OT temp sensors

[2004sk4]

What is the best way to read temperatures of machine cabinets to be displayed remotely

The plc will be a compact logix(remotely mounted) and point i/o ethernet module(one per set of machines would be nice) as this will be eventually a 22 machine project.

The sensor i have been thinking about.
temp sensor which outputs 0-10 or 4-20 to a analog plc card
thermocouple the a tc plc card reads

The location of the sensors will be spreadout on the machine
The machine is 20 feet tall 20 feet wide and 15 foot deep.


I have 3 cabinets 1 main motor 1 gearbox plus temp of the building for reference


What products(brands) do you recommend or have experience with.

Thanks ahead of time

 

[KP_EENG]

There are several ways to do this. One way is like you said, mount a TC or RTD sensor in the panel and feed this to a TC or RTD transmitter. The transmitter will typically produce a 4-20 mA output which has better noise immunity and can be transmitted over longer distances than the 0-10 V signal.

Another way, which would actually give you local temperature displays as well, would be to use a stand alone temperature controller with a 4-20 mA Re-transmit output. The TC or RTD would be an input to the controller and the 4-20 mA Re-transmit output would provide the signal to your PLC analog input. Most of these controllers have a readout of the process variable which would allow you to see the panel temperature locally.

Either Watlow or Omega Engineering can provide TCs or RTDs, Transmitters and controllers. Automation Direct also offers some low-cost temperature controllers.

Regards

 

[val_99]

I'm not sure if RTD or T/C modules available for point I/O, but that would be my choice. Basically remote I/O with RTD modules, so I wouldn't need extra temp. transmitters. RTDs would be directly connected to modules. All scaling done through PLC (one more reason to eliminate temp. transmitters). My personal preference is RTDs. Even it is slightly slower then Thermocouples, but much more robust and accurate. Just run 3 conductor cables from your RTDs to remote I/O box. That all.

 

[TConnolly]

If you have a TC card for other inputs already then there is no need to add any internal cabinet sensor at all. The TC card contains a ultra precise thermistor to measure the temperature at the terminals of the card for CJC. The CJ temperature reading can be accessed by your PLC program or any HMI attached to it.

 

[2004sk4]

Thanks for the replys

Point i/o has both rtd and tc modules that are limited to 2 points per card. I would like to use just the inputs to the plc with a touchscreen. Although the meter idea would work it would add alot of cost to the project.

The system i am working on will monitor temps
control the humidifiers
control the antistat bars
control lighting during no use
display hour meter info
display raw material data for
changeovers

This is the original list but i am sure more will be added

What is the main difference between a 1768 and 1769 processor

 

[Lancie1]

2004sk4,

You said that eventuallly there will be 22 machine, with temperature monitioring on each machine. How many temperature inputs do you estimate that each machine will need? 20' x 20' x 15' is a large volume. Are these machines presses? Is this monitoring to detect hot spots on the machine? How far from each machine to the CompactLogix Remote I/O?