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Assemble the probe and mount in can Now you'll need that bit of wire. You'll need a soldering iron or a friend with one as well. Cut the wire so that when it is stuck in the connector as shown, the total length of both the brass tube and wire sticking out past the connector is 1.21". Get as close to this length as you can.
The following is taken in full from Section IX. Optics, Heat, and Electronics; Chapter 3.