Just about to place the order for the PID and was wondering if anyone uses the K Type thermocouples. Do you find them to be not that accurate? Its hard to drop $65 for 2 RTDs when K type go for less then $10 on ebay.
THANKS! Dont know how I missed those searching this morning.
excerpted from here
Selecting sensors for reliability
For temperatures ranging from cryogenic to about 800°F (427°C), a resistance temperature detector (RTD) is better than a thermocouple. Though RTDs were once more expensive, today the cost difference between the two is negligible, and an RTD provides greater accuracy, stability, and life span. Over its useable range, a standard-grade RTD provides more than twice the accuracy of a thermocouple.
To understand why, consider the materials of construction. A thermocouple is comprised of two dissimilar metals welded together; the resulting junction begins to deteriorate immediately. The deterioration is faster at higher temperatures and can result in drift of several degrees per year. On the other hand, an RTD consists of stable, highly purified platinum.
RTDs drift just fractions of a degree per year and are accurate for many years when used at temperatures below 800°F (427°C). Thermocouples, however, are not and require frequent replacement. This tips the scale for installation costs in favor of the RTD.
ace, you can use a compression fitting to mount the probe. something like http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053
I think I am going with the RTDs for the following reasons:
1. I'm anal and strive for perfection and the RTDs are more accurate.
2. The Auber Instrument RTDs have the nice quick disconnect to remove the wire. (even though they are charging me $18 to ship something that would easily fit in a $10 USPS box).
I plan on using 1 PID and having the quick disconnect I could swap the wires from the HLT RTD to the RTD on the boil pot.
You can get liquid-tight RTDs for under $10 on ebay, too:
http://cgi.ebay.com/Thermocouple-Te...528?pt=LH_DefaultDomain_0&hash=item3cb7542018
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