v1.2

11/09/06

7

1.1.3 HCF signal detection

ES51916 provides detection of high-crest-factor (HCF) signal in ACV mode. When this

function is enabled, ES51916 senses the signal and determines it as HCF if the Vpp is

large enough. Once the signal is determined as HCF, ES51916 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=500V, Vrms=100V(CF=5) was applied, traditional 4000 counts

DMMs might stay at 400V 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 4000V and exhibits more accurate results.

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

high voltage signals. For example, a 1000Vrms is applied, ES51916 will take about

180ms (3 HCF jumps) to enter 1100.0 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.

In determining whether the input signal is HCF, ES51916 senses the signal at VR1 for

fast response. However if a signal consists of a small ac part and a large enough dc part,

ES51916 might incorrectly treat it as HCF. This could incur range looping phenomenon,

i.e., the measurement could not settle to a specific range.