3 1/2 CAP AUTO DMM
1.7 Frequency counter
The time base of the frequency counter is derived from an external crystal oscillator by
T
counter
=
4000000
F
osc
ES51982
where f
osc
is the frequency of the crystal oscillator. Thus, the counter has a 1 second time
base when a 4MHz oscillator is used. The frequency counter can select the proper range
automatically or manually. Auto-range operation extends over five decades, from 2KHz
to 20MHz The following table summarizes the full scale range of the frequency counter.
Range
FR1
FR2
FR3
FR4
FR5
Full Scale
2.000KHz
20.00KHz
200.0KHz
2.000MHz
20.00MHz
1.8 Auto power off
ES51982 has a default auto power off function. If the meter idles for more than 10
minutes, the chip automatically turns the power off. When this happens, the state of the
meter is saved. In order to disable auto power off function, power on the meter when
any of the push function, except for HOLD, is pressed down. In addition, when RS232
output is active, the auto power-off function is also disabled. The APO sign on the LCD
panel indicates whether the auto power-off is enabled or not.
Note:
Powering on the meter while pressing HOLD turns on all LCD segment until
HOLD is pressed again.
1.9 Sleep
The meter enters sleep mode after auto power off. The SLEEP pin asserts low (-3V) in
the sleep mode, and asserts high (+3V, not 0V) after re-power on.
1.10 Re-power on
After auto power-off, pushing any of the push function or changing the rotary mode can
turn on the meter again. If the meter is re-powered on by changing the rotary mode, the
saved state is cleared. If the meter is re-powered on by push functions, the chip restores
the saved state and enters HOLD mode. The LCD displays the saved value.
9
11/01/05
CYRUSTEK [ Cyrustek corporation ]
