Four-wire system resistance measuring line on-off detection device and judgment method

The invention aims to provide the four-wire system resistance measuring circuit on-off detection device and the judgment method, which are low in cost, convenient to transplant, suitable for a small-spacing test environment, and capable of improving the small resistance measurement precision and the data reliability and automatically judging whether an open circuit exists in a test loop path or not. The circuit comprises a desk type universal meter, a resistor to be measured, a constant current source, an operational amplifier, an analog-to-digital converter, a first resistor, a second resistor, a third resistor, a first relay and a second relay, an OUT pin and an SET pin of the constant current source are connected with one end of the resistor to be measured, and the other end of the resistor to be measured is grounded through the first resistor. An OUT pin of the operational amplifier is divided into two paths, one path is connected to an IN + pin of the analog-to-digital converter through the second resist