proof temperature transmitter
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
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
has fast response speed. It can also be used to
measure high temperature and corrosive occasions.
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
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
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.