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Nie, dziękuję Przekieruj mnie tamhow to check continuity with a multimeter
• De-energise the circuit.
• Turn the multimeter to the “continuity” position (speaker/diode icon) or the lowest resistance range.
• Touch the probes together to confirm the meter beeps/reads ≈ 0 Ω.
• Place the probes on the two points you want to test.
• Beep or ≤ (10-50) Ω ⇒ path is continuous; “OL”, “∞”, or silence ⇒ open circuit.
Electrical principle
• Continuity means a closed, low-impedance path; essentially \(R \lt 50\;\Omega\) for most handheld DMMs.
• The meter applies a small DC excitation (∼0.3–3 V, 0.1–1 mA) and measures resulting current.
Safety first
• Disconnect all power sources, remove batteries, and wait for capacitors to discharge.
• On mains or HV equipment, follow lock-out/tag-out procedures (NFPA 70E, IEC 60364).
• Use CAT-rated leads appropriate to the environment.
Instrument setup
• Leads: black → COM, red → V Ω.
• Dial:
– Continuity: speaker/))) symbol; audible threshold factory-set (typ. 30 Ω Fluke 17x, 40 Ω Keysight U12xx, adjustable on some benchtop meters).
– No dedicated mode? Select the lowest Ω range.
Self-check (lead compensation)
• Short the tips: meter should beep and display lead resistance (0.1–0.5 Ω).
• If your meter supports REL/Δ, press it to null out this offset for more accurate readings.
Performing the test
• Expose clean metal; scrape oxide if necessary.
• Apply probes: polarity is irrelevant except for semiconductors.
• Maintain steady contact—intermittent beeps indicate a loose or fractured connection.
Result interpretation
• Continuous tone / < threshold Ω → good conductor.
• OL / 1 / ∞ / silence → open circuit.
• A numeric value above the beep threshold (e.g., 150 Ω) → partial/high-resistance path; investigate corrosion, cold joints, broken strands.
Component-specific notes
• Fuses: good = beep; blown = OL.
• Switches: continuity when ON, open when OFF (momentary types test both positions).
• Cables/harnesses: probe pin-to-pin for correct wiring, then pin-to-other-pins for shorts.
• PCB traces: follow schematic; lift one leg of the net if parallel components can mask opens.
• Diodes/LEDs: use diode mode; continuity test may show a forward drop but can misidentify reverse leakage.
Common pitfalls
• In-circuit false positives: parallel paths may complete the circuit. Isolate one end when accuracy matters.
• Testing live circuits: risk of meter damage and misleading readings (AC waveform can swamp the continuity detector).
• High-value resistors (>1 kΩ) will register as open in continuity mode—use the Ω range instead.
• Modern DMMs (Fluke 87-V, Keysight U1282A, Brymen BM869s) allow programmable beep thresholds or dual-mode (fast beep + Ω reading).
• Bluetooth-enabled meters stream continuity logs to apps for maintenance records.
• Cable testers and “smart tweezers” integrate continuity plus component ID for field work.
• Auto-scan LCR meters now include 100 kHz/1 mA continuity for high-frequency harness validation.
• Continuity ≠ load test: meters source only a milliamp—enough for detection but too little to reveal micro-arcing joints that fail under load. For critical conductors use a four-wire Kelvin resistance test or voltage-drop under rated current.
• Typical threshold table
| Instrument | Beep ≤ | Test Voltage | Test Current | Notes |
|---|---|---|---|---|
| Fluke 179 | 40 Ω | ≈0.7 V | 0.25 mA | Fast 500 μs latch |
| Keysight U1282A | Programmable 1–1000 Ω | 2.3 V | 1 mA | Also shows live Ω |
| Cheap DMM | 30–60 Ω | 2–3 V | 0.5–1 mA | Slower latch |
• Follow OSHA / IEC safety categories; never defeat safety interlocks.
• Document test results for regulated industries (medical, aerospace).
• Dispose of damaged leads or batteries per WEEE/RoHS.
• Mark the points to probe on schematics to avoid omissions.
• For multi-pin connectors use a “bed-of-nails” or breakout harness to speed testing.
• In production, automate with a continuity jig and a programmable ohmmeter to log pass/fail.
• Continuity testing cannot detect insulation breakdown between adjacent conductors—use a hipot or megohmmeter for that.
• Audible thresholds vary; always read the manual.
• Some sensitive ICs can be latched by the meter’s test current—observe manufacturer cautions.
• Four-wire Kelvin measurements for sub-100 mΩ conductors.
• Time-domain reflectometry (TDR) for locating faults in long cables.
• Combined continuity + insulation resistance protocols per IPC-WHMA-A-620.
Checking continuity involves de-energising the circuit, setting the multimeter to continuity, confirming the meter beeps with the probes shorted, then probing the two test points. A beep/low resistance confirms an intact path; silence/OL indicates an open. While simple, be mindful of safety, meter limitations, and possible false readings due to parallel paths. For critical applications complement continuity with resistance under load or insulation tests.
