Three-wire and four-wire transmitter with the above advantages are not about to be replaced by two-wire transmitter STG74L, from the transmitter chip supply and demand dynamics and the amount of foreign trade to a smattering evident STG74L Honeywell, ER When you use the transmitter to be installed in the power line field devices and a microcontroller as the core of the monitoring system are located further away from the scene monitoring equipment room STG74L transmitter, both generally tens to hundreds of meters apart, even more away. Device-site environment is more severe, strong signal will produce a variety of electromagnetic interference, lightning sensor will produce a strong surge pulse line STG74L, in this case, a thorny issue microcomputer application system encountered is how harsh environments Under long-distance transmission of small signals reliably. Two-wire transmitter output current is 4 ~ 20mA, through precision resistor 250Ω into an analog voltage signal 1 ~ 5V or 2-10V The conversion to a digital signal has a variety of methods, if the system is in the environment is more severe Long-term use of the industrial site, and therefore need to consider the safety and reliability of the hardware system works. Input Module system adopts LM231 voltage to frequency conversion device converts the analog voltage signal into a frequency signal photoelectric coupled device TL117 perform analog and digital isolation. While the analog signal processing circuits and digital signal processing circuits using two independent power, analog and digital grounds separated from each other, which can improve the security of the system work. Use VFC LM231 device also has some anti-high-frequency interference. In many applications, microprocessor controlled, have to use the transmitter to the microcontroller can not directly measure the signal into a single chip can handle the electrical analog signals, such as current transmitter, pressure transmitter, temperature transmitters, flow rate change delivery and so on. "Automatic Control Theory", the transmitter is converted to an output signal of the sensor can be identified as controller signal converter. As it is common because sometimes the sensor output signal of the sensor has been most modern general-purpose controller may receive a signal which the transmitter may not be converted directly identified as the controller. Therefore, the "transmitter" meaning in the traditional sense should be: "the sensor output signal is converted to a controller or measuring instruments can be the instrument of acceptance of the standard signal." In the automatic control: Source -> Sensors -> Transmitter -> operator controller -> Actuator -> control output. STG74L pressure transmitter, STG74L, China-Technology provided by the Jinan-Technology Co., Ltd. Jinan Huahui Technology Co., Ltd. (www.cnhuahui.com/) strong, credible, in Jinan, Shandong pressure instrumentation industry has accumulated a large number of loyal customers. The company better work attitude and constantly improving innovative ideas will lead China-Technology into the brilliant and you work for a better future!