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Appendix E: Tektronix TDS 1002B Oscilloscope

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BW Limit (Bandwidth Limit)

This menu option sets the bandwidth limit of a channel at either the bandwidth of the oscillo-

scope (60 MHz) or 20 MHz. A lower bandwidth limit decreases the displayed noise, yielding a

clearer display, and also limits the display of higher speed details on the selected signal.

Volts/Div

This menu option selects the incremental sequence of the VOLTS/DIV knob as Coarse or Fine.

The Coarse option defines a 1-2-5 incremental sequence. The Fine option helps you change the

resolution by small increments within the coarse settings.

Probe

Use this menu option to match a probe attenuation of 1X, 10X, 100X, or 1000X. A “Probe” is the

device or wire that connects the oscilloscope to the signal source being measured, through the

BNC connector. All probes have an “attenuation factor”— sort of the inverse of a magnification

factor. The probe reduces the input voltage by the indicated factor, therefore to compensate, the

scope must multiply what it detects by the same factor. Probes in this lab will usually be a coax-

ial pair of wires going to a BNC connector, so the choice should be 1X Voltage. Unfortunately,

the factory default setting is 10X Voltage, so after turning on a scope you must check that the at-

tenuation factor set on the scope matches the probe actually attached. If the wrong setting is

used, all oscilloscope voltage measurements will be wrong. There is a PROBE CHECK button on

the scope to determine the attenuation of an unlabeled probe, but usually probes are labeled and

it is faster to set the probe type directly in the corresponding channel menu. Note: When the at-

tenuation switch is set to 1X, the bandwidth of the oscilloscope is limited to about 7 MHz.

Invert

This menu option inverts the displayed waveform vertically with respect to the ground level.

Horizontal Section In the center-right of the scope face is the HORIZONTAL

section. Just as in the vertical sections, knobs control the horizontal scale

(SEC/DIV) and horizontal POSITION. In a single-time-base scope, all the input

channels must be displayed with the same horizontal scale (unlike the vertical

scale). In this dual-time-base scope, a portion of the display can be expanded in a

Window. The window controls are found in the HORIZ MENU. When using the

window feature the main SEC/DIV setting is labeled M and the Window SEC/DIV

setting is labeled W in the display.

Trigger Section Determining when to trigger and display the

next wave-section of the signal is the most complex part of an

oscilloscope. Fortunately, the DEFAULT or AUTOSET settings will

usually work well. Generally you will want to trigger when the wave has reached a

particular LEVEL. But which wave? The TRIG MENU allows you to set the Source:

CH1, CH2, EXT (the signal connected to the EXT TRIG connector in the horizontal

section), EXT/5 (the same signal, but first attenuated by a factor of 5—useful for

large triggering signals), or AC LINE (which uses the 60 Hz, 120 V power line as

the triggering signal—useful for circuits that work synchronously with the line

voltage). Just as in the vertical section, the Coupling of this source to the trigger-

ing electronics can occur in a variety of ways: AC subtracts the dc offset, HF

Reject filters out (removes) high frequency (> 80 kHz), LF Reject filters out low

frequency (< 300 kHz), Noise Reject uses hysteresis to reduce the effects of noise, or DC for

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