Why are the leakage current limits for patient and operator different?

This may seem obvious for most, but some forget the importance of understanding the “intent” of the requirements. For some, it is a matter of simply referencing the leakage current tables.

By having a thorough understanding of the requirements allows an engineer to make engineering judgments or design decisions that could potentially save you time and money.

Let’s go back to the topic of patient and operator leakage currents.

In IEC 60601-1, operator protection against electric shock is referred to as, “MOOP” (Means of Operator Protection) and patient protection against electric shock is referred to as, “MOPP” (Means of Patient Protection).

With that in mind, if you are a designer of a medical device, you may identify that some parts of your medical device can only be touched by the operator and some parts by the patient. You would then illustrate these parts that can be contacted by the operator and patient via an isolation/insulation diagram.

The following are the “rationale” why the operator leakage current limits are greater than patient leakage current limits:

  1. The operator is considered healthy and has greater and faster reflex against electric shock
  2. A healthy operator is considered to have greater body resistance and therefore, limits the leakage current that may flow through the operator’s body

In contrast to the operator,

  • A patient that is medicated or sedated will obviously have slower or no reflex against electric shock
  • A patient will have lower body resistance typically, 1000 Ohms (1000 Ohms total impedance shunted with filtering capacitors for test simulation) as a result of medication and/or illness

#MDD #IEC60601 #ISO13485 #ISO14971 #Medicaldevicedirective #CEmarking#productsafety #productcertification #REACH #ROHS #CaliforniaProp65

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