Specification; Introduction; Vertical Deflection System; Triggering - Tektronix 475 Instruction Manual

Section 1—475
SPECIFICATION
Introduction
The 475 Oscilloscope is a wide bandwidth, portable
oscilloscope designed to operate in a wide range of
environmental conditions. The instrument is light in weight
and compact of design for ease of transportation, yet
capable of performance necessary for accurate high- -
frequency measurements. The dual-channel, DC-to-200
megahertz vertical deflection system provides calibrated
deflection factors from 2 millivolts to 5 volts/division. The
bandwidth limiting switch reduces interference from signals
above about 20 megahertz for viewing low-frequency,
low-level signals.
The trigger circuits provide stable sweep triggering to
beyond the bandwidth of the vertical deflection system.
Separate controls are provided to select the desired mode of
triggering for the A and B sweeps. The A sweep can be
operated in one of three modes; automatic triggering,
normal triggering, or single sweep. A variable trigger holdoff
control provides the ability for A sweep to trigger in a
stable manner on aperiodic signals or complex digital
words. The horizontal deflection system has calibrated
sweep rates from .5 second to .01 microsecond/division. A
X10 magnifier increases each sweep rate by a factor of 10
to provide a maximum sweep rate of one nanosecond/
division in the .01 us position. The delayed and mixed
sweep features allow the start of B sweep to be delayed a
selected amount from the start of A sweep to provide
accurate relative-time measurements. Calibrated X-Y meas-
urements can be made with Channel 2 providing the vertical
deflection and Channel 1 providing the horizontal deflec-
tion (TIME/DIV switch fully counterclockwise and VERT
MODE switch to CH 2). The regulated DC power supplies
ensure that instrument performance is not affected by
variations in line voltage and frequency. Maximum power
consumption. of the instrument is approximately 100 watts.
The following instrument specifications apply over an
ambient termperature range of —15°C to +55°C unless
otherwise specified. Warm-up time for specified accuracies
is 20 minutes. The calibration procedure given in section 5,
if performed completely, will allow an instrument to meet
the electrical characteristics listed below.
VERTICAL DEFLECTION SYSTEM
Deflection Factor
Calibrated range is from 2 millivolts to 5 volts per
division in 11 steps in a 1-2-5 sequence. Accuracy is within
3%. Uncalibrated VAR control provides deflection factors
continuously variable between the calibrated settings. Ex-
tends deflection factor to at least 12.5 volts per division in
the 5 volts/div position.
Frequency Response
Bandwidth in both Channel 1 and Channel 2 is DC to at
least 200 megahertz. Risetime is 1.75 nanoseconds or less.
The AC-coupled lower —3 dB point is 10 hertz or less (1
hertz or less when using a 10X probe). Vertical system
bandwidth with the BW LIMIT pushbutton pulled is
approximately 20 megahertz.
Chopped Mode Repetition Rate
Approximately one megahertz.
Input Resistance And Capacitance
One megohm within 2%, paralleled by approximately 20
picofarads.
®
Maximum Input Voltage
DC coupled: 250 V (DC + peak AC) or 500 V P-P AC at
1 kHz or less.
AC coupled: 500 V (DC + peak AC) or 500 V P-P AC at
1 kHz or less.
Cascaded Operation (CH 2 VERTICAL SIGNAL
OUT connected to CH 1 OR X)
Bandwidth is DC to at least 50 MHz with a sensitivity of
approximately 400 1 V/division.
TRIGGERING
Sensitivity
DC Coupled: 0.3 division internal or 50 millivolts
external from DC to 40 megahertz, increasing to 1.5
divisions internal or 250 millivolts external at 200 mega-
hertz.
AC Coupled: 0.3 division internal or 50 millivolts
external from 60 hertz to 40 megahertz, increasing to 1.5
divisions internal or 250 millivolts external at 200 mega-
hertz. Attenuates all signals below about 60 hertz.
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