Creating 4 to 20MA ?

[Ioannis]

Steve is a magnet for accidents. Hope he is doing much better now after testing how strong a car is...

Ioannis

[Luciano]

Hi,

4-20mA Current Loop Primer:
http://www.murata-ps.com/data/meters/dms-an20.pdf

Best regards,

Luciano

[mat janssen]

Here a schematic diagram I always use when using pic pwm and analog out.

[amgen]

thankyou for links which I read all.

Would like to make PIC ckts to output the 4-20 MA stuff.

what I know (maybe), recieve ma. is easy, just read V across a 100 to 250 ohm resister and scale/calculate or limit the a/d reading. PIC can do 10 bit but many products reach to 12 or 14 bits.
Send or creating ma signal seems a little more involved, apparently needed is 12 to 24 vdc supply to be able to adjust for wire and other loop resistance ??
Getting a good DC level (0 to 5) volts from PIC with 1000 or more resolution --- not so easy. See diagram, and how to set limits of 4 and 20 ma with resisters ???
.
.
.
motor t-stat
used simple process of elimination (mental process that is) the 2-A and F wires are generally all thats needed to run motor in both directions and more times than not, two small wires will be for temp sw.

don

[Luciano]

Hi,

See this link:
http://www.maxim-ic.com/appnotes.cfm...te_number/722/

Best regards,

Luciano