Simulated Hand in EMC Standard_Century Wisdom (Suzhou) Testing Technology Co., Ltd

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Simulated Hand in EMC Standard

Release time:

2023-05-30 15:24

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A simulated hand, artificial a hand, is a device of electrical characteristics. In the electromagnetic compatibility test, the simulated hand is used for the conducted emission test, electric rapid pulse group and conducted immunity in the frequency range of 150kHz ~ 30 MHz (5MHz ~ 30 MHz is the most critical frequency) to simulate the influence of the operator's hand on the measurement..

In some product specifications, such as CISPR 14, IEC60601-1-2, it is required to use simulated hands for EUT that is not connected to the metal part of EUT and is hand-held during normal use. Metal-coated plastic housings may also use simulated hands. The types of devices that need to be evaluated with simulated hands are power tools, household appliances (e. g. hand blenders), phone grips, joysticks, keyboards, etc.

　　1, Simulate the structure of the hand and RC components

The simulated hand consists of a metal foil (strip) and an RC element.

The metal foil strip that simulates the effect of the user's hand touching the handle of the device or the body of the device is usually 60mm wide and is placed or wrapped around the part of the device that is usually touched by the user in a prescribed manner. For the keyboard, a metal foil or, more preferably, a metal plate with a maximum size of 100mm x 300mm may be used on top of the keyboard.

The RC element consists of a capacitor of C = 220pF ± 20% in series with a resistor of 510Ω ± 10%. The length of the connection line between the RC element and the metal foil should be 1m.

Fig.1 Simulated hand structure

If the whole interconnection line is regarded as a line in free space, when the upper limit frequency of the conduction emission test is 30MHz, the inductance L of the connection line should be less than 1.4 μH. For a given length of connecting line, the minimum diameter (m) of the outgoing line can be calculated from this requirement and the following formula:

In the formula:

m-dielectric constant, 4π × 10-7 H/m;

l-the length of the line, in meters (m);

d-the diameter of the line in meters (m).

Note: When the inductance meets the requirement of 1.4μH, the impedance of the RC network will dominate at 30MHz.

　　2, General principles of the use of simulated hands

The maximum length of the connection line between the RC element and the reference ground is usually not more than 1m. When the conducted emission of the power port is measured, the reference point is the reference ground of the AMN. When measuring the emission of a signal line or a control line, the reference point is the reference ground of.

General principles of using simulated hands:

1) The M end of the RC element should be connected to any exposed, non-rotating metal part of the EUT

2) All metal foil wound on fixed or detachable handles provided with the equipment.

3) Metal parts with coating or paint on the surface are considered as exposed metal parts and should be directly connected to RC elements.

　　3. The application of simulated hands in handheld household appliances and power tools:

a) If the equipment case is all metal and grounded, it is not necessary to use simulated hands.

B) If the housing of the equipment is made of insulating material, the metal foil should be wrapped around the handle B (as shown in Figures 2 and 3) and the second handle D (if any). A 60mm wide metal foil should also be wrapped around the body C (as shown in Figures 2 and 3) at the stator core of the motor, or on the transmission (if this can obtain a higher disturbance level). All of these metal foils (including also the metal ring or sleeve A where applicable) shall be connected together to the M terminal of the RC element.

Figure 2 Portable Electric Drill

Figure 3 Portable Chainsaw

c) If one part of the equipment housing is metal and the other part is insulating material and is an insulating handle, it should be wrapped with metal foil at the handles B and D [Figure 2)]. If the body at the motor is non-metallic, use a 60mm wide metal foil to wind the body C of the motor stator core; or wind it on the gear box (if it is an insulating load-bearing material and a larger disturbance level is measured). The metal part A of the body, the metal foil wrapped around the handles B and D, and the metal foil at the body C are connected and then connected to the terminal M of the RC element.

d) When Class II equipment (I. e. double insulation, no ground wire) has two insulated handles A and B and a metal body C, such as a chainsaw [Figure 3), the metal foil should be wrapped around handles A and B. The metal foil at A and B is connected to the metal body C and then connected to the M terminal of the RC element.

According to past experience, the impact of simulated hands on different products is not the same. For hair dryers, hair clips of this type of equipment impact is small, while the impact of electric drills, saws, angle grinding and other hand-held power tools is relatively large.

　　4. Application of simulated hands in information technology equipment:

4 and 5 give an example of an ITE device for a telephone handle and keypad. For telephone handles, a 60mm wide foil is wrapped around the handle with some overlap. For keyboards, the metal foil or printed circuit board should cover the entire key area as much as possible.

When using printed circuit boards, the metal side should be placed on the keyboard, but the size should not exceed 300mm x 100mm.

Fig. 4 Simulated Hand Applied to Phone Handle

Figure 5 Simulated hand applied to a typical keyboard

　　5, for medical equipment, simulated hand use:

ME equipment is widely used to simulate hands and may be used in conducted emissions, electrical fast transient bursts, and conducted immunity tests. In daily tests, Century Huize Laboratory found that the use and placement of simulated hands have a non-negligible impact on the test results of conducted emission, electrical fast transient burst and conducted immunity tests of medical electrical equipment. According to the experience of Century Huize, according to the IEC60601-1-2, the use of simulated hands should follow:

In the conducted emission test, simple electrical devices such as some dental drills can be tested according to CISPR14-1/GB4343.1; Information technology equipment connected to ME equipment or ME system can be tested according to CISPR11/GB/T9254.

When the test is specified in IEC60601-1-2/YY9706.102, ME equipment and ME system patient coupling components are terminated as specified below during the test. In any case, no decoupling device is used between the injection end and the patient coupling point:

-For patient coupling points that do not have conductive contact with the patient, terminate the analog hand and RC element specified in GB/T6113.102. The size and placement of the simulated hand metal foil simulates a similar area and location to be coupled to the patient in normal use. The metal foil simulating the hand is connected to the M end of the RC element, the other end of which is connected to the ground reference plane.

-For the patient coupling point that has conductive contact with the patient, the M end of the RC element (see GB/T6113.102) is directly connected to the patient coupling point, and the other end of the RC element is connected to the ground reference plane. If it is difficult to verify the proper operation of the ME equipment or ME system after the M is terminated to the coupling point, an insulating material with a maximum thickness of 5mm may be used between the metal foil simulating the hand (see GB/T6113.102) and the patient coupling point. At this point, the metal foil size and placement position of the simulated hand simulates a similar area and location of patient coupling in normal use. The M end of the RC element is connected to the metal foil and not to the patient coupling point, and the other end of the RC element is in any case connected to the ground reference plane.

-For ME devices and ME systems with multiple patient coupling points and intended to connect to a single patient, use the simulated hand specified above for each patient coupling point and each patient coupling component. The analog hand is connected to a common contact, and the common contact is connected to the M end of the RC element according to the provisions of GB/T6113.102. For ME equipment and ME systems intended to connect multiple patients, use simulated hands as specified above and use separate common contacts and RC elements for each patient to simulate the capacitive coupling effects and RF impedance of the patient. The other end of the RC element is in any case connected to the ground reference plane.

Figure 6. Multi-parameter patient monitor test layout

-If a patient physiology simulator is expected to simulate patient physiological signals, as well as patient capacitive coupling effects and patient RF impedance, the patient physiology simulator shall provide an impedance equivalent to the simulated hand and RC element specified above between the coupling point and the ground reference plane.

In addition to the patient coupling cable being tested as specified above, the hand-held ME equipment and the parts of the ME equipment that are expected to be hand-held in normal use are tested using a simulated hand as specified in GB/T6113.102, which is sized and positioned to simulate the area and position of the operator coupling in normal use. The metal foil of the simulated hand is connected to the M end of the RC element specified in GB/T6113.102, and the other end of the RC element is connected to the ground reference plane.

　　6, conclusion.

The simulated hand has a great influence on the conduction test, the electric fast pulse group and the conduction immunity, probably because the electromagnetic wave originally radiated to the space returns to the EUT through the RC element along the wire through the metal foil. Therefore, the standard use of the simulated hand is of great significance to the rigor and accuracy of the test. In actual use, some AMN and LISN have built-in RC components, and users only need to use wires to connect metal foils. Due to the limitation of the author's ability, there are inevitably some mistakes in the article. Welcome to discuss with us in the century.

References

　　IEC 60601-1-2: 2014 A1:2020 ED4.1

YY9706.102-2021

GB4343.1-2018

　　CISPR14-1:2020

　　GB/T6113.102：2018

　　CISPR16-1-2:2014

　　CISPR 32:2015 AMD1:2019

　　GB/T 9254.1-2021

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