Tektronix 710 Instruction Manual
INSTRUCTION MANUAL
MODEL 710, 711
MILLIVOLT DISCRIMINATOR
MODEL 710/7ll COltTEnTs
TABLE OF coNTm
SECTION
INT~WCTION . . ..*.........*.....*.*......*....*....
SPECIFICATIONS
DESCRIFTIO~
. . . . . . . . . . . . . . . . . . . . . . . . . . ..~......#. II
,.....,...........*..,..,*.*.,.....,.... III
OPERATION . . . . . . . . . . . . . . ..*.....................*...
MAINTENANCE
.,....,..*....,...,......*....,,........
Voltage Chart
Schematic D1aSr.m
Replaceable Parts List
I
IV
V
i
MODEL 710/711
SECTION I - IN'J!ROIlJCTION
A. Models 710 and 7ll MilUvolt Discriminators
These Millivolt Discriminatorn are extremely stable, light-
modulator clc amplifiers operating a thyratron tube end reley.
They are identical except for the method of the trip level
adjustmenta.
Trip level of the 710 and 7l.l is variable from 0.2 to 10 milli-
volts.
resistive divider, or to lo-
justment of the 710 is made with an external reference aad po-
tentiometer located behind the front panel. The 711 is adjusted
by means of a calibrated dial in the front panel.
is accurate within 2200 uv .
The instnuncnts may be made either locking or non-locking.
They are chatter-free on non-locking and locking operation;
modification for locking action is easily made by adding a nor-
mally open switch.
The range may be extended to 1000 volts with au internal
ampere with a current shunt.
INTROLWCTION
Ad-
Dial setting
Long term repeatability of the 710 and 711 is better than 200
micmvoltn, and the speed of response is between k~ end 60
milliseconds with a signal 5% larger than the trip level.
Standard units are wired to trip for signals exceeding the trip
point and are fail-safe in that failure of any component cause6
the alarm condition.
decreases below the trip point, the unit is not fail-safe if
a loss of reference signal occurs.
Careful shielding, filtering, and guarding permit floating oper-
atlon up to 500 volts above ground, with excellent rejection
to extraneous voltages.
from each other and from ground.
Inmmnity to vibration and indefinite life under rigorous envimnmental conditions are assured by the use of premium subminiature
tubes and a Keithley designed photo-reeistive modulator having
no mating parts.
tines.
On units wired to trip for a signal that
Input and output terminals are isolated
Permissable overload is greater than 10,000
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MODEL 7LO/711
SPECIFICATIONS
SECTION II -
SPECIFICATIONS
Models 710 and 711 are identical except for the means of adjust-
ing the trip level.
TRIP LrnL: Model 710: Adjustment made with an external refer-
ence and potentiometer located behind front panel.
Model 7l.l:
on the front panel.
Adjustment made with a calibrated dial
Dial setting of trip level
is
accurate within +2CO uV.
SENSITIVITY:
0.2 to 10 millivolts.
Range can be extended to
1000 volts with an internal reoistive divider.
MAxIMuM SOURCE IMPEDANCE: 100 K
INPUT IMPEDANCE: From Lo to GROUND or INPUT to OUTPUT, over
1000 megohms shunted by .0047 mfd.
than lmegobm.
Maximum voltage above ground, 500 volts, dc or
Across input terminals, greater
peak.
OUTPUT:
REPEATABILITY OF TRIP FOINT:
Relay contacts, DPDI!, 5 amps, IlO v, noninductive.
Better than 200 microvolts.
STABILITY OF TRIP FOINT:
+-0.3% with +lO$ line change.
60 CR3 REJECTION: 100 millivolts of 60 cps on dc signal will
cause less than 1% shift of trip point;
RESPONSE SPEED: As shown in Figure 1, speed depends somewhat
on the degree to which the trip point is exceeded. Reclosure
time ia approximately 30 milliseconds.
TRIP POLARITY:
PERMISSIBLE 0VERu)A.D:
TRIP RESET:
Positive or negative
Greater than 10,000 times.
Automatic when the standard non-locking mode of
operation is used; differential between trip and reset is less
than 200 uv.
When modified for locking action, a reset switch
is added.
TRIP INDICATION:
VOLTAGE REFERENCE:
Red light on front panel.
One RM&XlR mercury battery. Battery life
is in excess of 10,000 hours.
'RJBE, TPANSISMR COMPLEMENT:
1-6940; l-6788; 1-5643; l-m398
MODULA~RS:
KWER:
2 Keithley Model 1510 Modulatora
x1.7 v, 60 cpe, I2 w; 230 v models on order
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dPECIFICA~ONS
ACCESSORIES SUPPLIED: MatIn@; connectors; input, outputi
ACCESSORIES AVAILABLE: Model 7105 Case: Model 7102 Rack Freme
for mounting up to 7 UnIta.
DlldENSIONS: 8" high x 2#" wide x 13$’ deep.
MODEL 710/7ll
2-2
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MODEL 710/7ll
SECTION III - DESCRIPTION
The Model 710 and 711 Millivolt Discriminators consist of a three
stage vacuum amplifier following a modulator and an input filter.
The output of the amplifier is synchronously demodulated and filtered
to provide a D.C.
controls a relay.
The input contains the D.C. to A.C. modulator, an input filter to
reject spurious AX. signals and the Trip Level reference set.
The modulator used in the Millivolt Discriminator employs two photo-
conductive cells, PD-101 and PD-102, which operate from the transfarmer secondary. This action is similar to a single-pole doublethrow mechanical chopper with the result that the D.C. input and
the D.C. reference are converted to an A.C. signal. With no signal
at the input of the amplifier either from the reference or the input,
the negative bias cuts off the thyratron and the relay drops out.
When a reference signal is fed to the amplifier, the negative bias
at the grid of the thyratron is cancelled and the thyratron fires
and energizes the relay.
that is with the relay energized. Operating in this manner the Model
710 and "(11 will indicate an alarm condition in the event of any
tube failure in the unit or from the loss of this reference signal
by any other means.
bias on the thyratron. If bias is lost, the transistor opens the
cathode circuit of V3 and gives the alarm condition. The modulator
compares the input signalto the signal set by the Trip Level. If
the input signal is less than the level set by the Trip Level pot.,
the D.C. voltage to the thyratron grid keeps the thyratron on. If
the input signal exceeds the reference signal the tbyratron extinguishes
and indicates the alarm condition by means of a red light on the
front panel.
signal at the grid of a thyratron.
This ie the normal condition of operation,
The transistor, Cl protects against loss of
DESCRIPTION
The thyratron
Spurious AX. signals are prevented from entering the input by means
of a "twin-tee" filter consisting of R-102 through R-106 and C-101
through C-103 which is tuned to line frequency. X-104 and R-106
are set at the factory for maximum rejection to line frequency.
The demodulator circuit employs a four-diode bridge with silicon
diodes.
of the transformer secondary is not necessary.
driven synchronously with the neon lamps which switch the input modulator .
is filtered and fed to the grid of the thyratron.
The basic sensitivity of the instrument is 10 millivolts, however,
reduced sensitivity may be obtained by the use of a divider.
The output is obtained as a D.P.D.T. set of contacts from a relay
which is used for control.
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A balanced configuration is used so that careful balance
The demodulator is
The demodulator output is a pulsating DC. signal which
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