"The current that flows from an enclosure or enclosure part (other than an applied part) that is accessible to an operator or patient during normal use to earth or other parts of the enclosure by means of an external conductive connection other than a protective grounding conductor." In the case of Class II internally powered equipment, since they do not have a protective grounding line, the leakage current of their entire enclosure is considered; however, in the case of Class I equipment, which has a portion of the enclosure that is not connected to earth, the contact current of this portion of the enclosure is assessed.
According to IEC60601-1 "Medical Electrical Equipment Part I: General Requirements for Safety" standard, the enclosure contact current also includes the patient leakage current as well as the patient leakage current of F type. Here refers to the application part to contact the patient, and the patient is grounded, if the application part of the existence of a potential difference to ground, there must be a current from the application of the components through the patient to ground (which is to exclude the functional current of the equipment therapeutic needs), this is the patient leakage current.
The current that flows from the patient through the F-type application part to ground as a result of the accidental presence in the patient of a voltage from an external power supply.
Surface to Surface Leakage Current
Leakage current between any two points of a device that are not connected to ground under normal or single fault conditions, where the current flows from one part of the device through the human body and then into another part of the device;
And in the case of a medical device, this includes patient leakage current. Auxiliary current ---- "The current that flows into a patient that is between parts of an application part during normal use." Here it refers to an applied part of a device that has more than one part, and when these parts are connected to a patient at the same time, if there is a potential between the parts, a current flows through the patient. This current, in turn, is not a current that is required for the physiologic therapeutic function of the device, such as the current flowing through the patient between the lead electrodes of an electrocardiograph. As part of the F-type isolation (floating) application, this means that when there are multiple devices in use on the patient at the same time, or other unforeseen circumstances occur that cause an external supply voltage to be present on the patient (as a single fault state), then a patient leakage current is also generated.