Oven-controlled temperature stability

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< Analog Electronic ~ Oven-controlled temperature stability

eric

Posted: Thu Oct 05, 2006 11:47 pm Post subject: Oven-controlled temperature stability

Site Admin Joined: 01 Jan 1970 Posts: 311

G. Kleine
Accurate measurements that are not affected by ambient temperature
may be taken when the part or circuit being tested is placed
in an oven whose inside temperature is held constant after a short
warming-up period. This works very well, indeed, when the tem-
oven-controlled temper0atu6re0
stability
perature inside the oven is held
higher than the maximum ambient
temperature. This is
because the inside of the oven
may be heated but cannot be
cooled. This type of control is
frequently used to stabilize a
crystal oscillator or a surface
acoustic wave (SAW) filter.
The circuit consists of a
heating element, R14, which is
thermally coupled to temperature
sensor IC3. The output of
the sensor at 75 °C is +3.48 V,
which rises linearly at a rate of
10 mV °C–1.
Integrated circuit IC1 comprises
an operational amplifier
(at pins 5, 6 and 7) and a comparator
(at pins 1, 2 and 3). The
op amp is arranged as a ×100
amplifier and delivers an error
voltage that depends on the difference
between the actual temperature
and that set with P1.
The preset can set the wanted
temperature between +55 °C
and +105 °C. The stable voltage
across potential divider
R5-P1-R6 is 4.096 V, which is
provided by reference voltage

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