Application of Current Signal in Industrial Field

Abstract: The application information of current signals in industrial sites is provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. The working principle of 4~20ma current loop In the industrial field, using an instrumentation amplifier to complete the signal conditioning and long-term transmission will cause the following problems: *, because the transmitted signal is a voltage signal, the transmission line will be interfered by noise; second, Distributed resistance of a transmission line. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is the details of the application of current signals in industrial sites. The working principle of 4~20ma current loop In the industrial field, using an instrumentation amplifier to complete the signal conditioning and long-term transmission will cause the following problems: *, because the transmitted signal is a voltage signal, the transmission line will be interfered by noise; second, The distributed resistance of the transmission line will create a voltage drop; third, how to provide the operating voltage of the instrumentation amplifier in the field is also a problem. In order to solve the above problems and avoid the influence of related noise, we use current to transmit the signal, because the current is not sensitive to noise. The current loop of 4-20ma uses 4ma to represent the zero signal, and 20ma to represent the full scale of the signal, and the signal lower than 4ma and higher than 20ma is used for various fault alarms. There are two types of 4-20ma current loops: two-wire and three-wire. When the monitoring system needs to drive on-site driving devices such as valves, etc. through a long line, a three-wire transmitter is generally used, where xtr is located at the monitoring system end, and the system directly supplies power to xtr, and the power supply is the third current transmission line. root line. The two-wire system is that the xtr and the sensor are located at the field end. Due to the existence of power supply problems on site, the receiving end generally uses a 4-20ma current loop to supply power to the remote xtr, and 4-20ma is used to reflect the size of the signal. Typical applications for 4 to 20ma products are sensing and measurement applications, see Figure 1. There are many kinds of sensors in the industrial field that can be converted into 4-20ma current signals, ti has some very convenient transmitter chips for rtd and bridge. Because ti's transmitter chip contains general functional circuits such as voltage excitation source, current excitation flow, voltage regulator circuit, instrument amplifier, etc., it can easily convert the signals of many sensors into 4-20ma signals. Most applications of bridge sensors are for measuring pressure. In a practical circuit, if the resistance on each arm of the Wheatstone bridge is 2k, then its equivalent resistance is 2k when viewed from the excitation voltage terminal or the differential output terminal. When there is no stress, its bridge is balanced and the output voltage is 0. When pressure is applied, due to the imbalance of the bridge, a differential voltage will be generated, and the differential voltage will reflect the magnitude of this pressure. Full scale and tone are the two main technical indicators of pressure sensors. The sensors used in the real world all have certain nonlinearity, and their output voltage will change with temperature. The change of output voltage with temperature is not linear, both full scale and tone have this property. 4-20ma sensor signal conditioning solution The 4-20ma current loop is structurally composed of two parts, namely the transmitter and the receiver. The transmitter is generally located at the field end, the sensor end or the module end, while the receiver is generally located at the plc and On the computer side, it is generally in the controller. Two-wire 4-20ma circuit application, the working power and signal share one wire, and the working power is provided by the receiving end. In order to avoid the power frequency interference of 50/60hz, the current is used to transmit the signal. The main issue to consider in a two-wire solution: determine the number of receivers used, when there are multiple receivers, it will require the transmitter to have a lower operating supply voltage. Another consideration is to reduce the voltage drop of the loop current at the receiver. The design of the two-wire scheme needs to consider: (1) the number of receivers in the circuit loop: more receivers will require the transmitter to have a lower working voltage; (2) the necessary working voltage of the transmitter must be certain (3) Determine whether the excitation method of the sensor is voltage or current. Two-wire solution with voltage regulation and reference circuits. The xtr115/116 in the figure is a precise signal converter for 4-20ma signal, it contains a voltage regulator circuit of 5v, which can supply power to the external circuit. A precision on-chip voltage reference can be used for voltage biasing or sensor excitation. The three-wire 4-20ma circuit is designed to provide the working power supply from the transmitter end. In order to avoid the 50/60hz power frequency interference, the current is used to transmit the signal. The xtr regulator and the on-site load share a ground connection. The scheme design needs to consider: (1) the number of receivers in the current loop; (2) more receivers require the transmitter to have a higher working voltage; (3) to ensure the necessary working voltage of the transmitter, And there should be some margin. The three-wire transmitter application scheme provided by ti is shown in Figure 3. In the figure, xtr110 is a precise voltage-current converter for analog signal transmission. It can directly convert the input voltage of 0~5v or 0~10v. Convert to 4～20ma, 0～20ma, 5～25ma output signal.

Beijing Sincerity Automatic Equipment Co., Ltd is always trying to better understand the mass flow meter of innovation, so we can help companies lead the industries.

Beijing Sincerity Automatic Equipment Co., Ltd has had manufacturing experience for over low flow turbine flow meter years. She currently runs a website where they sell . You can visit her site at Sincerity Flow Meter.

We are making mass flow meter available to you at a very low price.

coriolis density meter mass flow meter will help keep your digital fork density meter in a rosemount vortex flow meter state.