Temp Control issue

Hi again guys,

I have this system where I need to monitor/control 24 incubators.

Most have reasonnable Setpoints and margins of error, thing like 40°C± 2.0°C

The problem I have is that some of them have a Setpoint of 4°C while the margin of error (read diff. Alarms)is ±0.2°

This 0.2°C really bugs me.

I can have RTDs or even TCs with 0.1C resolution but the input modules for PLC add more error than I can live with.

My typical RTD would have a resolution of 0.089°C but the darn input cards don't match this.

Normaly its not a problem when we read something in the hundreds of degrees but at 2°C its BAD!

Do you guys know of converter modules (Ex: ModbusTCP) that can accept a 100 Ohm RTD (3 Wires) that are not crazyly expansive?

Know I'm at $350 a point for a 0.01 resolution and $200 for 1°C ...

What I need is a cheap way to read temperatur from -10 to +50 C ±0.01°C and bring it into a PC with a SCADA.

24 times.

Any suggestion is welcomed.

I'm not sure of the resolution, but DGH Corp and Advantech have analog and temperture modules that communicate over a serial link (I thihnk with Modbus RTU). You might check them out.

Hi Pierre

A similar question was asked recently and I suggested a look at Red Lion Controls Modular Controller. This controller / Data acquisition system has a resolution of 0.1c and can communicate with a number of PLCs and I beleive with a PC over ethernet. It can have upto 16 modules with 4 or 6 inputs on each module.

Red lion's web site is www.redlion.net

Jim.

You may try Omron from the initial search temperature input modules
D2t1-tso4p
or qt1-tso4t or 4p

both of them had an accuracy of 0.1 c or 0.3%

I have seen many x-mitters and what could be the most accurate for me is not to go through a PLC but directly into a PC with the x-miter com. ...

Its only that I need 0.01 C precision ...

...and most x-mitter altough they have an ana analog resolution of 15 bits and more ... they have a digital resolution of 8 bits. ... firmware vs packet size stuff I figure!!!

Still searching to get 0.01C not % into my PC the cheap way

I will check out those leads thanks.