Operator's Manual/ Series 7 Salvage Bench Instrument/ No. 0413

Trace

Read this once before you sit down at the bench. It covers the instrument - what every control does and what every mark on the glass means. It does not cover the modules.

Channels
1 (CH2 fitted, not enabled)
Bandwidth
20 MHz
Graticule
10 × 8 divisions
Sweep
20 ns – 500 ms/div
01

What you are doing

Sealed modules arrive on your bench with their labels half gone. Your job is to characterize each one and file a report, and the oscilloscope is the only way to find out what is happening inside.

You cannot open the modules. There are no lights, no sounds, no readouts on them - only numbered test pads. Everything you learn, you learn by putting a probe on a pad and setting the instrument up well enough to see what is there.

  1. Read the work order. The paper tag above the instrument says what needs establishing. It never says how.
  2. Place the probe. Click a pad on the module. This is the only move that costs you anything (§06).
  3. Find the signal. Adjust the controls until the trace is on screen, the right size, and standing still. Turning knobs is free and unlimited - this part is the work.
  4. Read the screen. Count divisions, multiply by the scale (§03).
  5. File the report. Open the tray at the bottom right and type what you measured (§05).
No answers in here

This manual explains the instrument, the same way the manual for any scope does. It will not tell you what a module is doing or how to coax a particular signal into view - working that out from what the screen shows you is the job. Everything you need is on the glass.

02

The screen

Every mark on the glass is telling you something. Learn these six and the instrument stops being mysterious.

CH1 500 mV/div DC TRIG'D 1.00 ms/div TRIG CH1 ↑ 1.50 V VERTICAL SCALE & COUPLING GROUND WHERE 0 V SITS SWEEP STATUS TRIG'D OR AUTO TRIGGER LEVEL AND ITS LINE TRIGGER POINT TIME SCALE SOURCE · SLOPE · LEVEL
Fig. 1 The glass. The two markers on the edges are the ones worth watching: the amber arrow on the left is where zero volts currently sits, and the green arrow on the right is the trigger level. When the level marker sits outside the trace's range it carries an arrow showing which way it has gone off screen.

The status word

TRIG'D means the sweep is locked and the picture is standing still - what you see is repeatable and safe to measure. AUTO means the instrument is drawing anyway because nothing crossed the trigger level; the trace will scatter and overlap itself. HELD means the last good capture is still on screen. NO PROBE means nothing is connected yet.

Do not take a measurement off an untriggered trace. It is not a picture of the signal so much as a pile of unrelated glimpses of it.

03

Reading a measurement

There is one skill underneath everything else here: count divisions, multiply by the scale. The graticule is ruled 10 across by 8 down, with minor ticks every fifth of a division along the centre lines.

CH1 500 mV/div DC 1.00 ms/div 4 DIVISIONS × 500 mV/div = 2.00 V pk-pk 4 DIVISIONS — ONE FULL CYCLE × 1.00 ms/div = 4.00 ms → 1 ÷ 0.004 = 250 Hz
Fig. 2 Amplitude is how many divisions the trace spans vertically, times the volts-per-division readout. Period is how many divisions one full cycle spans horizontally, times the time-per-division readout - and frequency is one divided by that. Measure a cycle from one rising edge to the next rising edge, not edge to edge of a single pulse.

Getting a reading you can trust

  • Make the trace big before you measure it. A waveform two divisions tall can be read to about half a division; the same waveform filling six divisions can be read to a tenth. Turn the vertical scale up until it nearly fills the screen.
  • Frame a whole cycle, and not many more. Twenty cycles crammed edge to edge cannot be counted. Two or three across the screen is about right.
  • Duty cycle is the high time divided by the full period, as a percentage. Both are measured in divisions, so the scale cancels out and you never need the time-per-division figure at all.
  • Check the scale readouts before you commit a number. They are in the corners of the glass, and they are what turns divisions into volts and seconds.
04

The controls

Everything is on one face; nothing is hidden in a menu. Knobs turn three ways - drag up and down, roll the scroll wheel over them, or tab to one and use the arrow keys. Stepped knobs click between fixed positions. Switches cycle when you click the track.

ControlPositionsWhat it does
Vertical — how tall the trace is
VOLTS/DIV5 mV – 10 VVolts represented by one vertical division. It changes how much of the screen the signal uses, never the signal itself.
POSITION±4 divSlides the trace up and down. The ground marker moves with it.
COUPLINGDC / AC / GNDDC shows the signal as it is. AC blocks the steady part and passes only what is changing. GND disconnects the input entirely and shows you where zero is.
PROBE1× / 10×Tells the instrument what the probe divides the signal by. The readouts are only correct when this matches the probe you are actually using.
Horizontal — how much time is on screen
TIME/DIV20 ns – 500 msTime represented by one horizontal division. Ten divisions of it fit across the glass.
POSITION±4 divSlides the trigger point left and right, so you can see further before or after it.
Trigger — whether the picture stands still
LEVELcontinuousThe voltage the signal has to cross for the sweep to start drawing. Its position is marked on the right edge of the glass.
SLOPERISE / FALLWhether a crossing counts on the way up or on the way down.
MODEAUTO / NORM / SGLAUTO draws something even when nothing triggers. NORM draws only when the sweep actually triggers, and holds the last capture otherwise. SGL arms once, captures, and stops.
HOLDOFF40 ns – 10 msHow long the sweep ignores further crossings after it has triggered.
RUN/STOPlatchingFreezes the display so you can measure a capture at leisure. Press again to resume.
SGLmomentaryArms a single capture and stops as soon as it fires.
On the trigger level

The sweep only starts drawing when the signal crosses the level, in the direction SLOPE selects. If nothing ever crosses it, nothing ever starts a sweep at the same point twice - which is what an AUTO trace scattering across the screen is telling you. The level marker on the right edge shows exactly where the threshold sits relative to the trace.

05

Filing a report

The report card sits in the tray at the bottom right. Click it and it slides up over the panel; Esc or Close puts it away again. The instrument keeps running underneath, so you can open it, check a number, and close it without losing your setup.

Values are typed, not chosen from a list. Write them however is natural - the field understands engineering prefixes, so all of these mean the same thing:

Plain

0.08 - volts, no prefix.

Prefixed

80m - 80 millivolts.

With the unit

80 mV - the unit is optional.

Large

5k - 5 kilohertz. Note m is milli and M is mega.

How it is graded

Each field is checked against a tolerance band, not an exact figure - careful division-counting always lands inside it, and guessing rarely does. If a value is disputed, the field comes back circled in red with no explanation. That is deliberate: the circle tells you which measurement to go back and take again, and nothing more.

You can refile as many times as you like, and nothing is lost by getting it wrong. There is no timer and no way to fail.

06

Probe placements

Moving the probe to a different pad is the one action that is counted. Each module lists a par - the number of placements the job is expected to take - and the counter sits under the module well.

Going over par costs you nothing but the mark. It is there to encourage the habit that matters on a real bench: get everything you can out of one test point before you move to the next. Turning knobs, re-scaling, re-triggering and re-measuring at the pad you are already on are all free.

07

Keyboard and comfort

  • Everything is reachable by keyboard. Tab moves between controls, arrow keys turn knobs and throw switches, Space or Enter presses keys. The focused control carries an amber ring.
  • The sweep tells you it is locked four ways - the trace stops moving, the TRIG'D lamp lights, the status word on the glass changes, and there is a sound. You never have to rely on any one of them.
  • Sound can be turned off with the control at the top right. The lock is still obvious without it.
  • Reduced-motion settings are respected. If your system asks for less movement, the instrument drops the glow and the trailing after-images and shows the same information as a still overlay.
  • Nothing is timed. Modules with rare events keep running for as long as you need them to.
08

What is in this build

Two modules, reachable from the case buttons at the top right:

  • Case 03 - The Ripple. Act I, Make it visible. About getting something onto the screen at a size you can actually read.
  • Case 05 - The Runaway. Act II, Hold it still. About making the picture stop moving.

The full instrument is fitted for more than these two use: a second channel, cursors, persistence and probe attenuation are all present in the hardware and will be unlocked by later modules. The controls you can reach now are the ones these two jobs need, plus a few that are simply already on the panel.