5-26
IM 701210-05E
5.14 Setting the Time Base (Internal Clock/External Clock)
Explanation
Selecting the Time Base
Select from the following:
Int: Internal clock signal (TIME/DIV know is valid).
Ext: Clock signal applied to the external clock input terminal (TIME/DIV knob is invalid).
When Selecting Ext
Apply a clock signal of the following specifications to the TRIG OUT/EXT CLK IN
terminal (shared with the trigger output terminal) on the left side panel.
TRIG OUT/
EXT CLK IN
Item Specifications
Connector type RCA jack
Frequency range See Note below
Input level TTL (0 to 5 V)
Valid edge Rising edge
Minimum pulse width 400 ns or more for high and low levels
External clock frequency range 1 MHz maximum.
Rise/Fall time of the clock 2 µs or less
Note
• The upper limit frequency of the external clock is as follows:
701250/701251/701255: 1 MHz
701260/701270/701271/701275: 100 kHz
701280: 25 kHz
701261/701262: When measuring voltage: 100 kHz
When measuring temperature: 500 Hz
701265: 500 Hz
DSP channels: 100 kHz
• If the external clock frequency exceeds the upper limit frequency of the module, sampling
is executed at the upper limit frequency.
External Clock Input Circuit Diagram and Timing Chart
LCX14 or equivalent
EXT TRIG OUT
EXT CLK IN
100 Ω
+5 V
HC245 or equivalent
4.7 kΩ
100 pF
Sample edge
(rising)
400 ns
or more
400 ns
or more
1 µs or more
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