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
On Thursday, August 18, 2016 at 4:24:45 PM UTC+1, Graham wrote: > > 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. > > == > > > > > > On Thursday, August 18, 2016 at 10:03:12 AM UTC-5, Przemek Klosowski wrote: >> >> On 8/17/2016 5:26 PM, [email protected] 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. >> >> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/33e62589-6e59-4eac-8971-a59e6d0d832c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
