California Instruments 846VM Oscillator
California Instruments’ Model 847T
is designed to plug into and obtain power from
all of the Invertron· AC Power Sources. Frequency and
amplitude are remotely programmable through an IEEE-488
connector or through a parallel Interface
connector. Both connectors are mounted on the rear of the
associated power source and connected to the 847T
multi-conductor cable. Parallel programming by the parallel
connector of the 847T
is always available when the
GPIB relinquishes control or allows the system to go the
local control mode. If the 847T
the parallel Interface
input at the 846CM is disabled.
The output of the Model 847T
provides three- phase variable
frequency and amplitude drive for the power source. Remote
inputs sense the voltage across the load connected to each
leg of the power source. In response to the level of these
inputs, the servo systems adjust the individual outputs of
to maintain the voltage across the power source
load at the programmed value. The 847T
employs digital logic
techniques for frequency generation with a crystal
serving as the reference for the
digital logic circuits. This technique provides long-term
frequency stability not obtainable with analog circuits.
is capable of operating from 45 Hz to 9999 Hz over
three ranges; 45 to 99.99 Hz
(selectable in 0.01 Hz steps), 45 to 999.9 Hz (selectable in
0.1 Hz steps) and 45 to 9999 Hz (selectable in 1 Hz steps).
The low end of the frequency detector is adjusted to shut
down the output of the 847T
when the selected frequency is
below 45 Hz. The high end is factory adjusted to the upper
limit of the associated power source. Extending the
frequency range beyond 5 KHz requires programming with an
internal jumper. A "soft start" feature is incorporated
which gradually increases the output amplitude at initial
turn-on and when operation resumes after a shut down caused
by programming an out-of-limit frequency.
The output voltage range of the Oscillator
to the amplitude programmed for the associated power source.
When the programmed output voltage for the power source is
135 or 270 volts, the Oscillator
output will be in the range
of 4 to 5 volts rms. The precise level will be dependent
upon the voltage level at the sense input. The sense input,
when connected directly across the load, increases the
output (and the power source output) to
compensate for any drop in the lines connecting the power
source to the load.
Relative to the reference phase, Phase A, the angle of the
Phase C output may be internally preset to any thirty degree
increment. Because of the digital techniques employed, the
electrical angle between phases remains constant
irrespective of frequency.