MirPro 4-20mA channel interference?

Hardware
1

Hi, I just recently got the mirpro MP44_20_SET radio transmitter and receiver of 4x 4-20mA channels. Everything is working now, but the sensor channels are affecting each other. If I am applying pressure to the pressure meter, the next channel (temperature) also increases for the same amount of time and vice versa. I have confirmed this by monitoring the actual mA-values of the Sender device. If the channels are affecting each other, the measurements unfortunately cannot be trusted. What can cause this?

Thankful for help

Edit: channel 4 is seemingly unaffected by the other channels, continuously stable, whereas channel 1-3 all seem to be slightly affecting each other, when one is high the others will drift up too. I tested only with the pressure sensor for each channel, and even the unplugged channels (1-3) had the same behavior when pressure was applied.

2

Hi, are you using the same power supply to power up loop one and opp 2 devices?
try with two diff power supplies.

3

Yes, currently the mirpro sender is giving power to the loops - how do you suggest to use two different power supplies? Thanks!

Please note I added an edit to the original post with some more info

4

Sorry, i was talking about power on 4-20mA output side.

5

Ah ok, that side seems to be working well from what I can tell…

6

So which side is the issue?
They both should have the same issue if there is any issue. They mirror each other.

7

The device that is the radio transmitter, aka the device that have my sensors connected to it. I am connected to it with wifi monitoring the mA levels and that’s where I am noticing the interference phenomenon. The problem I assume is in the host and the other side just copies.

8

let’s do this

  1. connect a sensor on input one
  2. measure mA on the output device ( on chn1 and ch2)

Thanks

9

Hi Bhaskar,

Ch 2 drifts up approx 0.05mA when Ch 1 is at full scale. Ch 1 has the sensor connected to input and Ch 2 is unplugged.

Example (readings from output device)
No pressure applied to sensor
Ch 1: 4.00mA
Ch 2: 0.35 mA

Max pressure applied.
Ch 1: 20.00 mA
Ch 2: 0.40 mA

Ch 3 also exhibits the same increase, whereas Ch 4 is unaffected.

10

So, if no ideas what’s causing this these devices can be returned? Thanks

11

The values below 4mA are dead band values.
The ADC input has a common power supply. it might be causing this noise. this does not affect the device’s functionality.

12

Thanks for the reply, this also happens with values over 4mA, up to 1% increase of whatever value is being measured currently. Any chance you can confirm this also happens in other devices?

13

The analog parts tolerance is +/- 2%. It will be quite impossible to build two units to output identical signals.
All units will showcase this behavior.

14

The mirroring of the signal is working quite beautifully actually, the problem is in the input device where one channel is affecting the next. Anyway, if it can be fixed in the future I will be a customer again.