(a) When the RESET button is pushed.
(b) When the POWER switch is placed to ON, lamp test will light for
about 2 seconds.
(c) When switching between detent positions of the GATE TIME switch,
FUNCTION switch, or DISPLAY POSITION switch.
(d) When the counter is attempting
to
phase
lock
the
internal
oscillator to an external standard.
(e) When the counter has gone into excessive gate time.
2.
OPERATION
a. Input Triggering.
The input circuits provide triggering over a
range of -1.3 V to + 1.3V.
The point at which triggering occurs is
adjustable with the front panel LEVEL control.
Each input channel has a
small amount of hysteresis (about 10 mV).
If the SLOPE switch is set to
"+", the trigger pulse occurs at the top of the hysteresis window. If the
SLOPE switch is set to "-", the pulse occurs on the bottom line of the
window. In other words, the signal must pass through the entire hysteresis
window before a trigger pulse is generated (see figure 3).
The LEVEL
control must be placed to allow at least a 1 ns pulse width for the Schmitt
Trigger.
b. Excessive Gate Time.
In every measurement involving a gate time,
the counter depends on the input signal to terminate the measurement. The
measurement concludes one clock pulse after the next input pulse following
the end of the gate time, not with the gate time itself. If the period of
the input signal is much longer than the gate time or if the signal is
interrupted sometime during the gate time, the excessive gate time circuits
prevent the counter from waiting indefinitely for the terminating pulse.
The counter will wait for about 3.5 times the selected gate time before
resetting. At the end of the excessive gate time, the display will flash
instantaneously to lamp test before displaying all zeros.
c. Measurement Technique. The counter uses a period average technique
to make measurements.
The counts (or pulses) that are generated from the
input and time base signals are collected in separate scalers (dividers)
during the measurement time.
The counter compares these pulses
arithmetically and displays the result on the front panel.
d. Operating Modes.
The following paragraphs describe the operating
modes
for
period,
time
interval,
ratio,
and
totalize
measurements.
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