Process instrumentation
Tank level, pressure and flow sensor interfacing.
4-20mA Signal Systems
Industrial 4–20mA signal generator and reader design, sensor interfacing, calibration and monitoring systems.
Overview
What this service covers
Industrial 4–20mA current-loop design — signal generation, loop reading, sensor interfacing and calibration for process instrumentation and plant monitoring.
Client Problems
Problems this service solves
- A legacy 4-20mA sensor needs to interface with a modern microcontroller.
- An existing loop reader drifts or isn't calibrated correctly.
- A signal generator is needed to simulate a sensor for testing a PLC or controller.
- Signal conditioning needs to be isolated and noise-resistant on a noisy plant floor.
Capabilities
What we do
- 4-20mA signal generator and reader circuit design
- Sensor interface and calibration
- Analogue signal conditioning and isolation
- Industrial monitoring integration (RS-485/Modbus, where applicable)
- Review and correction of an existing 4-20mA circuit
Technologies
Tools & platforms
Precision current-loop ICs, isolated signal-conditioning components, and STM32/ESP32-based readout and logging.
Current-loop ICsIsolated signal conditioningSTM32 / ESP32
Development Process
How we approach a 4-20mA project
- 01Loop review
Confirm what's being measured and the existing loop setup.
- 02Circuit design
Design the generator, reader or conditioning circuit.
- 03Calibration
Calibrate the circuit against known reference values.
- 04Integration & handoff
Integrate with the existing controller and hand over documentation.
Deliverables
What you receive
- Schematics and PCB layout
- Calibration notes
- Integration and wiring documentation
Testing & Validation
How 4-20mA circuits get validated
Every circuit is calibrated against known reference values across its full expected range, not just at one point, since a loop that reads correctly at mid-scale can still be off at the extremes. Isolation and noise immunity are checked before the circuit goes anywhere near a live plant floor, and the final calibration is documented so it can be checked again later without starting from scratch.
Applications
Where this is used
PLC/controller testing
Signal generators for simulating sensors during commissioning.
Plant monitoring
Reliable loop reading integrated into a wider automation system.
Related Services
Often paired with
Industrial Automation Systems
The controller this signal feeds into.
PCB Design
The board carrying the signal-conditioning circuit.
Embedded Firmware Development
Firmware reading and logging the loop signal.
Want more background first? Read 4-20mA Signal Generator and Reader Systems.
How We Can Help
How PAK-EL LAB Can Help
If a 4-20mA loop needs to interface with a modern controller, or an existing circuit needs correcting rather than replacing, we can design the circuit, calibrate it and integrate it with your automation system as one project. Scope, deliverables, schedule and quotation are confirmed once we know what's being measured and what's wrong (or missing) in the current setup. We work with clients internationally and collaborate remotely as standard practice.
See also: Portfolio · Industrial Automation Systems · Contact
FAQ
Frequently Asked Questions
Can you fix a 4-20mA loop reader that's drifting out of calibration?
Yes, reviewing and correcting an existing circuit — including recalibrating it against known reference values — is common work, not just new designs.
Can you add RS-485/Modbus output alongside the analogue loop?
Yes, where the plant already uses RS-485/Modbus for monitoring, we can add that digital interface alongside the 4-20mA loop.
Can you build a signal generator to test our PLC or controller?
Yes, a 4-20mA signal generator that simulates a real sensor is a common commissioning and testing tool we build.
Is the signal conditioning isolated for plant-floor noise?
Yes, isolated signal conditioning is the default approach for this work, since unisolated circuits are far more prone to noise-induced reading errors on a plant floor.
Discuss Your 4-20mA Project
Tell us what's being measured and what's wrong with the current setup.