The invention relates to a precise resistance measuring device. One end of a
resistor to be measured is connected to the
anode of a power supply through a reference
resistor and a current-limiting
resistor, and the other end is grounded through a bias resistor; four input ends of a
cross bar switch are respectively connected to two ends of the reference resistor and the resistor to be measured, and two output ends of the
cross bar switch are respectively connected to the same-phase input end and the reverse-phase input end of a
signal amplification circuit; the
signal amplification circuit is connected to the
data signal input end of a central processor through an A / D converter; the
data signal output end of the central processor is connected with a memory; the
control signal output end of the central processor is connected with the
control signal input end of the
cross bar switch to control the two output ends of the cross bar switch to sequentially output positive and
negative voltage of two ends of the reference resistor and positive and
negative voltage of two ends of the resistor to be measured; the positive and
negative voltage of two ends of the reference resistor and the resistor to be measured is stored in the memory by the central processor through the
processing by the
signal amplification circuit and the A / D conversion by the A / D converter; and the central processor transfers the positive and negative
voltage difference of the reference resistor and the positive and negative
voltage difference of the resistor to be measured and carries out calculation to obtain the resistance value of the resistor to be measured.