Cooking Hacks Forum

4-20mA board information
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Author:  Doktora [ Wed Nov 06, 2019 1:04 pm ]
Post subject:  4-20mA board information


I’m running the example code for the 4-20mA bird.

1. Even when nothing is connected to the sensor board the isConnected(CHANNEL) returns true, and voltage and current values are returned -- see bellow for code output.

2. In the online documentation, there is no description what the jumpers are for. Can you please specify?

3. Can you please provide documentation on how to connect a 24V sensor with external supply. I'm using the Arduino/Pi shield connector, so as I understand, it is not possible for the current loop board to supply 24V. My sensor (a water pressure sensor) has two wires (+/-), to what pins should the power supply and the sensor wires be connected?

Author:  libelium-dev [ Wed Nov 06, 2019 1:22 pm ]
Post subject:  Re: 4-20mA board information


1. If there is nothing connected that output is normal, we can't see the output you're talking about.

2. We suppose you're following the tutorial of the Cooking site, ... l-galileo/

In section 1 it says,
"The 4-20 mA Board has 4 input channels which allow converting signals that come with this industrial standard. This shield works with type 2, 3 and 4 current transmitters. Each channel can be configured for working with these types of connections. If the jumper is retired, the receptor will be configured as float (type 4 connection)."

In any case for more deep information of the board you can consult the technical guide for Waspmote. ... l-galileo/

3. It is explained in the tutorial of cooking in section 4.

Hope this information will be useful.


Author:  Doktora [ Tue Nov 19, 2019 10:26 pm ]
Post subject:  Re: 4-20mA board information

Thanks, that information cleared out some questions I had and I got the sensor board running on Arduino.

However, I have problems getting it to work on the Raspberry Pi with the shield (R-Pi to Arduino shield).

I've setup everything except that it is not clear to me how to connect the external power supply for the sensor (since the sensor board cannot provide 24V output when using the R-Pi shield).

Can you please provide an example.

The 4_20_basic.cpp code returns the following when no sensor is attached, which doesn't make any sense:

Int value read from channel 1 : 1297
Voltage value rad from channel 1 : 6.339199V
Current value read from channel 1 : 25.298143mA

Author:  libelium-dev [ Wed Nov 20, 2019 4:46 pm ]
Post subject:  Re: 4-20mA board information


Which sensor are you using? Do you power supply the sensor externally?


Author:  Doktora [ Wed Nov 20, 2019 7:51 pm ]
Post subject:  Re: 4-20mA board information

My sensor is a water depth one like this:

It is a type 2 sensor, so my question is how to connect the power and the sensor to the 4-20mA board? In series? It's the first time I'm working with this board and 4-20 sensors so some help would be great. Maybe it would be easier to work with Arduino, but I need Pi to process the data.


Author:  libelium-dev [ Thu Nov 21, 2019 2:56 pm ]
Post subject:  Re: 4-20mA board information

Please share with us the datasheet of the sensor?

Author:  Doktora [ Sun Dec 01, 2019 9:26 am ]
Post subject:  Re: 4-20mA board information

I'll copy paste what I just got from the reseller:

Power supply: level transmitter power supply 24VDC
Comprehensive accuracy: 1%
Output signal: liquid level transmitter output 420MA / light column display table default relay output
Stable performance: ≤0.29FS
Measuring medium: cold water, no corrosive liquid
Housing protection: IP68
Overload capacity: 150%
Temperature drift: ≤001% FS / ° C
Medium temperature: -20 ° C ~ 40 ° C
The hydrostatic level transmitter sensor determines the liquid level height by measuring the static pressure generated by the liquid level. Formula for hydrostatic pressure
P = Po + PcH means, where: Po is the non-atmospheric pressure on the liquid surface, p is the measured liquid density, H is the liquid level height, G is the gravity plus
Speed ​​(constant). When Po remains constant, the pressure depends on two variables, density and level. When the level density is a certain value
The level will be linear with the pressure. This pressure acts on the pressure-sensing surface of the transmitter's diffused silicon pressure sensor.
The piezoresistive effect converts the pressure of the liquid column into a voltage signal. This signal is directly converted into 4 ~ 20MA after being amplified.
If the atmospheric pressure at the upper part of the liquid surface changes, the pressure sensor will be affected as if the liquid level changes.
YW-136 adopts the design method of ventilating cable to introduce the outside atmospheric pressure to the other side of the pressure-sensing surface of the sensor. Eliminate the cause
Atmospheric pressure.

Author:  libelium-dev [ Mon Dec 02, 2019 5:08 pm ]
Post subject:  Re: 4-20mA board information

Hi, we're but if it's type 2 sensor it can be connected to our board due to the board only can provide 12V power supply.


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