In industrial production, in order to increase the loading capacity of the equipment and ensure that the equipment connected to the same signal does not interfere with each other, and to improve the safety performance of electric control, it is necessary to collect, calculate, isolate and amplify the voltage, current, frequency, resistance and other signals output by instruments or sensors , After conversion, transmission and interference removal processing, the industry-wide standard analog current or voltage signal is obtained, and it is safely sent to the secondary instrument or PLC/DCS/PC for use. Users who use analog signal isolators/isolation amplifiers/isolation transmitters/data collectors and other products sometimes encounter technical problems such as field signal matching, load matching, high-frequency interference, multi-channel signal interference, or active and passive, 2/3/4 wire system, loop feeding, etc. selection and application method issues.
As a domestic senior analog signal technology application research and development manufacturer, Sunyuan Technology, based on years of R&D and production experience and extensively collected by technical service engineers, provides valuable feedback from users in various environments on the industrial site. While improving the various technical indicators, we will record and collect some technical problems encountered by engineers on site, hoping to provide users with some technical references and on-site application solutions support. In the future, if we collect more solutions to technical problems, we will update the information in time. Users are welcome to send any problems or complaints and suggestions encountered in the field application to our company's technical support mailbox: szsy@sun-yuan.com; sy8@sun-yuan.com
common problem:
1. How to distinguish and select the signal isolator|isolation amplifier|isolation transmitter|distributor|conditioner|safety barrier?
Signal isolator: Directly isolate and transmit analog 4-20mA current signal or 0-5V voltage signal, which is divided into active type and passive type.
Active signal isolators need an external auxiliary power supply. Because of the external electrical energy support, the signal will not be lost during the isolation transmission process, and the load capacity is strong.
0-±10V signal isolator: ISO EM U6-P1-O10
Passive signal isolators do not require external auxiliary power supply, and generally adopt loop power stealing technology, which has some loss in signal transmission and weak load (≤350Ω).
4-20mA passive signal isolator: ISOS 4-20mA
Isolation amplifier: generally active type, can isolate, amplify and convert analog 4-20mA current signal or 0-10V voltage signal. The isolation amplifier needs an external auxiliary power supply. Due to the external electrical energy support, the signal can be isolated, amplified, and converted without loss during the isolation transmission process. After the step-by-step amplification of the active amplifier, it can drive some electric valves, micro motors, etc. Devices with heavier loads.
4-20mA to 0-10V isolation amplifier: ISO EM A4-P1-O5
Isolation transmitter: In addition to the general functions of signal isolator and isolation amplifier, it can also isolate and convert Pt100/Cu50 temperature, frequency, displacement resistance, PWM, true effective value, speed, differential signal, and AC signal into Standard 4-20mA/0-10V analog signal or pulse square wave signal. The active isolation transmitter needs an external auxiliary power supply. Because of the external electrical energy support, the signal will not be lost in the isolation transmission, and the load capacity is strong.
Pt100 to 4-20mA isolation transmitter: ISO Z-W-P-O
Passive isolation transmitter does not require external auxiliary power supply, and generally adopts loop power stealing technology, with some loss in signal transmission and weak load (≤250Ω). 0-75mV to 4-20mA isolation transmitter: ISOS V-4-20mA
Isolation distributor: In some occasions of industrial control system, a two-wire 4-20mA loop feed transmission method is adopted. While distributing 24V working power to primary instruments such as sensors and transmitters, the variable signal of the instrument must be collected and passed The loop is transmitted to the secondary instrument or other equipment for use.
4-20mA loop feed isolation distributor: ISOS 4-20mA-F
Isolation conditioner: It is a special device for conditioning the active signal of the primary instrument and the live signal of the current loop interface. It is used to match the sensor signal with the analog input interface after the sensor signal is collected. It can solve the conflict between the 4-20mA active signal collected by the sensor and the live signal at the receiving port of the two-wire current loop power supply loop.
4-20mA current loop isolation conditioner: ISOS 4-20mA-E
Isolation safety barrier: It is often used in some occasions where high voltage endangers the safety of people and equipment, such as power equipment, medical equipment, and rail transit facilities. The internal design of the product adopts high isolation measures, so that the analog signal can reach 6000VDC insulation voltage transmission without distortion between the primary instrument and the secondary instrument.
6000VDC analog signal transmission high isolation safety barrier: ISO EMH series
2. What is the load capacity of the passive signal isolator, active signal isolating amplifier, and isolating transmitter?
Passive signal isolator/signal transmitter produced by Shunyuan Technology: (0-20mA/4-20mA) current output type conventional product load capacity conventional value is 250Ω, the maximum load value is 700Ω/24VDC, please refer to each Detailed technical information of the type of product. (0-2.5V/0-5VDC) The carrying capacity of voltage output conventional products must be ≥5KΩ.
Active signal isolation amplifier/isolation transmitter: (0-20mA/4-20mA) current output type products with a normal load capacity of 350Ω, of which the maximum load value of magnetic isolation type products is 20mA output/750Ω, photoelectric isolation type products The maximum load value is 20mA output/600Ω. (0-5V/0-10VDC) Voltage output type conventional products with load capacity≥2KΩ. (Note: The user can customize the output load capacity beyond the conventional value, or 0-500mA/0-1A high current special products).
3. What is the working principle and function of analog signal isolator/isolation amplifier/isolation transmitter?
Working principle: The analog signal output by the sensor, transmitter, PLC or instrument is modulated and transformed into a high-frequency carrier signal by the electronic circuit, which is carried out through the photoelectric coupling circuit or the magnetoelectric coupling circuit (I/I, V/V) Isolated transmission, and then through the demodulation circuit to restore the analog signal or one-to-one correspondence with the original signal and converted (V/I, I/V, V/F, F/V, Pt100/V, PWM/I, RMS/V , R/I, S/I, etc.), while isolating the power supply, signal input and output power supply. Therefore, these devices can meet the anti-interference requirements of 3000VDC isolation between signal input, signal output, and power supply ground in the industrial field.
Device function:
1. Protect the control loop of the upper computer.
2. Reduce the influence of environmental noise on the test circuit, and can overcome the frequency converter noise and various high and low frequency pulsation interference.
3. Suppress the interference of the circulating current of the common ground wire and the pulses of the frequency converter, solenoid valve, thyristor, etc. to the equipment, and at the same time have the function of limiting the pressure and the current for the lower-level equipment. It is a transmitter, instrument, frequency converter, solenoid valve PLC/DCS Faithful protection of input, output and communication interface.
The DIN35 series standard 35mm guide rail deck structure is easy to install and can effectively isolate: signal input, signal output, and the potential difference between the power supply and the ground.
