Distributed Thermocouples

J

Thread Starter

Jeremy Pollard

Hey all. Looking for an inexpensive way of connecting 24 or so thermocouples or RTD's to monitor building temp in a large warehouse environment. Nothing fancy required. Any comments? I know I can use Momentum I/O or Ethernet I/O or some other industrial bus network. Hoping I've missed something
Thanks in advance

Cheers from:

Jeremy Pollard, CET
[email protected]
On The Web - http://www.tsuonline.com
PLCopen North America - [email protected] www.PLCopen.org
the Training Factory, Inc.
Programmable Controller Support Systems
The Software User Newsletter ONLINE
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8 Vine Crescent, Barrie, Ontario L4N 2B3
705.739.7155 Fax 705.739.7157
 
J

John Thornton

I'm looking to do the same thing using HVAC thermistors. If you find out how let me know. If I find anything I'll let you know.

John
 
C

Curt Wuollet

Perhaps an inexpensive DAQ card in an old PC? This many analog inputs for a PLC is pretty expensive. Or 1 analog in and a multiplexer. I'm sure some of the datalogger companies would have
something, but inexpensive is hard to come by.

Regards

cww
 
R
If using a PC and a DAQ card, Omega sells
a bunch of types at a pretty reasonable cost.
All you'd do is write a little program, say
in VB using Omega's software that comes with
the card to read the card's points.

That's the simplist and most cost effective way
if all you're points are really close to each
other. If not, then yeah, go with some sort of
distributed IO scheme like your Momentum/Ethernet
IO and bring it into the PC.

Good Luck!!!

> Hey all. Looking for an inexpensive way of connecting 24 or so thermocouples or RTD's to monitor building temp in a large warehouse environment. Nothing fancy required. Any comments? I know I can use Momentum I/O or Ethernet I/O or some other industrial bus network. Hoping I've missed something
> Thanks in advance
>
> Cheers from:
>
> Jeremy Pollard, CET
> [email protected]
> On The Web - http://www.tsuonline.com
> PLCopen North America - [email protected] www.PLCopen.org
> the Training Factory, Inc.
> Programmable Controller Support Systems
> The Software User Newsletter ONLINE
> The Crazy Canuckian!
> 8 Vine Crescent, Barrie, Ontario L4N 2B3
> 705.739.7155 Fax 705.739.7157

 
J
I did this on a project with 12 T/Cs per floor and three floors using a cheap(er) output card to power up transmitters connected to
bent-wire thermocouples.

The output card fires the + side of each transmitter at 4 second intervals and then averages the analog signal coming back to a single
analog channel on a PLC. This way I'm duplexing the analog channel with a 16 or 32 point output card vs. a expensive multiplexer. All of the
transmitter commons are connected together on a terminal strip, and the seperate tranmitters only fire when the correct output is energized.

I don't think is a exteremly accurate way of meausurement but it worked for multi-zone climate control.

John
 
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