CONTACT RESISTANCE MEASURING DEVICE AND MEASURING NEEDLE THEREFOR

摘要

A contact resistance measuring device has two current probes connected to the terminals of the section to be checked and two voltage probes. The current probes are connected to an A.C. circuit powered by a current generator and the voltage probes are connected to a voltage measuring circuit selectively set to the frequency of the feeding current. The voltage probes (8) and current probes (7) are connected separately in pairs and the conductors (20, 21) of the voltage probes (8) are connected to an area (A) that forms only a fraction of the area (A+B) enclosed by the cables of the current probe (7). A measuring needle for contact resistance measuring devices based on the four-point contact principle has a hollow current electrode (7) fixed in an insulated envelope (6), containing an insulating socket (9) in which the voltage probe can move axially. The voltage probe (8) is insulated from the current electrode (7) and ends with a tip (13), whereas the end of the current electrode (7) is located at a predetermined distance behind the tip (13) and the resilient path of the voltage probe (8) is longer than the said distance. The measuring needles are arranged in pairs in the resistance measuring device. Within each pair, the voltage probe (8) of one measuring needle is connected to the other measuring needle by a cable (18) that passes radially through the insulating screen (19) of the insulated envelope (6), penetrates into the other needle through its insulating screen (19) and extends, together with the conductor (21) connected to its voltage probe (8), up to the sheath of the cable of the current electrode (7).