Optical telemetry control and data transfer system Page: 1 of 3
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the freymiBr mwtrtcr ylddt a imiIu train of
0*100 Ub. n» output of the converter drives
ami constructed to control and scatter AuMtitren loo
tourers. Ottk the exception of tor accelerating and
decelerating power nupiltti all other power supplies
and »j pas control that operate ti* Ion source are
elevated to accelerating potential. He telemetry
system operates aot monitors the Isolated power supplies
and transmits data across the Me* voltage oao. Tie
transmission medium is Infrared light pulsed through
10 ft-long, I/O f*-dtaa fiber optics, ora end at blob
pntentfal and tbe other end at ground potential.
Coneerston Is accomplished by digitizing analog signals
befbre transwittlog through tie optical system and de*
modulating at tbe terminating end. A maximum tanver-
sten rate of 100 iHt provides adequate resolution to
operate the ion source. the output data is documented
and stared In a fUMI computer. Although tbe control
iaput is computer compatible, no atterpt has been made
fur closed loop feedback control of tbe Ion source.
Introduction
Over the years of high voltage accelerator opera-
tions of «a«y research laboratories, tbe problem of
control tiny and monitorta? equipment that operates at
eteuated volcaye bas been attacked In many ways, most
Have been adequate but not necessarily ideal. Control
of various functions bas teen rede with insulated rods
and servos, strtnys and tmlltys, pneumatics, and other
tnyeneous devices. Making measurements or reading
meters across the high voltage gradient is a bit more
difficult. It bas been done with binoculars, closed
circuit television, and with operators with good eye*
styht. Radio frequency telemetry was an earlier
approach which In many cases was quite successful but
was limited in the number of channels unless a Urge
array of complicated equipment was used; the electrical
nrntse generated by high voltage machines also contri-
buted to the problem ton letcTriai small signals due
to Interference. Uith tbe advancement of solid state
devices, new components war* developed (light emitting
diodes, phototransistors, ohotosilicon controlled
rectifiers, Itskt activated snitches, and ether stellar
devices} to construct control systems that woutd
bridge the high voltage yap. Insutated, low leakaoe
fiber optic cables were perfected with good light
transmission characteristics, numerous enatog-to-
digital and dlyital-to-analog converters also became
ever able. &o»lino these various comsonents together.
• simple, low cost telemetrv system was constructed
and put teto operation.
frtnctmle of Operation
Several methods could be employed to transfer
analog data across a high voltage gap as long as it
was digitized oefore being transmitted. The data
could fe sisdlexed or multiplexed depending on tbe
writer of channels required and tbe resolution that
meuld be adequate far meaningful Information, Nuuer*
uus iingle channels sera chosen became they provided
good resoluifs# and hades** flexibility than multi*
plumed channels. Tbe type of conversion that is used
It analog voltage-to-frequency and frequeccy-io-analog
voltage in both the up-lint and the down-1 ink control
cbaravls; it uses a maximum conversion rate of 108 idle
with twists of d-»see wide, figure I illustrates tbe
basic diagram of each up-Iln* control A
3-10-V dc reference voltage applied to the input of
tfeseart* sponsored by the Department of Energy under
contract wvtb Union Carbil* Giraoratfon,
anplifier and light emitting diode coupled to a 1/8-tn,
I0*ft*long fiber optic bundle which serves as the
insulating sodium. Tbe Infrared light pulses are
transmitted through the optics to a phototransistor at
the high potential end. The amplified pulses are
converted tack to analog control signals by the re*
verse process.
Figure 2 illustrates a down-link monitor channel
for reading various voltages end currents from equip-
ment that operates at a high potential. A 0-250-mv
analog signal from any sensing element is amplified to
0*10 ¥ dc. Hie 0*10 V dc is digitized to 0*100 kHz
and transmitted to ground potential throw* tbe fiber
outics. Tbe anollfted twists are converted back to the
original analoo tlenal that was sensed at blob volt toe.
Tbe analog signal at ground potential now can be further
processed or directly read with a meter or oscilloscope-
Optical Interface
fhoto 1 shows the front view of a 20-channel,
corona free optical interface; 7 channels are wp-l!nk
controls and 13 are down-link monitors. Tbe ends of
the 10-ft-long fiber optical cable are terminated with
standard BhC coaxial cable connectors that have bad
a portion of the Teflon insulator punched out.
Photo 2 shows the rear view of the interface and
two conductor Rg-108/U iwinax cable connecting the
phototramsis tors and light emitting diodes to tbe
control console. The optical devices are connected
to the rear of tbe twtnax chassis connectors and pro-
trude through hoi low 8KC connectors on tbe front side,
where tbe optical coup] ing is made. In event of e
failure, any photo device can be replaced without
disassembling the unit. The Interface unit can operate
up to 200-kV corona free with little or no leakage.
Control end Monitor Reautrewents
The 20-channel system was developed to operate a
duoFKatron ion source for neutral beam Injectors,
as shown In fbotos 3 and d. The significant control
and monitor parameters of the ion source system that
operates at accelerating potential are transmitted to
ground by telemetry. The filament, Magnet, and auxiliary
magnet power supplies require one control line and one
monitor line each. The control line drives a saturable
core reactor which controls the power supply output
currant; the monitor line measures the dc current at
the operator's console. The 220-v dc, 1S0C-A arc
power supply requires three optical links, one pulse
line and two monitor lines. The pulse line switches
the one-half wave delta-wye switching silicon controlled
rectifiers in the secondary of the power supply on and
off. The current and voltage at high potential are
transmitted to ground potential with two monitor
lines. The power supply is controlled by an auto-
transformer at grouiti potential and does not require
telemetry lines. The ion source hydrogen gas system
uses two piezoelectric valves to control the flow
end pulsed nas into the ion source; two control lines
perform both the pulsing and level of gas flow.
Pressure fn the ion source is read from a thermocouple
pressure indicator and transmitted to oround bv the
telemetry. In addition, anv other ion source parameter
can be. monitored and displayed at the operatino console
with an appropriate sensing decent that has a'O-jSO-m*
output.
OtSTIitt8UT10N Of THIS CCi;uv.L\’7 5S J.NUMITEDl
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Wright, R.E. Optical telemetry control and data transfer system, article, January 1, 1977; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1072309/m1/1/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.