EEC Safety Testers Completes IEC 60601 Medical Testing

As the COVID-19 on-going pandemics continue affecting human lives. With rapidly raised on the confirmed cases and hospitalized many more every day. Medical staff relies on the data coming from the healthcare equipment. Having an inadequate performance may put higher risks for these patients. It may lead to hypoxic brain injury or possible deaths as of result. According to ECRI Institute 2019 Top 10 Health Technology Hazards^[1] report, Circuit Disconnection Ventilators, Physiologic Monitor System Failure, Cleaning Fluid Seeping into Electrical Components and, Flawed Battery Charging Systems are few nominated ones. Further, these are the key equipment used in this pandemic. In the previous article, we mentioned that healthcare equipment is unlike any other electronic equipment. As they used by both the operator and on patients. It has stringent testing regulations on products, especially on touch current. In this article, we will dive deeper and explain further in detail on leakage current testing.

Deeper Understanding in Leakage Current

Many of electronics standard requires to perform touch current testing. Table 1 illustrate various standards testing conditions from different industry. In brief, many of them derived from IEC 60990 methods of measurement of touch current and protective conductor current. By the same token, different industries may reference each other's standards as their benchmarks. At most, the current cannot exceed 10mA. In the last newsletter, 10mA is the let-go current threshold value.

Table 1. Leakage Current / Touch Current testing condition in some standards.

IEC 60990 set out the MDs based on and segmented by the human body’s physiological effect. Figure 1 shows the measuring network from min to max touch current weighted which is perception to unweighted (beyond let-go).

Figure 1. Measuring network from perception or reaction, to let-go and beyond.

Credit IEC 60990 standard.

Medical Leakage Current Test Model

In IEC 60601 standard, it listed out six leakage current test models. Figure 2 shows each criterion and detailed explanation. Further, with years of working with many international leading test labs and medical equipment firms. EEC has designed its own MDs to respond to each testing criterion.

Figure 2. IEC 60601 standard leakage current test models overview and EEC’s ESA series and 7630 series’ MD are designed to respond to each.

On high-level speaking, EEC has categorized it into three types of leakage current. There is earth leakage current (Ground-Line), surface leakage current (Probe High-Line), and surface to surface current (Probe High-Probe Low). Detail definition below;

Image A: Earth Leakage Current

Earth leakage current:

Earth leakage current measures the current that flows through a protective grounding wire through MD (human) to the ground. Class-II equipment does not need the measurement of earth leakage current as it has no protective grounding wire or path. Vice versa, Class I Product always need to performance Earth Leakage current test.

Image B: Type of surface leakage current, where leakage current flowing from the enclosure to earth or to another part of the enclosure (left). Surface leakage current for Class II product needs to comply with this test.

Image C. In IEC 60601, Surface leakage current including to Patient leakage. Current flowing from the patient connections via the patient to earth (left). The unintended appearance of a voltage from an external source on the patient and flowing from the patient via the patient connections of an F-TYPE applied part to earth (right).                                                                                             

Surface leakage current:

Surface leakage current measures the current that flows through a person who touches an ungrounded enclosed section of equipment. Image B and C are types of surface leakage currents.

Image D. Surface to surface leakage current. The patient auxiliary current flowing in the patient under normal use between any patient connection and all other patient connections and not intended to produce a physiological effect (left). The current flowing from the applied part of the external source via the patient to F type (right).

Surface to surface leakage current:

Under the normal or the single failure condition. It measures the current from some part of the equipment (eg. metal) flows from the human body to another part of the equipment. This current limitation is decided by the equipment electric circuit.

In summary, Table 2 illustrates IEC 60601 standard and testing type, also EEC’s corresponding definition.

Table 2. IEC60601 standard, testing type and EEC definition on connectivity.

Why EEC leakage current testing?

As the leakage current testing in medical standards is complex, which designs for ultimate safety. Most EEC medical customers utilizes  ESA series and 7630 touch current tester. For its complete and up-to-date MDs. Controlled by an intuitive testing operation that optimizes overall testing efficiency. Figure 3 illustrates ESA series MDs under different standards.

Figure 3. EEC ESA Series Measuring Device (MD) manual and circuits according to with the latest industry standards. Also, for medical equipment testing. It is common to perform up to 70 items of leakage current. ESA Series is capable setting up to 10,000 testing steps.

Medical equipment like other technology is not perfect, as it imposes some level of technology hazards. Thus, it requires strict tested and examined to minimize any possible faults. Extech Electronics Co. (EEC) has over 40 years of experience. We have worked with many international leading test labs and medical equipment firms. On ensuring the quality of their product delivered to their frontline customers. Now, where medical firms are rushing on their production to fight against this COVID-19 pandemic. We must put in place the quality of production with no-compromising attitude. Deliver safer equipment for both medical staff and patients.

[1] https://elautoclave.files.wordpress.com/2019/01/2019-top-10-hazards.pdf