As the national implementation of ccc compulsory produc […]
As the national implementation of ccc compulsory product certification of products, wire and Electric Cable testing items in the national standards are described in detail, including electrical properties, mechanical properties and fire-retardant properties and other aspects. Among them, the electrical properties of the quality inspection agencies in the wire and cable testing is an important project, the main test content DC resistance test, insulation resistance test, frequency withstand voltage test and impact voltage test. In addition to electrical properties, electric wire and cable testing items also include structural dimensions and signs. For fire-resistant cables and fire-resistant cables, in addition to the above items also include flame retardancy, low smoke and halogen requirements and fire-resistant properties.
The detection of DC resistance, mainly for electric wire and cable conductivity. Therefore, the value of DC resistance, electric wire and cable can reflect the quality of electric wire material and the thickness of the diameter of the degree. Wire and cable diameter in the cross-sectional area of the case, the conductor material will determine the quality of its DC resistance. The standard specifies the maximum resistance of the conductor at 20 ℃, the unit is ω/km, that is to say the standard is based on the conductor resistance per kilometer for comparison, the measured resistance value of the wire and cable first Converted to DC resistance at 20 ℃ per kilometer, if the measured value is less than the required standard value, then the sample is qualified, otherwise they are substandard products.
Wire and cable DC resistance detection methods are mainly bridge method and current method two. Among them, the bridge method of single-arm bridge method and double-arm bridge method. Single-arm bridge method is mainly used in wire and cable resistance is 1ω above, the double-arm bridge law for resistance of 1ω below. Current method, also known as micro-Europe meter method, can be based on different predictors and take different currents, measuring a wide range. When using dual-arm bridge and current sensing to detect resistance, a four-terminal measurement fixture can be used to eliminate the negative effects of test wire resistance and contact resistance at the time of measurement.
In the purchase and use of wire and cable, we must adopt those who pass the national ccc mandatory product certification and quality supervision departments of the regular inspection of qualified products manufacturers.