cornbread
Lifetime Supporting Member
Looking to add a some temperature transmitters (loop powered)for some control cabinets .. tracking and alarming. Looking for a cheap xmitter. Any help would be greatly appreciated.
Temperature transmitter cheap
- Thread starter cornbread
- Start date
Why not just twist some Type-J Thermocouple wire together and use that to measure the cabinet temp - can't get much cheaper than that.
http://www.ti.com/lit/ds/symlink/lm35.pdf
Depending on supplier and type (housing and so on) the LM35 costs about 2€ a piece. I don't see anything cheaper than that for the moment.
Kind regards,
Depending on supplier and type (housing and so on) the LM35 costs about 2€ a piece. I don't see anything cheaper than that for the moment.
Kind regards,
Tom Jenkins
Lifetime Supporting Member
I wouldn't use a T/C at that range, but you can get RTD inputs for many PLCs and use an RTD.
Another option is http://www.dillinstruments.com/Products.html
I've had good luck with their RTD in 4-20 mA output, and they also have voltage outputs.
Another option is http://www.dillinstruments.com/Products.html
I've had good luck with their RTD in 4-20 mA output, and they also have voltage outputs.
I know RTD's are better at that range but you have to buy one of those. TC wire twisted together will measure enclosure temperature very well and costs almost nothing. I've done this dozens of times.
danw
Lifetime Supporting Member
For a panel temperature reading, there might be something cheaper - bare copper wire, or the CJ value of an existing thermocouple input.
Using a length of T/C wire assumes that a direct-connection T/C analog input is available. A direct-connection T/C input requires cold junction compensation.
A piece of bare copper wire across the thermocouple input terminals will produce the cold junction temperature (the temperature of the input's connection terminals) measurement as the value for that input.
Some devices will report CJ temperature of an 'in use' T/C input as a useable, taggable process variable, so an 'additional' input point might not needed for a panel temperature reading.
Very true. The equipment I typically use has cold junction compensation and the bare wire across the inputs will display the cold junction temp.
The length of T/C wire, however, allows the technician to choose where to measure the temp rather than right at the cold junction compensator at the input module.
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