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

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

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

may be accumulated. The maximum rate of accumulation is 30,000

events per second.