V 1.2

13

2016/04/27

ES251

2000 Counts DMM

1.9.

Frequency Counter

The time base of the frequency counter is derived from an external crystal oscillator by

4,000,000

when a 4MHz oscillator is used. The frequency counter can select the proper range automatically or

manually. Auto-range operation extends over six decades, from 200.0Hz to 20.00MHz. The following

table summarizes the Full-Scale range of the frequency counter.

Range

Full Scale

FR1

200.0Hz

FR2

2.000KHz

FR3

20.00KHz

FR4

200.0KHz

FR5

2.000MHz

FR6

20.00MHz

*If input frequency is less than 1.0Hz, ES251 will show 0.0Hz

1.10. Electrical field detection mode

ES251 supports a non-contact AC voltage measurement, which is called electric field measurement

also. The ADC input is configured from ADP pin vs. SGND. When no or less electric field is detected,

the LCD display shows “EF”. If the electric field is detected, the strength will be showed on the LCD

display by “-“ not digits type. Level 1(equivalent to 12.5% full scale of ADC) is “-“ and the level

4(equivalent to 100% full scale of ADC) is “----“. Additional beeper (BUZOUT pin) and LED alarm

(ALARM pin) will be active from ES251. The frequency of buzzer and LED alarm depends on the

strength of electric field also. The faster beeper means the stronger electric field (AC voltage) is

sensed.

Mode

FC1~4

SLACDC

Input Terminal

EF

1,1,1,0

1

ADP V.S. SGND

ADP

100M

EF test circuit

EFin+

SGND

AGND

EFin-

100k

VRADP

-400mV