If your digital panel meter suddenly shows zero, your PLC input flatlines, or your transmitter stops responding — you might be experiencing 4-20mA signal loss.
This is one of the most common issues faced in factories, refineries, and automation systems across Malaysia. Let’s break it down in simple terms.
First, What Is a 4-20mA Signal?
The 4-20mA current loop is the standard signal used to transmit readings like pressure, level, temperature, or flow from sensors to controllers, meters, or PLCs.
4mA = minimum value (e.g. 0 bar)
20mA = maximum value (e.g. 10 bar)
It’s immune to voltage drops and signal noise
Commonly used in harsh industrial environments
What Is “Signal Loss”?
Signal loss means the current loop is interrupted, and your device is no longer receiving the 4-20mA signal from the sensor or transmitter.
Symptoms include:
Display shows 0.00 or blank
PLC shows “no signal”, “sensor fail”, or “open loop”
Alarms or interlocks triggered unexpectedly
Top 5 Reasons for 4-20mA Signal Loss (Based on Malaysia Site Cases)
1. Broken or Disconnected Wires
In factories with high vibration or heat, wiring can come loose or get damaged.
Fix: Check for loose terminals or broken cables using a multimeter.
2. Power Supply Failure
Most transmitters require 24VDC. If the power drops, your sensor won’t work—and no current is sent.
Fix: Use a multimeter to confirm 24VDC power is reaching the transmitter.
3. Overloaded Loop (Too Many Devices in Series)
Too many devices sharing the same loop without proper design = insufficient loop power.
Fix: Check total loop resistance. Ensure the power supply can handle all devices connected.
4. Incorrect Wiring or Polarity
Swapping + and – in wiring can cause total signal failure or even damage the transmitter.
Fix: Refer to the sensor manual and recheck terminal connections carefully.
5. Sensor or Transmitter Failure
After years of use (especially in outdoor or high humidity sites), the sensor itself might fail.
Fix: Replace with a new unit (get help from MyCelectric if you need cross-reference).
Tools You Can Use for Troubleshooting
Multimeter (set to mA mode)
Loop calibrator or signal simulator
Spare transmitter (for quick swap testing)
Pro Tip from Our Engineer
When troubleshooting, always check power first, then wiring, before replacing the sensor. In 70% of Malaysian factory cases we’ve handled, the issue is just loose wiring or 24VDC failure—not the sensor.
We Help You Troubleshoot & Replace Sensors Fast
At MyCelectric, we supply and support:
4-20mA pressure, flow, level, and temp transmitters
Panel meters, isolators, and loop-powered devices
On-call support to help you identify signal loss issues fast
Call or WhatsApp us if your Gems, Setra, Finetek, or Contrec sensor is acting up. We can help you diagnose and supply replacements fast.
Related Products We Recommend:
Signal Isolators (prevent interference in long-distance wiring)
Digital Panel Meters (Adtek, Precision Digital)
Loop-powered Transmitters (Gems, Finetek, Anderson-Negele)
Need Help Now?
Email us at sales@mycelectric.com or WhatsApp our engineer. We respond fast – because we know downtime is expensive.
