1-3
1
IM 701830-01E
Functions
1.2 Setting the Vertical and Horizontal Axes
Sample rate
Changing the time axis causes a corresponding change in the sampling rate. Maximum sampling rate is
10MS. The waveform can only be displayed correctly at frequencies up to half the sample rate, due to
Nyquist’s theorem*. Sample rate is expressed in S/s (number of samples per second).
* If the sample rate is higher than the frequency of the input signal, high frequency components will be
lost. In this case, a phenomenon in which high frequency components change to lower frequency
components occurs, due to Nyquist’s theorem. This phenomenon is called aliasing. Aliasing can be
avoided by setting the acquisition mode to envelope mode and acquiring the waveform.
Aliasing signal
Input signal
Sampling point
Time axis setting and roll mode display
If the trigger mode is auto or auto level; T/div is between 100 ms/div and 100 ks/div; and the sample rate is
under 200 kS/s, instead of the waveform display being updated (update mode) by the trigger, the waveform
is displayed in roll mode. In roll mode, the waveform display flows right to left on the screen erasing the
oldest data as new data is acquired. A waveform can be observed in the same way as it is recorded on a pen
recorder. This mode is useful when you are observing a signal which repeats or which fluctuates slowly.
This mode is also useful when you want to detect glitches (fast spikes on a waveform) which occur
intermittently.
Limitation during roll mode display
• When the trigger mode is set to normal or time, the waveform is not displayed in roll mode except when
“Log Start”/“Single Start” is selected from the ACQ menu.
• The operation when “Single Start”/“Log Start” is selected from the ACQ menu is as follows.
By pressing the “Single Start” soft key, the trigger mode (Auto) is set to normal mode. After acquiring
the specified record length of data following a trigger activation, the displayed waveform stops.
By pressing the “Log Start” soft key, the trigger mode is disabled. After acquiring the specified record
length of data, the displayed waveform stops. For the timer trigger, the trigger is activated at the
specified time and the data are acquired once.
• The T/div setting during the roll mode display may sometimes be inadequate for observing the changes
in the waveform on the main area (see page 1-17). In this case, you can use the zoom area to check the
changes in the waveform.
Vertical Sensitivity (For Voltage Modules)
≡
Page 5-4.
≡
The V/div (vertical sensitivity) setting is used to adjust the amplitude of the displayed
waveform so that the waveform can be observed easily.
The V/div setting is made by setting the voltage value per division on the screen grid.
The vertical sensitivity is changed by switching the input section with a different attenuator
having a different damping factor. The setting changes in steps (1 V/div
→
2 V/div
→
5 V/
div...).
1div = 1 V
1div = 500 mV
When V/div is switched from 1 V/div to 500 mV/div
Note
Vertical sensitivity and measurement resolution
To get precise readings, it is recommended that you set the vertical sensitivity so that the waveform’s
maximum and minimum amplitudes are close to the top and bottom of the screen.
This instrument uses a 12 bit (on High-Speed Isolation/High-Speed Modules) or a 16 bit (on High-
Resolution, High-Voltage, Isolation/High-Resolution, Isolation Modules) A/D converters and samples the
input signal with a resolution of 4000 levels (on High-Speed Isolation/High-Speed Modules) or 64000
levels (on High-Resolution, High-Voltage, Isolation/High-Resolution, Isolation Modules). Also, the
waveform is displayed in 500 levels (on High-Speed Isolation/High-Speed Modules) or 8000 levels (on
High-Resolution, High-Voltage, Isolation/High-Resolution, Isolation Modules) per 1 div on the grid.
