At 09:01 AM 12/7/01 -0500, Sherpa wrote:
>Platinum RTDs are cheap these days and are very stable, but they need
>lots of amplification.
>Thermocouples are very robust and new chips make compensating them easy,
>but they don't have the high accuracy of platinum.
>
>What accuracy and stability do you want?  Look at Analog Devices' web
>page (www.analog.com) and search for "thermocouple".

All of these methods are overkill for a "temperature-controlled heat gun".

Why not just use the resistance of a nichrome wire in the exhaust? This is
an acceptable substitute for platinum.

A thermocouple would also work (any two metals, e.g., nichrome+copper,
copper works up to 400 C = 752 F).

Commercial thermocouples are accurate to +/- 1 C = 2 F, but absence of a
cold-junction compensation would expand that to +/- 10 C = 18 F perhaps.

Remember that 1% x 400 F = 4 F, so extreme accuracy isn't required.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ral@lcfltd.com
Least Cost Formulations, Ltd.            URL: http://lcfltd.com/
824 Timberlake Drive                     Tel: 757-467-0954
Virginia Beach, VA 23464-3239            Fax: 757-467-2947

"Vere scire est per causas scire"
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