temperature sensor network

[embeddedfactory]

Hi: I am new to the forum, I am Alejandro from Argentina. I was asked to build a low cost temperature sensor network.
The network will have 10 sensors separated 10 meters each.

I would like to hear your opinion about the technology to use, I know that 4-20 mA sensors are suitable but very expensive, 1-wire sensors can be an option.

Do you know any other low cost solution?.

Thank you in advance,
alejandro

 

[Skogsgurra]

Hi Alejandro,

One of the cheapest sensors you can use is a thermistor with a negative temperature constant (NTC). They are small, they are cheap (a dollar apiece - or less), and they are non-linear.

They can be linearized with a series/parallel resistor over a limited temperature range (say -20 to +30 degrees, or 0 to 50 degrees) if you need that. If you evaluate the temperature with a computer, you can linearize in the computer program and the temperature range can then be more than 100 degrees celsius.

Google "NTC thermistor" for tons of more information.

 

[embeddedfactory]

Thank you very much for your help.

I do understand that NTC can be a cheap solution.

I was wondering how can I reach a CPU (for instance, a PLC) with that information (the measured temperature). That is to say, how can I "send" that temperature to a PLC that is 10 meters away from the sensor.

That is why I was considering 4-20mA and Dallas' 1-wire as options.

Best Regards,
Alejandro

 

[vanoorta]

Use the Barix BarioNet controller (

http://www.barix.com)

with the Dallas 1-wire sensors. With a small extension module, the controller can connect to as many as 16 of these sensors for something like $400 total. The controller can log data locally, display dynamic values on its built-in webserver, send data to a server, etc...

 

[harkdog]

This is not to promote a given product - I have not used this equipment. Acromag makes a din mount module that takes 24 VDC for power and you can communicate with it with ethernet, modbus RTU, or other medium/protocol. Just find one your PLC supports. The RTU unit can be found at

http://www.acromag.com/models.cfm?Product_Function_ID=28&Category_ID=13&Group_ID=2