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Model DMM uses an interactive counting technique to measure frequency and period. This method
generates constant measurement resolution for any input frequency. All frequency counters are subject to
errors when measuring low-voltage, low-frequency signals. Both internal noise and external noise are also
critical when measuring low-voltage, low frequency signals. Measurement errors will also occur if you
attempt to measure the frequency (or period) of an input following a dc offset voltage change. You must
allow the multimeter's DC input blocking capacitor to fully settle before making frequency measurements.
3.5.2
Gate Time
Gate time is the amount of time Model DMM uses to sample frequency or period readings. All settings of the
RATE function (Fast, Med and Slow) yield a gate time of one second.
3.5.3
Connections
Assuming Model DMM is under factory default conditions, the basic procedure is as follows:
1. Connect test leads to INPUT HI and LO terminals.
2. Select frequency or period measurement functions by pressing Freq or Shift → Freq
3. Connect test leads to the source as shown in Figure 3-4:
CAUTION:
Do not exceed 1000V peak between INPUT HI and INPUT LO or instrument damage may
occur.
4. Taking a reading from the display
Input Impedance =1MΩ in parallel with <100pF
CAUTION:
Maximum Input = 750 RMS, or 1000V Peak
Figure 3-4
Frequency and Period Measurements
ABM-4082
25
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