California Instruments’ 850T Series variable frequency
oscillators and 855T Series fixed frequency : oscillators
are designed to plug into and derive their ; power from any
of the Invertron® AC Power Sources. ' The output of the
oscillator then provides the input frequency and amplitude
drive for the Power Source. They employ digital logic
techniques for frequency generation with a crystal
controlled oscillator serving as the reference for the
digital logic circuits. This technique provides long term
frequency stability not obtainable with analog circuits. The
850T Series has three frequency ranges selected with a front
panel switch. There are four frequency selection controls, :
permitting precise adjustment of the output frequency with
resolution of one part in ten-thousand. Frequency is
adjustable in 0.01 Hz steps from 0.01 Hz to 99,99 Hz in the
XI range, in 0.1 Hz steps from 0.1 to 999.9 Hz in the X10
range and in 1 Hz steps from 1 : to 9999 Hz in the X100
range. By setting the internal switches and making other
minor internal changes to < the 855T, its output frequency
may be similarly ad- ' justed to any frequency selectable in
1 Hz steps.
,The crystal oscillator reference has an average frequency
stability of five parts per million per degree Centigrade.
Thus, with the frequency having been set at room
temperature, the maximum variation^ would j be ;
approximately 125 parts per million (0.0125%) oyer the 0 to
55°C range.; The oscillatorfrequency is divided by digital
logic circuits to the selected output frequency and then
filtered to remove harmonic components.
The 850T/855T Series Oscillators will shut down if ; the
frequency is outside of factory set limits. This ; prevents
selection of ;a frequency outside the operating limits of
the associated power source, in the case of the 850T, and
protects against a malfunction of the oscillator circuits
that would produce a frequency outside these limits.
The 850T/855T Series Oscillators are equipped with ■ a “soft
start” feature that slowly increases the output ; amplitude
from zero to the set level unit is first turned on. The 850T
also “soft starts” when resuming operation after automatic
shutdown caused by selection of an out-of-limit frequency.
Both the 850T and 855T Oscillators may be equipped with
optional circuit boards to provide two- or three- phase
outputs. Additionally, the output phases may be set to any
30 degree increment relative to the reference phase. Because
of the digital techniques employed, the electrical angle
between phases remains constant irrespective of frequency.