IEC 62368-1 Test requirements for equipment containing audio amplifiers
2025-08-14
IEC 62368-1 Test requirements for equipment containing audio amplifiers
According to the ITU-R 468-4 (Measurement of audio noise levels in sound broadcasting) specification, the 1000Hz frequency response is 0dB (see the figure below), which is suitable as a reference level signal and is convenient for evaluating the frequency
response performance of audio amplifiers. Peak response frequency signal. If the manufacturer declares that the audio amplifier is not intended to operate under 1000Hz conditions, the audio signal source frequency should be replaced by the peak response frequency. The peak response frequency is the signal source frequency when the maximum output power is measured on the rated load impedance (hereinafter referred to as the speaker) within the intended operating range of the audio amplifier. In actual operation, the inspector can fix the signal source amplitude and then sweep the frequency to check that the signal source frequency corresponding to the maximum effective value voltage appearing on the speaker is the peak response frequency.
Output power type and regulation - maximum output power
The maximum output power is the maximum power that the speaker can obtain, and the corresponding voltage is the maximum effective value voltage. Common audio amplifiers often use OTL or OCL circuits based on the working principle of Class AB amplifiers. When a 1000Hz sine wave audio signal is input into the audio amplifier and enters the saturation region from the amplification region, the signal amplitude cannot continue to increase, the peak voltage point is limited, and flat-top distortion appears at the peak.
Using an oscilloscope to test the speaker's output waveform, you can find that when the signal is amplified to the effective value and cannot be further increased, peak distortion occurs (see Figure 2). At this time, it is considered that the maximum output power state has been reached. When peak distortion occurs, the crest factor of the output waveform will be lower than the sine wave crest factor of 1.414 (as shown in Figure 2, crest factor = peak voltage / effective value voltage = 8.00/5.82≈1.375＜1.414)
Figure 2: 1000Hz sine wave signal input condition, speaker output waveform at maximum output power
Output power type and adjustment - non-clipped output power,Non-clipped output power refers to the output power at the junction of the saturation zone and the amplification zone when the speaker is operating at maximum output power and without peak distortion (the operating point is biased towards the amplification zone). The audio output waveform presents a complete 1000Hz sine wave with no peak distortion or clipping, and its RMS voltage is also less than the RMS voltage at maximum output power (see Figure 3).
Figure 3 shows the output waveform of the speaker entering the non-clipping output power state after reducing the amplification factor (Figures 2 and 3 show the same audio amplifier network)
Because audio amplifiers operate at the interface between the amplification and saturation regions and are unstable, signal amplitude jitter (the upper and lower peaks may not be equal) can be generated. The crest factor can be calculated using 50% of the peak-to-peak voltage as the peak voltage. In Figure 3 , the peak voltage is 0.5 × 13.10V = 6.550V , and the RMS voltage is 4.632V . The crest factor = peak voltage / RMS voltage = 6.550 / 4.632 ≈ 1.414. Output Power Type and Regulation - Power Regulation Methods. Audio amplifiers receive small signal inputs, amplify them, and output them to the speakers. The gain ratio is typically adjusted using a detailed volume scale (for example, a television's volume adjustment can range from 30 to 100 steps). However, adjusting the gain ratio by adjusting the signal source amplitude is much less effective. Reducing the signal source amplitude, even with the amplifier's high gain, will still significantly reduce the speaker's output power (see Figure 4). In
Figure 4: Output waveform when the speaker enters a non-clipped output power state after reducing the signal source amplitude.
(Figures 2 and 4 show the same audio amplifier network)
Figure 3 , adjusting the volume returns the speaker from maximum output power to a non-clipping state, with an RMS voltage of 4.632V . In Figure 4 , by adjusting the signal source amplitude, the speaker is adjusted from the maximum output power state to the non-clipped output power state, and the effective value voltage is 4.066V . According to the power calculation formula
Output power = square of voltage RMS / speaker impedance
The non-clipped output power of Figure 3 exceeds that of Figure 4 by about 30%, so Figure 4 is not the true non-clipped output power state.
It can be seen that the correct way to call back from the maximum output power state to the non-clipping output power state is to fix the signal source amplitude and adjust the amplification factor of the audio amplifier, that is, to adjust the volume of the audio amplifier without changing the signal source amplitude.
Output power type and adjustment - 1/8 non-clipped output power
Normal operating conditions for audio amplifiers are designed to simulate the optimal operating conditions of real-world speakers. Although real-world sound characteristics vary greatly, the crest factor of most sounds is within 4 (see Figure 5).
Figure 5: A real-world sound waveform with a crest factor of 4
Taking the sound waveform in Figure 5 as an example, crest factor = peak voltage / RMS voltage = 3.490 / 0.8718 = 4. To achieve distortion-free target sound, an audio amplifier must ensure that its maximum peak is free of clipping. If a 1000Hz sine wave signal source is used as a reference, to ensure the waveform remains undistorted and the 3.490V peak voltage is not current-limited, the RMS signal voltage should be 3.490V / 1.414 = 2.468V. However, the RMS voltage of the target sound is only 0.8718V. Therefore, the reduction ratio of the target sound to the RMS voltage of the 1000Hz sine wave signal source is 0.8718 / 2.468 = 0.3532. According to the power calculation formula, the voltage RMS reduction ratio is 0.3532, which means that the output power reduction ratio is 0.3532 squared, which is approximately equal to 0.125=1/8.
Therefore, by adjusting the speaker output power to 1/8 of the non-clipped output power corresponding to the 1000Hz sine wave signal source, the target sound with no distortion and a crest factor of 4 can be output. In other words, 1/8 of the non-clipped output power corresponding to the 1000Hz sine wave signal source is the optimal working state for the audio amplifier to output the target sound with a crest factor of 4 without loss.
The operating state of the audio amplifier is based on the speaker providing 1/8 non-clipping output power. When in the non-clipping output power state, adjust the volume so that the effective value voltage drops to about 35.32%, which is 1/8 non-clipping output power. Because pink noise is more similar to real sound, after using a 1000Hz sine wave signal to obtain non-clipping output power, pink noise can be used as the signal source. When using pink noise as the signal source, it is necessary to install a bandpass filter as shown in the figure below to limit the noise bandwidth.
Normal and abnormal working conditions - normal working conditions
Different types of audio amplifier equipment should consider all of the following conditions when setting normal operating conditions:
- The audio amplifier output is connected to the most unfavorable rated load impedance, or the actual speaker (if provided);
——All audio amplifier channels work simultaneously;
- For an organ or similar instrument with a tone generator unit, instead of using a 1000 Hz sine wave signal, depress the two bass pedal keys (if any) and the ten manual keys in any combination. Activate all stops and buttons that increase the output power, and adjust the instrument to 1/8 of the maximum output power;
- If the intended function of the audio amplifier is determined by the phase difference between the two channels, the phase difference between the signals applied to the two channels is 90°;
For multi-channel audio amplifiers, if some channels cannot operate independently, connect the rated load impedance and adjust the output power to 1/8 of the amplifier's designed non-clipped output power.
If continuous operation is not possible, the audio amplifier operates at the maximum output power level that allows continuous operation.
Normal and abnormal working conditions - Abnormal working conditions
The abnormal working condition of the audio amplifier is to simulate the most unfavorable situation that may occur on the basis of normal working conditions. The speaker can be made to work at the most unfavorable point between zero and maximum output power by adjusting the volume, or by setting the speaker to short circuit, etc.
Normal and abnormal working conditions - temperature rise test placement
When conducting a temperature rise test on an audio amplifier, place it in the position specified by the manufacturer. If there is no special statement, place the device in a wooden test box with an open front, 5 cm from the front edge of the box, with 1 cm of free space along the sides or top, and 5 cm from the back of the device to the test box. The overall placement is similar to simulating a home TV cabinet.
Normal and abnormal working conditions - noise filtering and fundamental wave restoration The noise of some digital amplifier circuits will be transmitted to the speaker along with the audio signal, causing disordered noise to appear when the oscilloscope detects the speaker output waveform. It is recommended to use the simple signal filtering circuit shown in the figure below (the method of use is: points A and C are connected to the speaker output end, point B is connected to the audio amplifier reference ground/loop ground, and points D and E are connected to the oscilloscope detection end). This can filter out most of the noise and restore the 1000Hz sinusoidal fundamental wave to a large extent (1000F in the figure is a typo, it should be 1000pF).
Some audio amplifiers have superior performance and can solve the problem of peak distortion, so that the signal will not be distorted or clipped when it is adjusted to the maximum output power state. At this time, the non-clipping output power is equivalent to the maximum output power. When visible clipping cannot be established, the maximum output power can be regarded as the non-clipping output power.
Electric energy source classification and safety protection
Audio amplifiers can amplify and output high-voltage audio signals, so the audio signal energy source must be classified and protected. When classifying, be sure to set the tone controller to a balanced position, allowing the audio amplifier to operate at maximum non-clipped output power to the speaker. Then, remove the speaker and test the open-circuit voltage. The audio signal energy source classification and safety protection are shown in the table below.
Audio signal electrical energy source classification and safety protection
Energy source level
Audio signal RMS voltage (V)
Example of safety protection between energy source and general personnel
Example of safety guarding between energy source and instructed personnel
ES1
≤71
No safety protection required
No safety protection required
ES2
>71 and ≤120
Terminal insulation (accessible parts non-conductive):
Indicates ISO 7000 0434a code symbol or 0434b code symbol
No safety protection required
Terminals are not insulated (terminals are conductive or wires are exposed):
Mark with indicative safety precautions, such as "touching uninsulated terminals or wires may cause discomfort"
ES3
>120
Use connectors that comply with IEC 61984 and are marked with the 6042 coding symbols of IEC 60417
Pink Noise Generator
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Python-based medium-frequency electrotherapy measurement and analysis system makes testing more convenient
2025-08-12
Introduction
In the era of intelligent diagnosis and treatment of medical devices, have you encountered these problems?
The accuracy of output parameters of medium frequency therapy equipment is difficult to verify
The medical safety certification cycle is long, time-consuming and labor-intensive
To address the industry's pain points, traditional testing methods are unable to fully cover core indicators. We have launched a new generation of medium-frequency electrotherapy measurement and analysis system, using technology to provide "data insurance" for medical safety!
The medium-frequency electrotherapy measurement and analysis system is developed for testing medium-frequency electrotherapy devices. Based on the YY 9706.210-2021 Medical Electrical Equipment Part 2-10 and YY_T 0696-2021 Measurement Standards for Output Characteristics of Nerve and Muscle Stimulators, the measurement parameters emphasize six key indicators: effective value, current density, pulse energy, pulse width, frequency, and DC component. This provides key data support for the safety certification of medical devices.
Detailed Explanation of Technical Parameters
Effective value monitoring: 0-100mA high-precision measurement, error
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Analysis of the Infeasibility of GB 9706/IEC 60601 Oxygen-Enriched Spark Test in Market Testing
2025-08-05
Analysis of the Infeasibility of GB 9706/IEC 60601 Oxygen-Enriched Spark Test in Market Testing
Introduction
The GB 9706/IEC 60601 standard series guides the safety and performance of medical electrical devices, including numerous stringent testing requirements to ensure device safety under various conditions. Among these tests, the oxygen-enriched spark test specified in IEC 60601-1-11 is used to assess the fire risk of medical devices in oxygen-enriched environments. This test simulates the potential for ignition from an electric spark in a high-oxygen environment and is particularly important for devices such as ventilators or oxygen concentrators. However, implementing this test during market testing presents significant practical challenges, particularly when using copper pins derived from printed circuit board (PCB) copper-clad laminates. This article will explore why the oxygen-enriched spark test is impractical for market testing due to the complexity of copper pin sample preparation, particularly the inability of laboratories to reliably prepare copper pins from PCB copper-clad laminates. The article will also propose an alternative test method based on materials analysis.
Background: Oxygen-enriched spark testing in IEC 60601
The oxygen-enriched spark test assesses the ignition risk of medical devices in environments with oxygen concentrations above 25%. The test generates a controlled spark between two electrodes (typically copper pins) in an oxygen-enriched atmosphere to determine whether it ignites surrounding materials. The standard sets strict requirements for the test setup, including electrode material, spark gap, and ambient conditions.
Copper pins are often designated as electrodes due to their excellent conductivity and standardized properties. In market testing, where devices are evaluated for compliance after production, the test assumes that representative samples (such as copper pins that mimic the copper-clad laminate of a PCB) can be easily prepared and tested. However, this assumption underestimates the practical challenges of sample preparation, especially when the copper pins are sourced from the copper-clad laminate of a PCB.
Challenges in sample preparation
1. Complexity of preparing copper pins from PCB copper clad laminates
PCBs are typically constructed from thin copper foil (typically 17.5–70 µm thick) laminated onto a substrate such as FR-4. Extracting or fabricating copper pins from such copper-clad boards for spark testing presents several practical difficulties:
Material Thickness and Structural Integrity: PCB copper clad laminates are extremely thin, making it difficult to form robust, independent copper pins. Standards require precise electrode dimensions (e.g., 1 mm ± 0.1 mm diameter), but cutting or forming pins from thin copper foil cannot guarantee structural integrity. Copper foil can easily bend, tear, or deform during handling, making it impossible to meet the requirements for consistent spark testing.
Inhomogeneity in material properties: PCB copper-clad laminates undergo processes such as etching, plating, and soldering during manufacturing, resulting in variability in material properties such as thickness, purity, and surface characteristics. These inconsistencies make it difficult to produce standardized copper pins that meet IEC 60601 requirements, impacting test repeatability.
Lack of specialized equipment: Fabricating copper pins from copper-clad PCBs requires precision machining or microfabrication techniques that are generally unavailable in standard testing laboratories. Most labs lack the tools to extract, shape, and polish copper pins from thin copper foil to achieve the required dimensional accuracy and surface finish, further increasing the difficulty of sample preparation.
2. Differences from actual equipment conditions
The oxygen enrichment spark test is designed to simulate the ignition risk of medical devices in real-world environments. However, the use of copper pins from the copper-clad PCB leads to differences between the test setup and actual device conditions:
Non-representative samples: PCB copper clad laminates are part of a composite structure and have different physical and chemical properties than standalone copper pins. Testing with copper pins extracted from the laminate may not accurately reflect the actual behavior of the PCB in the device, such as arcing characteristics or thermal effects in a real-world spark scenario.
Limited applicability of test results: Even if labs can overcome sample preparation challenges, copper probe test results based on copper-clad laminates may not be directly applicable to PCB assemblies in actual devices. This is because the way the copper-clad laminate is fixed to the PCB, its interaction with other materials, and the electrical characteristics of actual use (such as current density or heat dissipation) cannot be fully reproduced in testing.
The infeasibility of laboratory sample preparation
Most market testing labs have equipment and process designs designed for standardized metal electrodes (such as pure copper rods or needles), rather than for materials as thin as copper-clad laminates. The following are specific reasons why labs are unable to complete sample preparation:
Technical limitations: Laboratories often lack the high-precision equipment needed to process thin copper foil into copper pins of standard size and shape. Conventional cutting, grinding, or shaping tools cannot handle copper foil at the micron level, while specialized micromachining equipment (such as laser cutting or electrochemical machining) is expensive and not readily available.
Time and cost efficiency: Even if it were possible to produce copper pins through custom processes, the time and cost required would far exceed the budget and schedule for market testing. Market testing often requires evaluating a large number of devices in a short period of time, and the complexity of the sample preparation process would significantly reduce testing efficiency.
Quality control issues: Due to the material variability and processing difficulties of copper-clad laminates, the prepared copper pins may be inconsistent in size, surface quality, or electrical properties, resulting in unreliable test results. This not only affects test compliance but may also lead to erroneous safety assessments.
Discussion of alternatives
Given the infeasibility of preparing copper pins from PCB copper clad laminates, market testing needs to consider alternative methods to assess the fire risk in oxygen-rich environments. The following are possible alternatives:
Materials analysis alternatives to spark testing:
Composition Analysis: Spectroscopic analysis techniques (such as X-ray fluorescence (XRF) or inductively coupled plasma (ICP)) are used to analyze the composition of the copper-clad PCB in detail, determining the purity of the copper foil, its impurity content, and any oxide or plating components. This information can be used to assess the material's chemical stability and ignition propensity in oxygen-rich environments without the need for actual copper needle spark testing.
Conductivity test:
The conductivity of PCB copper-clad laminates can be measured using a four-probe method or a conductivity meter to assess their electrical behavior in high-oxygen environments. This conductivity data can be compared with the performance of standard copper materials to infer their potential performance in spark testing. These tests can indirectly assess the arc risk of PCB materials in oxygen-rich environments without requiring complex spark testing.
Advantages: The material analysis method does not require the preparation of copper needles, reducing laboratory technical and time constraints. Analytical equipment is more common in most laboratories, and test results are easier to standardize and repeat.
Use standard copper pins: Instead of trying to extract material from the PCB copper clad laminate, use prefabricated copper pins that comply with the IEC 60601 standard. While this may not fully simulate the characteristics of the PCB, it can provide consistent test conditions suitable for preliminary risk assessments.
Simulation testing and modeling: Analyze the arcing and ignition behavior of PCBs in oxygen-rich environments through computer simulation or mathematical modeling. This approach can reduce reliance on physical sample preparation while providing theoretical risk assessment.
Improve test standards: IEC standards bodies may consider revising requirements for oxygen-enriched spark testing.
In conclusion
The IEC 60601 oxygen-enriched spark test is crucial for ensuring the safety of medical devices in high-oxygen environments. However, preparing copper pin samples from copper-clad PCBs presents significant challenges for market testing. The thinness and material variability of the copper-clad laminates, the lack of specialized processing equipment in laboratories, and the discrepancy between test results and actual equipment conditions make this test difficult to implement in practice. Replacing the spark test with material analysis (such as composition analysis and conductivity testing) effectively circumvents sample preparation challenges while providing reliable material performance data for fire risk assessment. These alternatives not only improve testing feasibility and efficiency, but also ensure compliance with the safety requirements of IEC 60601, providing a more practical solution for market testing.
The above is just my personal understanding and thinking, welcome to point out and discuss. Finally, as the manufacturer of this equipment, in actual operation, we found that the above summary.
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Kingpo Technology Launches Latest IEC 60309 Compliance Gauges for Global Markets
2025-07-18
Kingpo Technology Launches Latest IEC 60309 Compliance Gauges for Global Markets
China – July 15, 2025 – Kingpo Technology Development Limited, a leading manufacturer of precision testing instruments, has unveiled its latest range of IEC 60309-2 compliance gauges, designed to meet the most current international standards for electrical connectors and socket-outlets.
Precision Engineered for Global Standards
The newly released gauges (including “Go/No-Go” types for dimensions d1, d2, l1, and compatibility checks) are meticulously crafted to align with the latest IEC 60309 editions, ensuring accuracy for 16/20A to 125/100A connectors across voltage ranges. Key highlights include:
Rigorous Testing: Each gauge is calibrated and certified by CNAS/ilac-MRA accredited laboratories (ISO 17025 compliant).
Comprehensive Range: 12 gauge types covering sockets, plugs, and phase-hole checks (e.g., Fig. 201–215).
Durability: Packed in safety toolboxes with a 1-year warranty under normal use.
Expertise You Can Trust
With decades of experience in metrology, Kingpo Technology combines advanced manufacturing with strict adherence to IEC standards, offering:
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KINGPO Debuts K-SRS System, Achieves Simultaneous ISO 13482 & IEC 60601 Certification
2025-07-12
KINGPO Medical Division today announced that its “K-SRS” full-lifecycle surgical-robot test and validation system has passed its final acceptance and is now commercially operational. Developed by the Medical Division—spun off from KINGPO Instrument in 2018—the platform integrates a sub-micron laser-interferometer spatial-measurement core with a seven-DOF articulated-arm dynamic calibrator and force/position hybrid loading technology. In accordance with the newly published ISO 13482:2025 “Robots for surgery — Safety and performance requirements” and IEC 60601-1-10:2025 “Medical electrical equipment — Particular requirements for surgical robots,” the system completed 28 critical performance and safety validations in real-world surgical scenarios, becoming the world’s first test platform to pass every clause of both standards in a single campaign.
Key Validation Achievements • Spatial Accuracy: ≤15 µm end-effector repeatability and ≤50 µm trajectory-tracking error within a 400 mm × 400 mm × 300 mm workspace (laser-interferometer closed-loop feedback). • Force Control: 0.01 N force resolution on soft tissue, steady-state error ≤0.08 N, overshoot
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