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2.3.3.
Frequency Measurement
When a precise determination of frequency is needed, a frequency counter is obviously the first choice. A
counter can be connected to the CH 1 OUTPUT connector (30) for convenience when both scope and
counter are used. However, and oscilloscope alone can be used to measure frequency when a counter is
not available, or modulation and/or noise makes a counter unusable.
Frequency is the reciprocal of period. Period in seconds (s) yields frequency in Hertz (Hz); period in
millisecond (ms) yields frequency in kilohertz (kHz); period in microseconds (µs) yields frequency in
megahertz (MHz). The accuracy of his technique is limited by the timebase calibration accuracy (see
Table of Specifications.)
(a) 10 ms Division
2.3.4
Phase Difference Measurements
Phase difference or phase angle between two signals can be measured using the dual-trace feature of
the oscillocope, or by operating the oscilloscope in the X-Y mode.
Dual-trace Method
This method works with any type of waveform. In fact, it will often work even if different waveforms are
being compared. This method is effective in measuring large or small differences in phase, at any
frequency up to 20 MHz.
To measure phase difference by the dual-trace method, proceed as follows:
1.
Set up the scope as described in 2.3.3 Dual-trace Operation, connecting one signal to the CH 1
IN connector (24) and the other to the CH 2 IN connector (22).
Note:
At high frequencies use identical and correctly-compensated probes, or equal lengths of the
same type of coaxial cable to ensure equal delay times.
2.
Position the Trigger Source Switch (18) to the channel with the cleanest and most stable trace.
Temporarily move the other channel's trace off the screen by means of it Vertical POSITION
control.
3.
Center the stable (trigger source) trace with its Vertical POSITION control, and adjust its
amplitude to exactly 6 vertical divisions by means of its VOLTS/DIV switch and VARIABLE
control.
4.
Use the Trigger LEVEL control (9) to ensure that the trace crosses the central horizontal gratitude
line at or near the beginning of the sweep. See Figure 2-10.
Figure 2-7: Time Interval Measurement
- 48 -
(b) 2 ms Division
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