Sensor stopped transmitting – LED OK after battery replacement but no packets in Node-RED

Hardware
1

Hi everyone,

I need some help troubleshooting an NCD Wireless 2 Channel 4-20mA Receiver that stopped transmitting.

Here is the situation:

  • The sensor stopped sending data on January 11th.
    I found that the lithium batteries were dead, so I removed the receiver from the machine, disconnected CH1 and CH2, and brought the device to my desk.
  • I inserted new batteries and now the LED is blinking normally again, so the receiver seems powered and alive.

Before reinstalling it back in the production area, I wanted to perform a bench test to confirm that it can communicate with the NCD EG5120 gateway

My test setup:

  • Sensor with new batteries, on my desk
  • Gateway online
  • Node-RED open
  • I am monitoring the debug node associated with this sensor (debug 26)

Problem:
The sensor is NOT sending any packets to the gateway — nothing appears in Node‑RED debug for this device. Even after factory reset.

So now I’m unsure what the correct behavior should be:

  1. Is a desk test valid?
    Does the sensor transmit even if CH1/CH2 probes are disconnected, or does it only send packets when installed on the machine?

  2. Could I be missing a step to make it communicate again with the EG5120 gateway?
    (Pairing, network ID, etc.)

  3. Is it normal that the LED blinks but the gateway receives no packets?
    Could the sensor have lost its pairing or configuration when the batteries died? As i said i already performed several hard reset of the receiver and also restarted the gateway from its dashboard.

At this point I’m not sure if:

  • The bench test is not valid,
  • The sensor needs to be re-paired with the gateway,
  • Or if I’m simply not triggering the correct transmission test.

Any guidance on how to properly test the sensor on the bench — or how to ensure it talks to the gateway again — would be greatly appreciated. Thanks!!

2

Hi @davidemagno First, I recommend monitoring the battery levels on your sensors. A good rule of thumb is to schedule a battery replacement once the voltage drops below ~2.9V.

Regarding your bench test, the setup appears correct, and the sensor should be communicating with your gateway. To help us narrow down the cause of the connection issue, could you please confirm the following:

  1. Antennas: Are the antennas securely connected to both the gateway and the sensor?
  2. LED Diagnostics: Could you describe the LED behavior on the sensor after you press the Reset button?

Thank you.

3

Hi @Eduardo_Mtz thanks for the quick reply!! regarding our battery alerts, they are triggered when the battery level is lower than 20%. We use the battery level which is a percentage. More in general, alerts are trigged only by analyzing a json message sent by the sensors, which contains in the body said values, see image attached
But the problem is, the sensors didn’t sent some messages regularly and I don’t know why. It seems like we have messages only when a machine is running…

image
image460×519 20.3 KB

4

regarding the antennas, they are secured, not problem in that. Led keeps blinking regularly on “test” light. If i press reset, the blinking stops for a second, then starts again normally. I don’t see anything strange also in that

5

Hi @davidemagno could you attach a video of the LED behavior after pressing the reset button, this will help us to determine if the he Wireless Radio module might be damaged.

6


attached you find the recording. Do you also have any insights regarding the other points that i have highlighted (sensor sending data only when machine is running: is this even plausible or my false guessing? is desk test valid, and if so, how to make it possible?). Please notice that i am not the person who configured these sensors in first place, so i appreciate your efforts and patience

7

Hi @davidemagno thank you for the information. Double blink means device cant talk to the wireless radio module. Could you try a factory reset and share your results please:

  1. Press and release the RESET button
  2. Wait for a second, then press and hold the CONFIGURATION button
  3. Hold the CONFIGURATION button for about 20 seconds
  4. Release CONFIGURATION button
  5. Wait for 3-5 seconds
  6. Press and release the RESET button

Thanks.

8

Hi @Eduardo_Mtz so i did the test twice but still double-blinking. Is there something i may missing?

9

From what it looks like, it seems as if the sensor’s CPU is unable to communicate with the XBee/868MHz RM.

10

Hi @davidemagno do you have another sensor nearby that we could use for a quick test? I would like to swap the wireless radio modules between the two units to see if the issue follows the radio