ES51969
6,600 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 six decades, from
660.0Hz to 66.00MHz. The following table summarizes the full-scale range of the
frequency counter.
Range
FR1*
FR2
FR3
FR4
Full Scale
660.0Hz
6.600KHz
66.00KHz
660.0KHz
6.600MHz
66.00MHz
FR5
FR6
*If input frequency is less than 10.0Hz, ES51969 will show 00.0Hz.
1.9 Duty cycle measurement
In frequency mode, press the VAHZ bottom will force ES51969 enter duty cycle
measurement mode. The duty cycle measurement mode takes high input from FREQ
pin, and low input from SGND pin. The annunciator “%” on LCD panel indicates
whether the duty cycle measurement mode is activated. When the duty cycle is less
than 10.0%, the LCD panel shows UL and the UL bit of RS232 data becomes high.
When the duty cycle is more than 94.9%, the LCD panel shows OL and the OL bit of
RS232 data becomes high. If the frequency of input signal is less than 10.0Hz, the LCD
panel also shows UL and the UL bit of RS232 data becomes high. ES51969 also
provides a single duty cycle mode, which FC1~FC4 = {1,1,1,0}, as an independent
rotary switch for the meters without a frequency mode configured.
1.10 Temperature measurement mode
Temperature measurement mode takes input signal from ADP pin and reference voltage
from (VA+ - VA-). ES51969 has a built-in ºC-to-ºF scale translation circuit, and only
needs an external ºC scale application circuit. The application circuit for ºF scale is not
required. In temperature measurement mode, the default range is 6600 ºC or ºF. The
VBAR pin is used to control the first decimal point (DP1) on the LCD panel. When
VBAR is pulled to V-, DP1 will be turned on and the full scale becomes 660.0 ºC or ºF.
v2.6
12
08/10/06
CYRUSTEK [ Cyrustek corporation ]
