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CT255 • 24
USE OF YOUR COMPUTEMP 255
Now we are ready for the moment of truth, the initial power up and running of
your binary thermometer. Energize the unit with a suitable 7.5 to 12DC power
supply (noting that the center pin of the power supply is the positive connection)
and watch your thermometer count up the first of many times. After a few sec-
onds the display should reset and re-count to the current temperature. You can
verify that the sensor is working correctly by pinching the temperature sensor
U3 with your fingers and watching the temperature increase to about 98 de-
grees.
Remember, that marvelous National Semiconductor IC give a precise tempera-
ture/ voltage output, so no calibration is required. Sure saves some effort! The
original kit required an ice-water bath for the sensor, and any non-linearities in
the response of the diode curve were not easy to rectify.
Find a suitable location to display your latest achievement, and enjoy the fact
that you did it yourself, and you learned something along the way! That’s the
real kick of kit building; you know what makes it tick.