Signametrics
38
C to
his is particularly important for signals with low duty-cycle and small amplitude relative to the
a
shol
ails.
set range will guarantee the signal is within the
li
on of the AC circuitry and gives the best performance.
he totalizer can be selected while the DMM is in the ACV mode. It is capable of counting events such as over-
voltage excursions, switch closures, decaying resonance count, etc. The active edge polarity can be set for a positive
or negative transition. A count of up to 10
9
can be accumulated. The maximum rate of accumulation is 30,000
events per second.
The Threshold DAC can be set for a negative or positive voltage value. See Threshold DAC above for more details.
Example One: To monitor and capture the AC line for positive spikes which exceed 10% of the nominal 120 V
RMS value, first select ACV 250 V range, than set the Threshold DAC to 186.7 V. This value is the peak value of
120 V RMS plus 10% (120V + 10%) X
4.12.3 Duty Cycle Measurement
Duty Cycle of signals from 1 Hz to 100 kHz can be measured. The minimum positive or negative pulse width of
the signal must be at least greater than 2
µ
s. When measuring duty cycle precisely, the voltage at which the
measurement is made is important, due to finite slew rates of the signal. The Threshold voltage can be set for
precise control of the level at which duty cycle is measured
.
For best measurement results, set the Threshold DA
the Median value. T
selected scale.
4.12.4 Pulse Width
User selectable positive or negative pulse widths may be measured for signal frequencies of 1 Hz to 100 kHz and
minimum pulse widths of 2
µ
s. The Thre
d DAC feature allows measurements at a pre-defined signal level. See
Threshold DAC above for more det
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
near regi
4.12.5 Totalizer Event Counter
T
2
). Enable the Totalizer and read it periodically to get the number of
times this value was exceeded.
Example Two: Defects in coils, inductors, or transformers can be manifested as an increased decay, or greatly
attenuated resonance when stimulated with a charged capacitor. The Totalizer function can be utilized to count
transitions above a preset Threshold voltage as in the figure below.
Figure 4-13. Measuring inductor Q by counting transitions of decaying resonance with preset threshold.
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