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This instrument is based on the latest version of the standard:
ASTM D3874-20 Standard Test Method for Ignition of Materials by Hot Wire Sources and IEC TS 60695-2-20-2021 Glowing/hot wire based test methods–Hot-wire coil test method–Apparatus, verification, test method and guidance.
The new versions of ASTM and IEC standards have undergone significant modifications compared to the previous versions, particularly in terms of sample size range, sample and hot wire treatment, characteristics and accuracy of testing power sources, and testing methods.
Due to the unique nature of testing, many laboratory and factory test results have high dispersion and poor reproducibility, which requires higher requirements for sample processing methods, the structure and accuracy of testing instruments themselves, and the correctness of testing methods.
Although ASTM and IEC standards are relatively similar, there are still significant differences, especially in the characteristics of power sources (one is AC and the other is DC). In theory, these two standard instruments cannot be substituted for each other.
UL laboratory has now started using new standards for sample testing, and testing instruments have also been updated. Compared to ASTM standards, UL laboratories have their own special requirements internally, such as determining the length of hot wire, a more sealed test chamber, and a more stable test current. Its purpose is to ensure the consistency of the testing environment and conditions, in order to obtain consistent and reproducible test results.
The latest IEC standard has completely changed the characteristics of power sources of the old standard, so it can basically be said that the testing instruments have been changed. Compared to ASTM standards, IEC standards provide more detailed and rigorous testing details to avoid differences in test results between different laboratories.
  
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