Model 2360
Technical Manual
Section 8
Ludlum Measurements, Inc.
Page 8-2
July 2016
Beta pulses from pin 1 of U011 are coupled to univibrator U101. Pulses are
coupled to the µP from pin 7 of U101 as long as pins 3 and 13 of U011
remain high (+5 V). When an alpha and/or a beta window pulse is present,
the reset (pins 3 and 13 of U101) function is enabled, and 7 of U101 remains
high. Pin 7 of U101 is connected to pin 13 of U101 to provide a time delay
for the µP clock cycle to complete before the next beta pulse can be
recognized by the µP.
Low Voltage Supply
Battery voltage is coupled to switching regulator U201 and associated
components to p5 V to power op-amps and logic circuitry. The
charge pump (cp) output C202, CR211, CR212, and C201 form a voltage
doubler circuit to p9 V for U201 amplifier supply. U001 and related
components p2.5 V reference for
HV SET
and alpha/beta
discriminator controls. R201 (
LO BAT
) is adjusted so that the meter pointer is
aligned with the left vertical mark on the
BAT OK
line with 2.2 V battery
input.
High Voltage Supply
High voltage is developed by blocking oscillator Q421, T321, C412, and
rectified by voltage multiplier CR221-CR224, C221-C223, C211, and C114.
High voltage increases as current through Q421 increases, with maximum
output voltage with Q421 saturated.
High voltage is coupled back through R123 to op-amp pin 2 of U311.
Resistor network R211-214 completes the
HV
division circuit to ground.
R214 provides
HV
limit at 2.0 kV when the
HV
SET
control on the calibration
board is at maximum. The regulated
HV
output is controlled by
HV
potentiometer located under the
CAL
cover on the front panel. This control
provides the reference for comparator pin 3, U311. During stable operation,
the voltage at pin 2 of U311 will equal the voltage at pin 3 of U311. Pin 1 of
U311 will cause conduction of Q312 to increase or decrease until the
HV
finds a level of stability. R115 (
HV
TEST
) calibrates the analog meter to the
HV
output when the
HV
test push-button switch is depressed.
Detector Overload
A voltage drop is developed across R121 and sensed by comparator U012 as
detector current increases. When the voltage at pin 3 of U012 goes below
pin 2, pin 1 goes low, illuminating the
OL LED
and driving the meter to full
scale. R211, overload, provides adjustment for the overload set point.
Summary of Contents for 2360
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