08/09/09

9

ES51982

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

4000000

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

Full Scale

FR1

2.000KHz

FR2

20.00KHz

FR3

200.0KHz

FR4

2.000MHz

FR5

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.