David,
Thank you for that correction.
In addition, I left out these 2 paragraphs,
the second is critical for proper WCC103 sensor replacement.
The Weller WCC103 temperature sensor is actually an iron-constantan
thermocouple
(possibly a Type J). Weller used Type K thermocouples for its ECxxxx
soldering station series.
Sensitivity believed to be about 50 µV/°C
The relationship between temperature and voltage produced is NON-Linear.
When replacing the WCC103 sensor the leads MUST be correctly installed
OR the soldering iron stays on continuously and eventually overheats.
The Iron (magnetic) lead connects to the RED wire
The Constantan (copper-nickel alloy/non-magnetic) lead connects to the
YELLOW wire
What is a thermocouple sensor?
A thermocouple is a sensor for measuring temperature. It consists of two
dissimilar metals, joined together at one end. When the junction of the two
metals is heated or cooled a voltage is produced that can be correlated back
to the temperature.
http://www.omega.com/temperature/Z/pdf/z021-032.pdf
gb
----- Original Message -----
From: "David Woolley" <[EMAIL PROTECTED]>
To: "Elecraft Reflector" <[email protected]>
Sent: Sunday, December 30, 2007 4:30 AM
Subject: Re: [Elecraft] Weller WCC100
WCC103 temperature sensor has a resistance of about 1 to 2 ohms at room
temperature (27 C)
Thermocouples are voltage source devices, not variable resistance devices.
With thermocouples, you get the difference in the voltage between the hot
and cold junctions, so, for really accurate operation, you need some other
mechanism for measuring the cold junction temperature. In this case, the
variation in cold junction temperature and required accuracy might be low
enough that simply assuming 25C is good enough. Whether cold junction
compensation is included is a significant feature of the design.
--
David Woolley
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