Changzhou Hengto Electronic Weighing Apparatus Co., Ltd. specializes in the production and operation of various types of transmitters. Mainly; KMO1, KM06 and other types of sensors. With output voltage and current, two-stage amplification and ASIC, it is widely used in batching control systems in cement, metallurgy, chemical and other industries.

It is generally required in the industry to measure various types of electrical and non-electrical physical quantities, such as current, voltage, power, angle, etc., which need to be converted into a receivable DC analog electrical signal to be transmitted to a control room or display device hundreds of meters away. This device that converts the measured physical quantity into a transmittable DC signal is called a transmitter. The industry is usually divided into power transmitters and non-electricity transmitters.

The traditional output DC signal of the transmitter has 0-5V, 0-10V, 1-5V, 0-20mA, 4-20mA, etc. The most widely used current is to transmit analog quantity with 4~20mA current. The most widely used in the industry is to use 4 to 20 mA current to transmit analog quantities.

The reason for using the current signal is that it is not susceptible to interference. And the internal resistance of the current source is infinite, the wire resistance is connected in series in the loop without affecting the precision, and can be transmitted hundreds of meters on the ordinary twisted pair. The upper limit is 20 mA because of the requirements of explosion protection: the spark energy caused by the current interruption of 20 mA is not enough to ignite the gas. The reason why the lower limit does not take 0mA is to detect the disconnection: it will not be lower than 4mA during normal operation, and the loop current will drop to 0 when the transmission line is disconnected due to a fault. Usually take 2mA as the disconnection alarm value.

The current-type transmitter converts the physical quantity into a 4~20mA current output, which must be supplied by an external power supply. The most typical is that the transmitter needs two power lines, plus two current output lines, a total of four lines, called a four-wire transmitter. Of course, the current output can be shared with the power supply, which saves one line and is called a three-wire transmitter.