Ground-Resistance Testing

User Experience Network™ [Health Devices Feb 1993;22(2):96]


We have an external compression pump that has a three-prong power plug with the ground wire connected to the chassis, which is entirely covered in plastic. No metal parts are exposed, leaving no way to make a ground-resistance measurement. How should we handle electrical safety testing during inspection and preventive maintenance (IPM) procedures?


The inability to do a chassis-to-ground resistance test does not make the device unsafe. The device you described would seem to be intrinsically safer than the manufacturer's previous design, which included a metal outer chassis. The device also has no conductive parts that would be applied to the patient.

When no metal parts are exposed, you do not need to be concerned with chassis-to-ground resistance measurements. And while a ground-cord resistance measurement is not easy to do, the risk of electric shock (macro or micro) is lower with no exposed metal parts. The more important test for the compression unit is that the machine is applying the appropriate pressures and volumes of air, as specified by the manufacturer. Routine inspections should closely examine the integrity of the device and its accessories (e.g., look for cracks in the plastic covering, ensure that the air hoses do not show signs of excessive wear or are not crimped).

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