Operator`s manual
Signametrics 48
In Figure 4-13, the DMM is set to 2.4 ACV range, while the input is a 10% duty-cycle wave with 5 V peak-to-
peak. Due to AC coupling, the input at the comparator is –0.5 V to + 4.5 V. The Median Value is +2.0 V,
which would be the optimal Threshold value.
Figure 4-14. Comparator and Threshold DAC Settings
4.14.2 Frequency and Period Measurements
Freq. measures from 2 Hz to 300 kHz. When activated, the
. The reading rate is
(Per) is also selectable.
cond.
matic.
xt frequency measurement is made at the last selected range.
y cycle precisely, the voltage at which the measurement is made is
im ortant, due to finite slew rates of the signal. With the SM2064, the Threshold voltage can be set for precise
sults, set the Threshold DAC to the
Med nd small amplitude relative to the
sele
r-
ositive
Both Freq. and Per. check boxes are only visible when ACV or ACI functions are selected. These check boxes are
used to make frequency or period measurements.
control panel alternately updates the amplitude reading followed by the frequency reading
slower than indicated when frequency is activated. In the Windows control panel, period
Once the frequency range is acquired, Frequency and Period have a maximum measurement time of about 1 se
It could take up to five measurements before the correct frequency range is auto-selected. This process is auto
Once within range, the ne
Both Frequency and Period measurement performance can be improved by properly setting the Threshold DAC, a
novel feature of the SM2064. See “Threshold DAC”, “AC Median Value”, and “Peak-to-Peak” measurements for
further details.
4.14.3 Duty Cycle Measurement
Duty Cycle of signals from 2 Hz to 100 kHz can be measured. The minimum positive or negative pulse width of the
signal must be at least 19µs. When measuring dut
p
control of the level at which duty cycle is measured. For best measurement re
ian value. This is particularly important for signals with low duty-cycle a
cted scale.
4.14.4 Pulse Width
User selectable positive or negative pulse widths may be measured for signal frequencies of 2 Hz to 25 kHz and
minimum pulse widths of 19 µs. The Threshold DAC feature allows measurements at a pre-defined signal level.
See Threshold DAC above for more details.
To measure pulse width, the DMM must be in the AC volts range appropriate for the input voltage. Keeping the
peak-to-peak amplitude of the measured signal below 5.75 times the set range will guarantee the signal is within the
linear region of the AC circuitry and gives the best performance.
4.14.5 Totalizer Event Counter
The Totalizer can be selected while the DMM is in the ACV mode. It is capable of counting events such as ove
voltage excursions, switch closures, decaying resonance count, etc. The active edge polarity can be set for a p
or negative transition. A count of up to 10
9
may be accumulated. The maximum rate of accumulation is 30,000
events per second.