also a zero value of signal mean and standard deviation would indicate an open connection somewhere in the channel circuit. 

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