These days, the development of intrinsically safe type level and temperature transmitters for ship's cargo tanks are very important because these transmitters are installed in hazardous area which has an explosive possibility. In the hazardous area, the design, installation and operation of the transmitters must be accomplished with the concept of explosion proof.
In this paper, we have redesigned a level and temperature transmitter being generally used in safety area, in order to use in hazardous area. We have discussed the concept of explosion proof and have selected the barrier considering the fault voltage and fault current of transmitter. By criteria of IEC 60079-11, the method reducing internal unprotection capacitance of transmitter is presented and we have designed the circuit pattern of the board and molded the electronic circuit board which is exposed to sea water.
We have measured the error, accuracy and safety parameter of the transmitter. The parameter of transmitter was matched to Z779 zener barrier each other and the error of level was less than 0.1% and the accuracy of temperature was less than 1℃. Therefore the transmitter was proved for the intrinsically safe type and it will be contribute to the development of signal analysis, system control of the hazardous area.