Ver 2.7

7

07/10/03

ES51927

6000 Counts Smart DMM

1.1.2 HCF detection

ES51927 provides detection of high-crest-factor (HCF) signal in ACV auto range

mode. ES51927 senses the signal and determines it as HCF if the Vpp is large

enough. Once the signal is determined as HCF, ES51927 will jump up one

measuring range regardless of current measurement value. It takes 60ms to jump

one range up. The jumping up process will continue until the maximum range is

reached. With HCF detection, a more accurate result could be obtained. For

example, when a input signal with Vpp=350V, Vrms=70V(CF=5) was applied,

traditional DMM might stay at 60V range but shows counts with the amount of

error up to 10% or even bigger. The error rises from limited input/output swing

at internal ADC. With HCF detection, DMM will stay at 600V range and

exhibits more accurate results.

1.1.3 EF mode

ES51927 supports a non-contact ac voltage measurement, which is called electric

field measurement also. The EF mode is selected by SEL key when EF_EN is

active. The ADC input is configured from ADP pin vs. SGND. When no or less

electric field is detected, the LCD shows “EF”. If the detector senses electric

field, the strength will be showed on LCD by “-“ not digits type. Level 1(weak)

is “-“ and the level 4(strong) is “----“. Additional beeper will be output from

BUZOUT pin. The buzzer frequency depends on the strength of electric field also.

The Faster beeper means the stronger electric field (ac voltage) is sensed.