If you’re working with industrial system modules with 4-20mA interfaces—sensors, PLCs, motor drivers, valves — you know the challenges of debugging, calibration, and adding new features. Understanding fundamentals of 4-20mA loops is essential, and the ProMax CSG01 loop calibrator is a powerful tool to help you work with industrial systems using 4-20mA.
This post will guide you through using the CSG01 Signal Generator, rated specs, pinout and connections, generating simple current signals, advanced features like generating preprogrammed current waveforms, etc. My own experience with the CSG01 has been incredibly positive—it’s saved me significant time and effort, and I’m sure it will do the same for you.
What is a 4 to 20ma Current Loop Signal?
4-20mA Signal is popularly used to transmit process signals(from sensors) to controllers (PLCs) in industry-grade applications. Most sensors, actuators, solenoids, encoders, etc designed for industrial applications have a 4-20mA current interface.
4-20mA Signal is popularly used to transmit process signals(from sensors) to controllers (PLCs) in industry-grade applications. Most sensors, actuators, solenoids, encoders, etc designed for industrial applications have a 4-20mA current interface.
A 4-20mA signal is a common way to transmit sensor data. It uses a current signal that varies between 4 and 20 milliamps (mA) to represent the measured value. For example, consider a 4to20mA temperature sensor with a range of 0°C to 100°C. This sensor will be designed so that 4mA corresponds to 0°C, 20mA corresponds to 100°C, and 12mA corresponds to 50°C. A microcontroller or programmable logic controller (PLC) can then measure this current and convert it back into the corresponding temperature.
Current signals, specifically 4-20mA, are preferred over voltage signals for transmitting sensor data because they are less susceptible to noise, especially over long distances. Additionally, current signals provide a more consistent interface for devices like sensors, motor drivers, microcontrollers, and PLCs, which may operate at different voltage levels (e.g., 5V, 12V, or 24V). Using current simplifies integration and avoids potential voltage compatibility issues.
Why are current signals used over voltage/digital signals?
- Noise Immunity: Industrial environments are electrically noisy. Voltage signals are susceptible to this noise, which can corrupt the data being transmitted. Current loops, however, are far more resistant to electromagnetic interference. Think of it like this: voltage is like pressure in a pipe, easily disturbed by external forces. Current is like the flow rate, much more stable.
- Long Distance Transmission: A key advantage of 4-20mA is its ability to travel long distances without significant signal degradation. The current is maintained consistently throughout the loop, counteracting the effects of wire resistance and voltage drop that plague voltage signals over distance. This is crucial in large industrial facilities where sensors and control rooms can be far apart.
- Simple Implementation and Wiring: 4-20mA systems are relatively simple to design and install. The two-wire system (one for power, one for signal) reduces wiring complexity compared to some other methods. This simplicity translates to lower installation costs and easier maintenance.
- Fault Detection: The “live zero” of 4mA is a brilliant feature for diagnostics. If the current drops to 0mA, it immediately indicates a fault in the loop (e.g., broken wire, power supply issue). This makes troubleshooting much easier compared to voltage systems where a zero reading could be a valid measurement or a fault.
- Signal Scaling and Linearization: The 4-20mA signal makes it easy to represent process variables. The linear relationship between the current and the measured value (e.g., 4mA = 0% of range, 20mA = 100% of range) simplifies scaling and conversion. This makes it straightforward to translate the current signal into meaningful engineering units (like temperature, pressure, or flow rate).
- Intrinsic Safety: In hazardous environments, 4-20mA systems can be designed to be intrinsically safe. This means that the energy levels in the loop are limited to prevent the possibility of igniting flammable materials.
Where is this 4 to 20ma Signal Generator used?
This signal generator can be used to manually generate a 4 to 20mA signal. A knob on the module, lets users simulate a current signal. It is great if you want to do testing/calibration/etc without having to connect a live sensor.
Beyond basic manual operation, the CSG01 offers advanced programmable waveform generation. This feature allows for automated ramping of the 4-20mA output current over a user-defined time period. This capability makes the device a true signal generator, capable of producing dynamic output profiles. Automated ramping is valuable for tasks such as automated testing or simulating the changing output of a sensor (e.g., a temperature sensor) or controlling an actuator’s position.This is the reason we call it a signal generator – because it can generate a preprogrammer output loop current curve automatically
- Receiver Calibration: It is used calibrate receivers (like PLCs / motor drivers / displays / values) that interpret a 4-20mA signal. By injecting a known current, technicians can verify that the receiver correctly converts it back into the corresponding measurement value. This will be difficult (practically infeasible) with a live temperature sensor, where the sensor will have to be exposed to full scale ambient temperatures to simulate the entire 4 to 20mA signal
- Useful for testing/calibrating the controller. Once the controller is working with the generator, we can then connect a live sensor and start working.
- Bypass defective sensors during testing: The current calibrator is connected in place of the sensor. The technician then uses the calibrator to generate a 4-20mA signal that represents the expected output of the sensor as if it were working correctly. The technician can then take a informed decision on replacing the right sensor in a system.
Bottom Right: Signal Generator is outputting a current signal.
Left: Multimeter reading the output signal.
Technical Specifications of the ProMax CSG01
The ProMax CSS01 is the original high quality version of the low cost 420LGPM Current Signal Generator. We have carefully ensured high quality design focussed on performance and reliability, components are sourced from reliable manufacturers and the output accuracy is as per the rated specs. Avoid buying cheap clones / low cost alternatives else you will surely see a degradation in performance and frequent failures.
- Input Voltage : 15V-30V (wide operating range suitable for all common industrial operating voltages – 5V, 12V & 24V)
- Output Range: 4-20mA (can be tuned to 0 to 24mA)
- Display mode: Real current value in mA / as percentage 0-100% / 0-50Hz
- Sampling Resistance: Less than 500Ω
- Output accuracy: ±0.5%
- Display accuracy: 0.01
- Mounting Style: Panel Mount, Press Fit (great for cabinet enclosures, manageable for handled operation!)
Check out our online store – www.probots.co.in to find all the parts for your projects! We have 2000+ Electronic Modules, Sensors, and Components for all your electronics projects.
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How to use the ProMax CSG01 Current Signal Generator?
While this two-terminal signal generator or loop calibrator is incredibly user-friendly, foregoing complex menus and software, it’s important to remember the fundamentals of 4-20mA current loops. Once you grasp the basics, connecting this device is straightforward: simply insert it in series with your signal, and you can begin outputting a 4-20mA signal.
You can purchase this 4-20mA signal generator here – Buy Now
Connections: How to integrate the CSG01 with your system?
This signal generator features a simplified, two-terminal design. It must be connected in series with a DC power supply ranging from 15 to 30V. The non-polarized connectors offer protection against accidental reverse polarity connections, eliminating the risk of damage from incorrect wiring. However, the supply voltage should never exceed 30V; for safe operation, it’s best to keep the voltage at or below 24V.
On powering, the signal generator starts outputting a 4-20ma Signal, and the current value is shown on the display.
CSG01: How to use Menu (Basics)
- Adjusting the output current: The generator has a knob which can be rotated to adjust the output current. Use the knob to set the desired output current. Turn Clockwise to increase current and anticlockwise to decrease the current.
- Accessing the Settings Menu: The knob can also be pressed to access the onboard settings menu. The module has several advanced features that can be accessed from the settings menu –
- Change the Knob Adjustment Sensitivity – Coarse and Fine Adjustments Settings are available
- Generate automatic time varying current signals
- Generate 1Point or multipoint current signals
- Adjust 4to20mA endpoints – great for calibration, adjusting output between 0 to 24mA for to simulate some odd sensor!!!
- To access settings, press and hold the knob for a few seconds and enter the password. Rotate clockwise for “+”, Rotate anticlockwise for “-”, Press the Knob to “confirm”
Read Part 2 of this article which explains more features of this module, click here.
Check out our online store – www.probots.co.in to find all the parts for your projects! We have 2000+ Electronic Modules, Sensors, and Components for all your electronics projects.
You can purchase this AJ SR04M Waterproof Ultrasonic Sensor here – Buy Now
4 TO 20 MA OUTPUT MODULE 4 TO 20 MA SIGNAL GENERATOR