In this DIY, we are making a project “4-20mA Current Loop Tester using JRC4558 Op-Amp”. Sensors are an essential aspect of any measurement framework as they help in changing over these real-world boundaries into electronic signals that could be perceived by electronic instruments.
In industry, the normally used sensors are Analog and Digital sensors. Digital sensors communicate with 0’s and 1’s after conventions like USART, I2C, SPI, and so on. What’s more, Analog sensors could convey through variable voltage or current.
A large number of us ought to be comfortable with sensors that yield variable voltage like LDR, MQ gas sensor, Flex sensor, and so on. These analog voltage sensors are combined with “Voltage to current converters” to change over the “analog voltage into the analog current” to turn into a variable current sensor.
Hardware Components
The following components are required to make the Current Loop Tester Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Transistor | BC557 | 1 |
| 2. | Op-Amp | JRC4558 | 1 |
| 3. | Resistor | 300K, 1K, 100R | 1, 1, 2 |
| 4. | Potentiometer | 50K | 1 |
| 5. | Ceramic Capacitor | 100pF 16V, 0.1uF 16V | 1, 2 |
| 6. | LED | – | 1 |
| 7. | Power supply | 5V | 1 |
| 8. | Breadboard | – | 1 |
| 9. | Hookup wire | – | 1 |
| 10. | multimeter | – | 1 |
JRC4558 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of JRC4558
BC557 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of BC557
Current Loop Tester Circuit
Working Explanation
The LED works here as the load and the current loop circuit provide the load with the requisite current. The BC557 which is operated directly by op-amp 4558 provides the load current. A reference voltage of the potentiometer is given with the positive input of the amplifier. The op-amp supplies the bias current to the base of the transistor based on the reference strain. The extra series resistor is supplemented in the potentiometer to restrict both reference voltage and amplifier performance, thereby providing a 0mA to 20mA restriction. Changing the value of the resistor would also change the existing performance cap from minimum to maximum.
Applications and Uses
The important application of a 4-20 mA Current Loop Analyzer is to test, modify and supply information to PLC machines that have a 4-20 mA convention.
