Tektronix TDS 420A, Service Manual, Page: 31 / 288

Nominal Traits
TDS 420A, TDS 430A & TDS 460A Service Manual
1- 9
Table 1- 4: Nominal Traits — Time Base System
Name Description
Range, Sample-Rate
1,3
2.5 Samples/s to 100 MSamples/s
Range, Equivalent Time or Interpolated
Waveform Rate
2,3
200 MSamples/s to 50 GSamples/s
Range, Seconds/Division 1 ns/div to 20 s/div
Range, Time Base Delay Time 0 to 20 seconds
Reference Frequency, Time Base 100 MHz
Record Length Selection 500, 1,000, 2,500, 5,000, 15,000, and 30,000 points. Record lengths of 60,000 and
120,000 points are available with Option 1M
4
Sampling Edge, External Clock Negative edge, with TTL threshold and tolerances
Hi Res Averaging Period, External Clock Hi Res averaging done over period 1/(maximum external clock rate
5
), but within <100 ns
to 2 s. An external clock edge before this period ends produces an invalid sample.
1
The range of real-time rates, expressed in samples/second, at which a digitizer samples signals at its inputs and
stores the samples in memory to produce a record of time-sequential samples.
2
The range of waveform rates for equivalent time or interpolated waveform records.
3
The Waveform Rate (WR) is the equivalent sample rate of a waveform record. For a waveform record acquired by
real-time sampling of a single acquisition, the waveform rate is the same as the real-time sample rate; for a
waveform created by interpolation of real-time samples from a single acquisition or by equivalent-time sampling of
multiple acquisitions, the waveform rate is faster than the real time sample rate. For all three cases, the waveform
rate is 1/(Waveform Interval) for the waveform record, where the waveform interval (WI) is the time between the
samples in the waveform record.
4
In Hi Res, the maximum Option 1M record length is 60,000 points.
5
You set the maximum external clock rate using the Horizontal Clock menu. The Hi Res samples are averaged over a
10 to 40 ns shorter period than shown by the readout.
Table 1- 5: Nominal Traits — Triggering System
Name Description
Range, Events Delay 1 to 9,999,999
Ranges, Trigger Level or Threshold Source Range g , gg
Any Channel
±
12 divisions from center of screen
Line
±
400 Volts