4-20 ma measurement with beaglebone black

[bali...@gmail.com]

Hello, 

I am wondering if a beaglebone black can be used to measure industrial 4-20 ma loops?  I see there is an ADC feature, but the voltage range is only to 1.8V.  Is it possible to set it up to work with the standard 24VDC circuitry involved with most 4-20ma loops?

Thank you in advance, 

-JP

[evilwulfie]

opamps are your friend

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[Przemek Klosowski]

 On 8/17/2016 5:26 PM, bali...@gmail.com wrote:

I am wondering if a beaglebone black can be used to measure industrial 4-20 ma loops?  I see there is an ADC feature, but the voltage range is only to 1.8V.  Is it possible to set it up to work with the standard 24VDC circuitry involved with most 4-20ma loops?

A 90 ohm resistor carrying 20mA will develop a voltage of 1.8V. This is cutting it a little close, so I recommend 68 ohm, which is a more standard/easier to find value anyway. So, just terminate your 4-20mA line with this resistor, and connect it to the Beaglebone analog input. Of course if you're in an industrial environment you need to watch out for transients, noise and interference, especially since the Beaglebone inputs are famously fragile, so include some serious input protection (e.g. four diodes connected as two anti-parallel 2-diode chains, with a filter cap across it and maybe some series resistance). Then again, you could follow evilwulfie's advice to use a dedicated buffer op-amp.

[Graham]

If you would think to Google "4-20 mA receiver" you could learn a lot.

Peripheral IC's from TI and Maxim that have most everything you need all ready designed in.

Modules you could interface to the BBB, etc.

Application notes on how to design receivers, and things to worry about, common system problems that people have had with this circuit for the last 50 years.

Good luck.

==

[drhun...@gmail.com]

There is a TI reference design for 4-20mA loop interfaces http://www.ti.com/tool/tida-00550. It is designed as a cape.

Iain

[robson...@gmail.com]

Hi

As I am also working on beaglebone to measure 4-20mA sensor output with  Receiver module using less power

can anyone help me out with code to interface the 4-20mA current loop Receiver with beaglebone please ??

[Caarloss]

Hi, I'm designing ESD protections to 4-20 loop interface on Beagle Bone analogic input. which is the clamp voltage of any TVS zener that i could use? Thxs