A kind of transducer in fivesegment liquidlevel measurement was designed. Cylindrical fivesegment capacitance was used as level sensor and PCAP01 chip was used to measure capacitance value at each level. With SPI interface technology, microcontroller read the measurement results. Then the data were transmitted to the AD421 chip after they were processed by STM32. Finally, AD421 output 4~20 mA current signal. Experimental results show that the transmitter can reach 05 accuracy class and it can meet requirements of the industrial scene.