4-20ma IoT Long Range Wireless 4-20mA Current Receiver Power Question

When I hook up this NCD device and run it on battery, I get valid values (after scaling, for a 4-20ma temperature sensor, Optex SA-80T-2A)

However, when I try to add barrel jack power adapter to the NCD device, so I dont need to use batteries, the values go all wonky.

I tried with the Jumper in both positions, which position should it be in?
It seems that the barrel jack power adapter for the sensor is interfering with the mA readings?

I am using a 12V, 1.5a adapter, to power the 4-20ma NCD Receiver, same one that comes with the MQTT Gateway.

Just a bit more information. I am using Node-Red to scale the mA reading it gets from the NCD device, on a scale of 4-20 ranged to 32-392.
When I multimeter on the Phoenix connector terminals that the sensor uses to plugin to the NCD device, I get nice stable mA values.

while using external power the jumper needs to be opposite to “–” marking.
how is the 4-20mA sensor powered up ?


The 4-20ma Sensor is self powered, and has 4 wires coming off of it, marked as…

The brown and blue wires are connected to a 24V power supply.
The black is connected to the + on the NCD 4-20ma Receiver.
The grey is connected to the - on the NCD 4-20ma Receiver.

Thank you for confirming the jumper setting, ill play around with it a little more and see if I can figure out something new.

will you be always using it with external power ?

if you are there is solder pad jumper SJ1 near the 4-20mA in put screw terminal. You can bridge it and it will consume more power ( shouldn’t be an issue if its used with external power) but it will add one more noise removal layer.


Hello Bhaskar,

We bridged the solder pad as recommended. Although there may be a slight difference in the amount the mA output jumps from reading to reading, the reading are still unpredictable and vary as much as 10 mA once the 12V power adapter is connected.

The jumper is in the correct setting and we are using a 4-20 mA current generator so as to eliminate variables that a sensor or loop power supply could introduce.

We have 2 NCD Current Receivers, both output correctly under battery power, both output incorrectly when the 12V power adapter is connected.



Hi Mark,
I ran some test with external power supply as well.
Here is what i did

  1. Tested everything with on board a battery
  2. with BK precision power supply
  3. 12V wall adapter
  4. BK precision power supply with a pump

In all cases the current readings were almost constant. I am attaching my results.

Can you share the part number of the supply you are using in your test ?

I used this to generate 4-20mA signal

attaching my test results.
there are some zero there… that when i turned off the loop simulator to see if it reads anything when no sensor is connected.

cur1.xlsx (1.5 KB)

Thank you for looking into this.

We are using a UCTRONICS 0-10V 0/4-20mA Current/Voltage Signal Generator Part Number U6206. I have used this generator with PLC input cards and our Siemens IOT boxes without issue for sometime. We have an electronics repair center here in-house. I just walked over and had it checked. The current and voltage outputs measure correct and are consistent.

Output voltage from the adapter measures 12.12 vdc.
We also did a sanity check using the same sensors, same wiring, power supplies, current generators…etc with other hardware without issue.

mA output variance with batteries averages = .12024 mA
mA output variance with adapter averages = 7.97 mA (varies depending on sample size)
I do see a correct value on occasion but random.

It has to be something simple but its kinda hard to wire a current generator up incorrectly and theres only one jumper to move so I am at a loss.

will is be possible to use one of these wall adapter to test ( honestly i am not sure what could be causing this).
do you have one of these wall adapter power supply we send with some of our products ?
i tested with this and didnt see any issue with readings.

can you share the raw ADC values as well.

Kyle sent you an email with the results collected with a sensor connected and with the current generator connected and set to 4.0 mA. He used lab view to collect the results.

Thank you again for your help.

I will build 3 samples over here and repeat the testing.

Can you send one unit over here, that will make debugging bit easier for us.

Hello Bhaskar,

It appears we have discovered the root cause. Within our corporate facility we have a large repair lab. In the repair lab we have several large drives and AC/DC motors running that we use to test repaired items before they leave the repair center. What we have discovered is that we have a bunch of noise and errant voltages coming across the buildings ground.
This is a very large facility with a ton of circuits. Its more than likely that we have various neutral issues as well from moves and building/lighting upgrades done over the years. Those issues combined with numerous drives, power supplies, large HP motors and so on are creating a ton of power related issues. When using an external power supply with a 3 prong plug we are introducing those issues into the sensors. Isolating or just removing the ground wire from the power supply’s used to power the sensors and the Current Receiver took care of the issue all together.

Thank you for your help.


1 Like

Hi Mark,
Glad you got it working. It was sure a learning exp.

We have a new 4-20mA product coming ou in next few days.

  1. it will support 6-32V AC/DC input
  2. 16 bit ADC resolution
  3. On board power switching power supply ( it should take care of the noise issue you were having)
  4. Will come in IP65 box

4-20mA is one of my favorite protocol.


Hi Bhaskar does this component is ready to buy?

This product is live now