Use when: Creating a prioritized, step-by-step multimeter troubleshooting plan for a PCB or circuit based on fault hypotheses. Generates actionable measurement instructions with expected values and safety notes. Messplan, Multimeter, Messanleitung, Prüfplan, Testplan, Spannungsmessung, Widerstandsmessung, Durchgangsprüfung.
Use when: Creating a prioritized, step-by-step multimeter troubleshooting plan for a PCB or circuit based on fault hypotheses. Generates actionable measurement instructions with expected values and safety notes. Messplan, Multimeter, Messanleitung, Prüfplan, Testplan, Spannungsmessung, Widerstandsmessung, Durchgangsprüfung.
<skill_purpose>
Translates fault hypotheses into a concrete, ordered measurement sequence executable with a standard handheld multimeter. Maximizes diagnostic information per step and explicitly handles safety constraints.
</skill_purpose>
- Prioritized fault hypotheses (from `fault_hypothesis_engine` or equivalent)
- Functional block map with critical nodes (from `functional_block_reconstruction` or equivalent)
- Known supply voltage and basic circuit topology
- Optional: Any measurements already performed (to avoid redundancy)
1. Select measurements that provide the highest diagnostic value for confirming or refuting the top-priority hypotheses first.
2. Name measurement points unambiguously (e.g., "J1 pin 1 positive terminal", "collector of Q1", "U2 pin 3 VCC").
3. Specify expected values or expected behavior — not just "check if voltage is present".
4. Explain what a deviation from the expected value means in terms of specific fault hypotheses.
5. Prioritize load-condition voltage measurements when the symptom is load-dependent.
6. Use differential comparisons (two-point measurements) to localize faults — absolute values alone are less diagnostic.
<output_format>
Create or update analysis/05_multimeter_test_plan.md (or the path specified by the user).
Per measurement, use this mandatory table format:
Measurement [N]: [Short descriptive goal]
Field
Content
Objective
[Which hypothesis does this confirm or refute?]
Test points
[Exact probe placement: red probe at X, black probe at Y]
Meter mode
[DC Voltage / AC Voltage / Resistance / Continuity / Diode]
Device state
[DE-ENERGIZED or ENERGIZED — specify load condition if relevant]
Expected result
[Nominal value or expected behavior, e.g., "3.7V ± 0.2V"]
Deviation interpretation
[What does a low / high / zero / infinite reading indicate?]
Safety note
[Short-circuit risk, required precautions, or "None"]
Example (adapt to the actual circuit — do not copy verbatim):
Measurement 1: Battery terminal voltage vs. circuit VCC under load
Field
Content
Objective
Detect contact resistance between cell and circuit input — confirms or refutes cold solder / connector fault
Test points
M1: red=cell(+) terminal, black=cell(-) terminal / M2: red=VCC pad on PCB, black=GND pad
Meter mode
DC Voltage
Device state
ENERGIZED, under normal operating load (motor running or equivalent)
Expected result
M1 ≈ M2 (difference < 0.1V). Difference > 0.3V indicates resistive fault in the path
Deviation interpretation
Drop localized between J1 pins → cold solder or oxidized contact. Drop across trace → PCB trace damage
Safety note
Keep probes clear of adjacent pads — short-circuit risk at close-pitch connectors
Measurement 2: Continuity check across J1 solder joints
Field
Content
Objective
Verify mechanical integrity of battery connector solder joints
Test points
Red probe at J1 pin 1 pad (PCB side), black probe at J1 pin 1 lead (component side)
Meter mode
Continuity (buzzer) or Resistance
Device state
DE-ENERGIZED — remove battery before measuring
Expected result
Buzzer sounds immediately / resistance < 0.5 Ω
Deviation interpretation
No buzzer or R > 1 Ω → cold solder joint or cracked joint confirmed
Safety note
Measure only with power removed — resistance mode requires de-energized circuit
</output_format>
- Resistance, continuity, and diode test measurements: specify device state as DE-ENERGIZED — always state this explicitly.
- Voltage measurements under load take priority when the symptom is load-dependent — schedule these as Measurement 1 or 2.
- Use differential measurements (compare two points in the same current path) to localize the fault segment, not just detect its presence.
- Recommend only measurements feasible with a standard handheld multimeter — no oscilloscope or specialized equipment assumed.
