ES51931
22,000 Counts Auto DMM
1.8 Frequency counter
The time base of the frequency counter is derived from an external crystal oscillator by
4,000,000
Tcounter
=
Fosc
where Fosc is the frequency of the crystal oscillator. Thus, the counter has a 1-second
time base when a 4MHz oscillator is used. The frequency counter can select the proper
range automatically or manually. Auto-range operation extends over seven decades,
from 22.00Hz to 220.00MHz. The following table summarizes the full-scale range of
the frequency counter. In frequency mode, press VAHz button switches the mode
to/from duty cycle mode.
Range
2FR1
3FR2
FR3
FR4
FR5
Full Scale
22.00Hz1
220.0Hz1
22.000KHz
220.00KHz
2.2000MHz
22.000MHz
220.00MHz
FR6
FR7
NOTE:
1In the range FR1~FR2, the maximum counting number is 2200 counts.
2In the Range FR1, ES51931 will show 0.00Hz if the input frequency is less than 2.00Hz.
3In the Range FR2 (manual mode), ES51931 will show 0.0Hz if the input frequency is less than 20.0Hz..
1.8.1 Duty Cycle measurement
The duty cycle measurement is available in frequency mode with VAHz operation. Press
VAHZ key when frequency mode is in operation, the ES51931 will switch to duty cycle
measurement mode. Press VAHz key again to switch to frequency measurement mode
also. The duty cycle mode range is within 5.0% to 94.9%. The minimum resolution is
0.1%. If the source frequency duty cycle is smaller than 5.0%, the UL will be shown on
the LCD display. If the duty cycle is larger than 94.9%, the OL will be shown on the
LCD display.
Ver. 1.2
11
10/05/27
CYRUSTEK [ Cyrustek corporation ]
