Multimeter measuring method for detecting fuse resistance
A fuse resistor is a special component that serves as both a resistor and a fuse. It is represented by the letters "RF" or "R" in the circuit.
Selection of Fused Resistors
When selecting, its dual performance should be considered, and parameters such as resistance and power should be selected according to the specific requirements of the circuit. It is necessary to ensure that it can quickly fuse when overloaded, while also ensuring that it can work stably for a long time under normal conditions. Excessive resistance or power cannot provide protection.
Measurement method using a multimeter for detecting fuse resistors
In a circuit, when a fuse is blown open, it can be judged based on experience: if the surface of the fuse resistor is found to be blackened or burnt, it can be concluded that its load is too heavy, and the current passing through it exceeds the rated value by many times; If there are no traces on its surface and it is open, it indicates that the current flowing is exactly equal to or slightly greater than its rated melting value. For the judgment of the quality of a fuse resistor without any trace on the surface, a multimeter with r × 1 gear can be used to measure. To ensure accurate measurement, one end of the fuse resistor should be soldered off from the circuit. If the measured resistance value is infinite, it indicates that the fuse resistor has failed and opened. If the measured resistance value is far from the nominal value, it indicates that the resistance has changed and should not be used again. In maintenance practice, it has been found that there are also a few fuse resistors that are broken down and short circuited in the circuit, and attention should also be paid during testing.
Classification of Fused Resistors
1) Recoverable fuse resistor
A recoverable fuse resistor is a type of resistor that is made by welding a common resistor (or resistance wire) in series with a spring metal ratio (or elastic metal sheet) using low melting point solder, and then sealing it in a cylindrical or square housing. There are several types of shells, including metal and transparent plastic.
Within the rated current, the recoverable fuse resistor acts as a fixed resistor. When an overcurrent occurs in the circuit, the solder joint of the recoverable fuse resistor melts first, causing the spring metal wire (or elastic metal sheet) to disconnect from the resistor. After troubleshooting the circuit, solder the resistor to the metal wire (or metal sheet) as required to restore normal use.
2) Disposable fuse resistor
A disposable fuse resistor, also known as an irreversible fuse resistor, serves as a fixed resistor during normal circuit operation. When its operating current exceeds the rated current, the fuse resistor will melt like a fuse, protecting the circuit. Once a disposable fuse resistor melts, it cannot be repaired immediately and can only be replaced with a new one. Disposable fuse resistors can be divided into wire wound fuse resistors and film fuse resistors according to the material used for the resistor body.
1. Wire wound fuse resistor is a power type glazed resistor with a small resistance value, usually used in circuits with high operating currents.
During the production process, a portion of the power type glazed resistor is wound with thin wires or exposed (without enamel protective layer). In the event of an overcurrent fault in the protected circuit, the thin wire or exposed portion of the resistor (without enamel) will burn out due to overheating, providing protection for the circuit.
2. Film-type fuse resistors Film-type fuse resistors are the most commonly used fuse resistors at present. They are divided into carbon film fuse resistors, metal film fuse resistors and metal oxide film fuse resistors.
