Electronics Lab Essentials (7/7): diagnose a bench setup before blaming the circuit

A first electronics experiment sometimes produces “nothing”: no meter reading,
no stable trace, or a value with the wrong sign. Replacing components at random
usually makes the problem harder. A disciplined troubleshooter asks one focused
question at a time.

This self-contained lesson reviews the instruments, then gives you three real Hive
checks. Your job is not merely to obtain the expected result. You must record
what the result proves, what it does not prove, and the next safe check if it
is unexpected. It contains the role map and saved setups needed to work on its
own for the prewired Hive checks. No physical bench or equipment is required.
References to physical instruments are optional theory for later supervised
practice; complete lessons 1–6 first unless your instructor provides equivalent
instrument preparation.

Use this quick role map:

- Breadboard — nodes and paths: Which points are the same node, and is there a complete path? Inspect with power off before changing wiring.
- DC supply — energy and reference: What voltage difference and current limit energize the circuit? Verify output, polarity, reference, and limit before enabling.
- DMM resistance — unpowered path: What resistance or path exists? Keep external power off and connect across the isolated component or network.
- DMM voltage — potential difference: What voltage exists between two nodes? Measure across those nodes while the circuit is normally operating.
- DMM current — branch flow: What current passes through this branch? Power off to insert the meter in series; never bridge a source in current mode.
- Function generator — controlled input: What waveform is applied? Specify shape, frequency, Vpp or amplitude convention, offset, and ground.
- Oscilloscope — voltage versus time: How does the signal change with time? Record probe/reference, coupling, V/div, time/div, and trigger.

Use this sequence in Hive. The physical warning cues in step 6 are optional
theory only; do not attempt to reproduce them without a supervised physical
lab:

1. Power off before changing connections.
2. Inspect: path, node identity, polarity, ground/reference, component value.
3. Predict: expected quantity, approximate value, sign, and unit.
4. Select: instrument, sockets, mode, range, coupling, and probe factor.
5. Connect: correct nodes and common reference; current mode goes in series.
6. Energize cautiously: on a physical bench, watch current and check for heat, smell, sound, or visible distress without touching live parts. In Hive, use the available supply/meter displays, camera view, status messages, and returned measurements; do not claim senses or indicators the remote interface does not provide.
7. Measure and record: include the setting, not only the number.
8. Compare: expected versus observed; change one thing at a time.

For each case, write an expectation before measuring. Then record the observed
result and the next safe check you would make if it did not match. Do not change
the saved circuit wiring.

### Case A — Is the unpowered resistor path complete?

### Case B — Does the powered DC path carry the expected current?

### Case C — Is a known signal generated and displayed sensibly?

Complete exactly three rows. In Next safe check if unexpected, name one
specific check rather than writing “check everything.”

Format-only Case A example: `≈2 kΩ | 2.04 kΩ | yes | supports a complete
approximate series path | with power off, check probe contact`. Replace the
observed value with your own result and complete all three fixed rows. Leave
extra rows unused.

A bounded claim links one result to only the part of the setup it tested. For
example, a resistance near 2 kΩ supports a complete approximate series path,
but does not prove every hidden contact is mechanically sound. A current near
2.56 mA supports the total source-current model, but does not reveal each
parallel-branch current. Two periodic traces with a smaller channel-2 amplitude
support signal generation and attenuation at this saved frequency, but do not
prove the response at every frequency. Use your own measurements—not these
nominal values—as evidence in the table and answer.

A useful lab note lets another person repeat the setup without guessing. Include:

- circuit/preset and node or probe locations;
- supply or generator settings and reference;
- instrument, sockets/mode/coupling, range/scales, and trigger;
- expected value with unit;
- observed value with unit;
- one discrepancy and the next safe check;
- whether the evidence came from real hardware or a fallback.