Ludlum Measurements 177, Руководство пользователя

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Model 177
Technical Manual
Section 8
Ludlum Measurements, Inc. Page 8-3 October 2018
For counting, audio pulse width is set by R113/C111 of U011 with one
pulse per count. For an alarm condition, Pin 4 U111 is held high through
CR112 until alarm is reset. Alarm audio tone is controlled by R117 and
C112.
High Voltage (HV)
The high-voltage power supply is a blocking oscillator utilizing Q401-T411
and quadrupler CR123, CR421, CR422, and through CR423. The HV
output is controlled by conduction to ground through Q302. With Q302
saturated, the HV output is maximum.
The op amp, U311 Pins 1, 2, 3, is used as a comparator to compare the
voltage reference at Pin 3 to the feedback voltage at Pin 2 through R322 for
voltage control and regulation. High voltage is adjusted by
HV
control R311
changing bias on Pin 2 U311. With the HV control wiper at ground, high-
voltage output is maximum.
Low Voltage
Low voltage is supplied by internal battery B1 (wiring diagram, 347 × 126)
or external power T1. Unregulated power at C125 is coupled to voltage
regulator VR211 and battery charger U201-Q301.
Regulated low voltage is supplied to the balance of the circuit through
VR131 at 5.0 volts and U301 at 1.2 volts.
Battery Charge
Battery charge is provided by voltage regulator U201 and power transistor
Q301. R402 limits charge current for discharged battery. A negative voltage
coefficient of -0.0063 volts per degree F is provided by ratio of R013/R201.
R013 sets output voltage to 6.825 volts.
High Voltage Test
High voltage test is supplied by R001 through
HV TEST
switch,
BAT TEST
switch,
ALARM TEST
, Pin 5 of U311, and then the meter. The HV readout is
calibrated by R001.
Alarm Set Voltage
Alarm set voltage is coupled from
ALARM SET
control through the
ALARM
TEST
switch, voltage follower Pin 5 of U311, and to the meter.