PLC experts (ph Questions)

[windgod]

was wondering if they made a PH and Orp (bnc) type input for plcs out there, was looking at a automation direct 205 unit it seems to be the best as far as user friendly, would appreciate input

Thanks
Rick

[Mr.Biggs]

Generally ph probe is connected to a transmitter and the transmitter is connected to a 4-20ma card or 0-10v card depending on transmitter.

http://www.omega.com/ppt/pptsc.asp?ref=PHTX014&Nav=gredd05

this is a 4-20ma transmitter

[slug]

Ebay is your friend. I built a circuit for ph/orp probes but then I bought an omega transmitter with lcd display for $9, and it's hard to beat that.

Also: http://cgi.ebay.com/MODEL-PHMA-2-WIRE-TRANSMITTER-VYNCOBOX-JUNIOR-NEW_W0QQitemZ7559277544QQcategoryZ78182QQssPageNameZWD1VQQrdZ1QQcmdZViewItem

Which is really this: http://www.sensorex.com/support/specifications/download/pHMASpecs.pdf

1 left, I bought the other 2 :)

[slug]

Also, if you can't read 4-20ma (I can't) you can just jumper it with a resistor to get volts. Volts = Current * Resistance

[easttn]

PLC full system (http://cgi.ebay.com/Siemens-S7-200-CPU214-System-W-3-Expansions-Modules_W0QQitemZ160024430340QQihZ006QQcategoryZ97184QQrdZ1QQcmdZViewItem) available here. Good price. Not mine, I don't know the guy.