The Classification and Development of the Explosion Proof Temperature Transmitter

Explosion proof temperature transmitter indirectly measures temperature by measuring some parameters of the object with the change of temperature. A good explosion proof temperature transmitter should have many conditions, such as wide temperature range, high precision, fast response, good reliability, low price and so on. The explosion proof temperature transmitter has two types: contact type and non-contact type. The contact explosion-proof temperature transmitter has the characteristics of low price, slow response speed and simple structure. The non-contact explosion-proof temperature transmitter has fast response speed. It can also be used to measure high temperature and corrosive occasions.

Explosion proof temperature transmitters are classified according to the principle

1. Expansion thermometer Expansion thermometer is made on the principle of conducive to thermal expansion and contraction of objects. It can measure objects of about - 200 - 500 degrees Celsius. This is the type of thermometer commonly used.

2. Resistance Explosion Proof Temperature Transmitter The resistive explosion proof temperature transmitter is made by using the principle that the resistance will change with the change of temperature in the temperature field of conductor or semiconductor. As we know, platinum resistance and copper thermal resistance belong to the category of conductors, while thermistors mainly consists semiconductor resistance. Its measuring range can reach 1000 degrees Celsius.

3. Thermocouple Explosion proof Temperature Transmitter The working principle of thermocouple is based on thermoelectric benefit. Two different conductors are composed of closed circuit. Because of the different temperature of two points, thermoelectromotive force will be formed. The thermoelectromotive force is only related to the material and temperature of conductor. Thermocouple explosion proof temperature transmitter can measure a wide range of - 300 - 2800 degrees Celsius.

4. Integrated Explosion Proof Temperature Transmitter The integrated explosion proof temperature transmitter is a kind of explosion proof temperature transmitter which integrates temperature sensor, amplifier circuit and compensation circuit on a very small chip. It is the fastest developing explosion proof temperature transmitter at present. Its advantages are good linearity, fast response and standardized output. Its disadvantages are that the measuring range is narrow, generally in -50-150 degrees Celsius, which is mainly related to the use conditions of components.

Development Stage of Explosion Proof Temperature Transmitter

The development of explosion proof temperature transmitter has roughly gone through three stages:

1. Traditional discrete explosion proof temperature transmitter (including sensitive elements);
2. Analog integrated explosion proof temperature transmitter/controller;
3. Intelligent explosion proof temperature transmitter.

The new explosion proof temperature transmitter is developing from analog to digital, from integration to intelligence and network. The earliest intelligent explosion proof temperature transmitter introduced in the mid-1990s is an 8-bit A/D converter. Its temperature measurement accuracy is low, and its resolution can only reach 1 degree C. A variety of high precision and high resolution intelligent explosion proof temperature transmitter has been developed abroad. They use 9-12 bit A/D converters with resolution of 0.5-0.0625 degrees C. The DS1624 high-resolution intelligent explosion proof temperature transmitter, newly developed by DALLAS Semiconductor Company in the United States, can output 13-bit binary data with a resolution of 0.03125 C and a temperature measurement accuracy of 0.2 C. In order to improve the conversion rate of multi-channel intelligent explosion proof temperature transmitter, some chips adopt high-speed successive approximation A/D converter. After entering the 21st century, intelligent explosion proof temperature transmitter is developing rapidly in the direction of high-tech, such as high precision, multi-function, bus standardization, high reliability and safety, development of virtual sensors and network sensors, and development of single-chip temperature measurement system. At present, explosion proof temperature transmitter as the slave can communicate with the host through special bus interface.