Joined on 05-02-2008
remote data logging for a water treatment application
I'm looking into setting up a basic remote monitoring/data logging system. Inputs I would need to monitor are pH, conductivity, and flow rate. I'm thinking of the snap pac system, but I have a few questions, namely:
- Why is there a controller module and a "brains" module? Would I require both?
- I would like the ability to display data at the site; something simple like an lcd text screen. Can I get a 3rd party text screen to interface with the system (the Opto terminal is overkill)?
- I like the ph/ORP analog input; is there anything specific for conductivity?
Any help or guidance would be greatly appreciated!
05-06-2008, 7:29 AM
Joined on 12-01-2003
Optomation Systems, Madrid, Spain
Re: remote data logging for a water treatment application
Sounds like another perfect application for PAC. In answer to your questions
SNAP-PAC-S controllers are really for larger applications or where there is a lot of distributed I/O to be processed in a single processor. But it sounds like your application is much more orientated towards a single SNAP-PAC-R processor. This contains a programmable controller environment more then sufficient for your needs.
If you plan on totalizing high speed digital pulses you may need the SNAP-PAC-R1 processor, if not the SNAP-PAC-R2 will do.
There also exists a lower cost SNAP-PAC-EB brain with some event/reaction capability. If you really only need remote data acquisition and access without any local processing this could be sufficient, but my advise would be to spend the difference and go for a SNAP-PAC-R processor from day one. You wont regret it.
From within the programmable language PACControl, you can easily write programs to interface to any RS232 LCD display to transmit ASCII data to its screen and receive input data form the operator such as access code, setpoint change, menu request etc. A four line LCD ASCII display is probably enough. Many customers use a low cost QSI Terminal QTERM-J10 and Opto22 can supply you ready-made subroutines for interfacing to it.
If you don't plan on using the built-in RS232 port (Green connector on the top) for a modem connection, then you can connect a display to this comport. If you are planning a modem link, then you will need to buy a SNAP-SCM-232 module for the rack SNAP-BxM where x is the number of modules you plan on using.
For a conductivity input, you can use any suitable conductivity transmitter (try googleing for suitable suppliers) and then use the corresponding SNAP analog input module, usually 4-20mA, or 0-10V. Probably one of the spare channels on the modules you already need will do or you could consider a 4 channel input module.
One of the main questions for remote data logging is how to connect. SNAP PAC controllers allow PPP modem connection allowing GSM, GPRS & 3G mobile links, local or extended network, connection to Internet via a router, or even a wireless router. Check with your phone company for available options in your area.