Measuring Waveforms
3–102 TDS 684A, TDS 744A, & TDS 784A User Manual
To measure the amplitude of a waveform, do the following steps:
1. Press the channel selection button of the channel you wish to measure. Note
the vertical scale factor for the channel in the channel readout on screen.
2. Count the graticule divisions between two features to be measured and
multiply by the vertical scale factor.
For example, if you count five major vertical graticule divisions between the
minimum and maximum values of a waveform at a scale factor of 100 mV/di-
vision, then you can easily calculate your peak-to-peak voltage as:
5 divisions ×100 mV/division = 500 mV.
NOTE. When you select the NTSC graticule, the volts per division of all selected
channels is set to 143 mV/div (152 mV/div for PAL) where the divisions are those
of the conventional graticule, not the divisions of the video graticules. For
NTSC, the actual grid lines represent 10 IRE, and for PAL the lines are 100 mV
apart.
To measure the time of a waveform, repeat the process just described, but count
the horizontal divisions and multiply by the horizontal scale factor. For example,
if you count five major vertical graticule divisions for one waveform cycle at a
horizontal scale factor of 50 S/division, then you can easily calculate the
waveform period as:
5 divisions ×50 S/division = 250 s, or 4 kHz.
Optimizing Measurement Accuracy: SPC and Probe CalThe TDS Oscilloscope provides two features that optimize measurement
accuracy. Signal Path Compensation (SPC) lets you compensate the internal
signal path used to acquire the waveforms you acquire and measure based on the
ambient temperature. Probe Cal lets you compensate the entire signal path, from
probe tip to digitized signal, to improve the gain and offset accuracy of the
probe. This section tells you how to use both features.
The TDS Oscilloscope lets you compensate the internal signal path used to
acquire the waveforms you measure. SPC optimizes the oscilloscope capability
to make accurate measurements based on the ambient temperature.