Ver. 3.2

10/06/23

7

ES51921

22,000 Counts Auto DMM

1.1.2 CE selection

ES51921 has a CE selection feature archived by configuring a CESEL pin. If pin CESEL is connected to

V-, ES51921 will have a 610.0V overflow level in DCV and ACV ranges. If pin CESEL is connected to

DGND, the overflow level will be set to 1010V. When it is floating, the overflow level is set to 1500V in

DCV mode and 1010V in ACV mode. The meter will show OL when the measuring signal reaches the

overflow level. The configuration of CESEL is listed below.

CESEL

DCV

ACV

V-

610.0

610.0V

DGND

1010.0V

1010.0V

Floating

1500.0V

1010.0V

1.1.3 HCF signal detection

ES51921 provides detection of high-crest-factor (HCF) signal in ACV mode. When this

function is enabled, ES51921 senses the signal and determines it as HCF if the Vpp is

large enough. Once the signal is determined as HCF, ES51921 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 Vpeak=240V, Vrms=40V(CF=6) was applied, traditional DMMs

might stay at 22.000V 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 220.00V and exhibits more accurate results.

In addition to accuracy improvement, HCF will speed up the measuring process for

high voltage signals. For example, a 500Vrms is applied, ES51921 will take about

180ms (3 HCF jumps) to enter 1000.0 V range. And it takes 1 or 2 measuring processes

to obtain the stable result. Thus a stable LCD reading could be obtained within 1 sec.