Introduction: Passive, in electronics, refers to devices that can operate without a power supply in a circuit when there is a signal. Devices that can operate without a power supply are usually referred to as passive devices. The commonly used passive components in circuits are diodes, resistors, inductors, capacitors, and other components. Devices in circuits that require an external auxiliary power supply to function properly are called active devices. Active devices are generally used to isolate, amplify, convert, and transmit signals. Commonly used active devices include transistors, power amplifiers, signal isolators, isolation amplifiers, field-effect transistors, thyristors, and other devices. Shunyuan Technology has launched a series of new low-cost, small volume passive (without external auxiliary power supply) analog signal isolators based on the current industrial Internet's needs for matching various sensors, transmitters, PLC and DCS systems on the industrial site, which are available to sensor and instrument manufacturers and industrial Internet system integration design engineers for selection. The following recommendations are for several new two-wire 4-20mA output systemsPassive analog signal isolatorThe optional technical scheme is for reference when manufacturers and industrial Internet system integration engineers select signal isolator applications on site.

Passive signal isolator application 1: Passive DC unidirectional and bidirectional voltage and current, electronic ruler displacement resistance signal to two-wire current signal isolator

The passive displacement resistance signal (ISO R-O), analog voltage signal (ISO U-O), and analog current signal isolator (ISO A-O) transmitter is the industry's smallest and low-cost passive loop fed analog signal isolation transmitter IC. This IC has efficient signal coupling transformer loop feeding technology and provides power operation through the post stage current output loop feeding method, without the need for an external working power supply. The IC is matched with sensors, instruments, PLC/DCS in the design scheme, and can adapt to analog voltage, current or displacement resistance signal input of various specifications. After amplifying, conditioning, isolating and transmitting the active signal of the two-wire/three wire/four wire universal sensor in the industrial field, the IC outputs the two-wire analog current signal of 4~20mA/2-10mA/4-12mA/4-8mA/12-20mA and other parameters. The core components in the technical solution include passive displacement resistance signals (ISO R-O), analog voltage signals (ISO U-O), and current signals (ISO A-O). The transmitter is designed as a high-precision, small-sized standard SIP12 Pin flame-retardant IC package, which adopts magneto electric isolation coupling method and high-performance post feeding technology. It can achieve precise isolation and conversion of DC voltage, current, single and bidirectional signals, angular displacement, electronic ruler, potentiometer and other analog signals to two-wire loop feeding current loop signals, and is matched with various types of instrument standard analog input ports (such as PLC, DCS, FCS). The core products of the solution include PCB board installation with small volume IC packaging and DIN35 standard rail installation. The DIN rail installation can achieve signal isolation and conversion functions for industrial sites, including one in one out, one in two out, one in three out, two in two out, four in eight, and sixteen signals. Users can choose the technical solution according to their on-site needs.

Passive signal isolator application 2: Passive low-cost, small volume two-wire 4-20mA (0-20mA) current loop analog signal isolator

A two-wire passive ISO 4-20mA (SIP12 Pin package) and ISOS 4-20mA (SIP7 Pin package) 4-20mA current loop signal isolator is a passive signal isolation module that uses a front-end 4-20mA (0-20mA) current signal input and a back-end 4-20mA (0-20mA) current signal output. The solution adopts electromagnetic isolation mode and high-efficiency input loop electricity theft technology, effectively solving the problem of dependence on power supply for current signal isolation between instruments and sensors, and achieving high-precision and high linearity isolation of 4-20mA (0-20mA) standard signals. In the scheme design, passive signal isolators obtain energy from the current circuit of the sensor, and after isolation, output active 4-20mA analog signals to drive or control instruments, PLCs, and DCS devices. The core products of the solution include PCB board installation with small volume IC packaging and DIN35 standard rail installation. The DIN rail installation can achieve isolation and conversion functions for multiple signals such as one in one out, two in two out, and three in three out for industrial sites. Users can choose the solution according to their on-site needs.

Passive signal isolator application 3: Passive low-cost, small volume two-wire 4-20mA loop fed analog signal isolator

The ISO 4-20mA-F (SIP12 Pin) and ISOS 4-20mA-F (SIP7 Pin package) 4-20mA current loop signal isolation distributor is a two-wire circuit powered isolation module. By using the back-end power supply method, the front-end two-wire equipment is powered and receives a 4-20mA current signal output from the two-wire equipment. After module isolation, the 4-20mA current signal is output to the sensor for operation. This scheme adopts electromagnetic isolation mode and high-efficiency post stage feeding technology, effectively solving the problem of dependence on power supply for current signal isolation, achieving precise isolation and transmission of standard signal 4-20mA, and can be matched with various instrument two-wire circuit power supply analog input ports (such as PLC, DCS system, etc.).

Passive signal isolator application 4: Passive low-cost, small volume analog voltage to two-wire system 4-20mA current signal V/I conversion signal isolator

ISO V-4-20mA (SIP12 Pin) and ISOS V-4-20mA (SIP 7Pin) passive V/I conversion analog signal isolation transmitters are signal isolation transmission modules powered by voltage input and two-wire current output circuits. By feeding through the downstream current loop, a set of 5V (3mA) functional extension power supply is provided to the input terminal to power the front-end equipment, and the voltage signal output from the front-end equipment is received. After module isolation, a standard two-wire current signal of 4-20mA is output. This scheme adopts electromagnetic isolation mode and high-efficiency post feeding technology to achieve precise isolation and conversion of voltage signals to 4-20mA standard signals, which can be matched with analog input ports of various instruments (such as PLC, DCS systems, etc.). This technical solution is very convenient to use, without the need for any additional components, and can achieve voltage signal isolation and transmission for voltage signal input, displacement potentiometers, and other power distribution sensors or bridge (weighing) detection circuits.

Passive signal isolator application 5: Passive low-cost two-wire 4-20mA current to analog voltage signal I/V conversion signal isolator

The ISO 4-20mA-O series (SIP12 Pin package) two-wire passive 4-20mA to voltage signal isolation converter can isolate and convert the input active 4-20mA current signal into a voltage signal I/V conversion output. This scheme adopts a two-wire input circuit power supply method, efficient signal circuit electricity theft technology, and does not require an external working power supply, greatly simplifying the user's design and reducing the user's wiring cost. The module contains current signal modulation and demodulation circuit, signal coupling isolation and transformation circuit, power inverter circuit, subtraction circuit, buffer processing output circuit, etc. The small input equivalent resistance enables the product to collect current signals from the sensor signal output circuit and achieve a voltage drop of ≤ 10V when inputting a 20mA signal. This meets the needs of users to achieve long-distance and distortion free signal transmission and transformation without the need for external auxiliary power supply.

Application of two-wire signal isolator 6: Passive low-cost, small volume two-wire 4-20mA current loop signal isolator

The ISO 4-20mA-E (SIP12 Pin package) and ISOS 4-20mA-E (SIP7 Pin) two-wire passive 4-20mA analog isolation conditioning controllers can convert input active 4-20mA current signals into isolated passive control signal outputs, which are used to control the power supply of the two-wire circuit (explosion-proof mode) 4-20mA current loop, achieving on-site matching of sensor signal acquisition and analog input interface active loads, effectively solving the problem of power conflict between the active 4-20mA current signal acquisition and the receiving port of the two-wire current loop power supply circuit. This scheme adopts high-efficiency loop electricity theft technology, which does not require independent power supply and is very convenient to use. Users can adjust the potentiometer for ADJ calibration.

Application of 2-wire Signal Isolator 7: Passive Low cost, Small Volume 2-wire PWM Signal to Analog Signal Isolator

The ISO D-O1 series (SIP8 Pin package) is a passive PWM pulse width modulation signal isolated conversion to a two-wire 4-20mA transmitter IC. The IC works by feeding the PWM signal output from the front-end device through the back-end (output terminal) current loop, and outputs the corresponding 4-20mA standard two-wire current signal after isolation conversion. The PWM pulse width transmitter scheme is designed as a SIP8 Pin (single row 8-pin direct insertion package) small-sized PCB board soldering installation method. The IC contains signal coupling high-speed isolation conversion circuit, precision reference voltage source switch control circuit, low-pass filtering circuit, drive amplification circuit, VI conversion circuit, etc. It has the characteristics of high PWM signal conversion accuracy, good linearity, and wide output circuit power supply voltage range (12-36VDC). The highly integrated process structure and new technology isolation measures enable the core components in this solution to achieve 3000VDC isolation between signal input and output, and meet the requirements of industrial grade harsh working environments with wide temperature, humidity, and vibration.

Application of 2-wire Signal Isolator 8: Passive 2-wire Pt100/Cu50 Thermal Resistance Temperature Measurement Signal Circuit Feed Signal Isolator

ISO Z-W-O1 small volume (12 pin single in line IC package SIP12 pin) low-cost passive two-wire 4-20mA loop fed thermistor signal isolation transmitter, mainly used for the acquisition, isolation and transmission of three wire, four wire or two-wire Pt10/Pt100/Pt1000 or Cu50/Cu100 temperature sensor signals. The solution is used for temperature detection in industrial sites, which can convert the temperature signal collected by the thermistor sensor into a linear proportional standard 4-20mA current signal output according to the change amount.

ISO Z-W-O1 adopts electromagnetic isolation mode and high-efficiency post feeding invention technology, which can achieve precise isolation and conversion of temperature signals output by thermal resistance sensors to 4-20mA standard signals without the need for independent power supply. It can be directly matched with analog input ports of various commonly used instruments and meters (such as PLC, DCS systems, etc.). The IC contains signal modulation and demodulation circuits, signal coupling isolation conversion circuits, high-performance DC-DC boost circuits, signal zero points, full-scale calibration circuits, Pt100 thermal resistance linearization, long line compensation, interference suppression circuits, etc. The output circuit has a wide voltage range (12-36VDC), high conversion accuracy, and good linearity. The full and zero points are adjusted and calibrated on-site by the user through an external potentiometer.

Application 9 of Two Wire Signal Isolator: Passive Two Wire AC Current and Voltage Signal to 4-20mA Analog Signal Isolator

The DIN ISO AC-O1 series AC/DC passive two-wire signal isolation transmitter is an isolation transmitter that can output a DC standard 4-20mA current signal in a linear proportion of the measured AC current and voltage. Equipped with corresponding indicator instruments or directly transmitted to the DCS/FCS system, to achieve measurement and control of AC voltage or current in the system.

The output of this module is designed for a two-wire power supply circuit with 24VDC and sampling resistors (two-wire instruments) connected in series, matching the analog input ports of commonly used analog input interface boards (upper computers), PLCs, DCS, or other instruments in the current industrial field. In the scheme design, high-efficiency loop electricity theft technology was selected without the need for independent power supply. The two-wire loop power output method used can save two power lines, greatly simplifying the user's system scheme design and reducing the user's wiring cost.

In the scheme design, the working power supply circuit of the indicator instruments, PLC or DCS devices in the system is fully utilized to isolate the input circuit device of the signal from the output detection and control circuit, which improves the reliability and stability of the system operation, fully guarantees and improves the safety factor of equipment and personnel. Therefore, this scheme is widely used in the fields of power remote monitoring, power instruments and meters, medical equipment, industrial automation, etc.