How to measure coil with multimeter?
A multimeter can verify a coil’s basic health by checking its DC resistance and continuity. For precise inductance values, you’ll typically need an LCR meter or impedance bridge.
Coils appear in a wide range of components—from relay coils and solenoids to transformers and inductors—and the testing approach varies by function. This guide outlines practical, safe methods you can perform with a common multimeter, plus notes on when you’ll need specialized equipment.
Testing a coil with a basic multimeter
Use these steps to assess DC resistance, continuity, and isolation of a coil. This does not measure inductance and should be performed with the coil disconnected from power.
- Ensure the device is powered off and any capacitors are discharged. If the coil is inside a device, disconnect it or isolate the coil from the circuit.
- If the coil has multiple windings (such as a transformer), identify the individual winding terminals and plan which pairs you will test.
- Set the multimeter to the lowest resistance range or to the continuity/beep setting if available.
- Attach the probes to the two terminals of the coil (or the winding pair you are testing) and record the reading.
- Compare the reading to the coil’s specification or to a known-good reference. An open reading (no continuity) usually indicates a broken winding; a reading that is drastically different from the expected value may indicate a fault or poor connections.
- For transformers or multi-winding devices, test between windings to check for unintended inter-winding paths. A measurable resistance between windings often signals a short.
Conclusion: A healthy coil typically shows a finite DC resistance within its specified range and continuity between its terminals. Abnormal readings suggest a fault that may require replacement or further testing in a controlled setup.
Measuring inductance or impedance (when your tool supports it)
If your multimeter includes an inductance (L) or LCR function, you can obtain a rough measurement of a coil’s inductance when the winding is isolated from other components. If your meter does not offer LCR capabilities, you will need a dedicated LCR meter or impedance analyzer for accurate values.
- Confirm the coil is de-energized and disconnected from any live circuit.
- If using L or LCR mode, connect the coil to the meter’s test terminals exactly as you would for resistance testing.
- Choose the appropriate test frequency if the meter allows you to select one (common options are 100 Hz, 1 kHz, or 10 kHz).
- Initiate the measurement and read the inductance value. Note that inductance can vary with temperature and current.
- If possible, repeat the test at multiple frequencies to observe how the coil’s inductance behaves and to identify potential core saturation or parasitics.
Conclusion: Inductance readings help validate coil design and tolerances, but accuracy depends on proper isolation, temperature control, and adherence to the meter’s operating guidelines. For precise inductance, rely on an LCR bridge or impedance analyzer.
Safety and interpretation tips
Always follow safe testing practices. If you’re unsure about the coil’s expected values, consult the manufacturer’s datasheet or an experienced technician. Temperature, mounting, and circuit context can influence readings; treat measurements as indicative unless you’re using calibrated equipment under defined conditions.
Summary
To assess a coil with a multimeter, start with a DC resistance check to confirm continuity and detect obvious opens or shorts. If available, use the inductance or LCR function to gauge inductance, ensuring the winding is isolated from other circuitry. Compare results to the coil’s specifications and consider environmental factors. For rigorous inductance measurements, use an LCR bridge or impedance analyzer. This approach helps diagnose faults in devices ranging from relays to transformers with practical, field-friendly steps.
How do you test a coil with a multimeter?
To again that resistance. Value but we want to go to 20K 20,000 ohms of resistance. Again if you've got an auto ranging multimeter it'll do it for you and you don't have to worry about it.
What resistance should a coil read?
The correct resistance for a coil depends on its type, with typical ranges being 0.4 to 2.0 ohms for the primary winding and 2,000 to 15,000 ohms (or 2 to 15 kΩ) for the secondary winding of a standard automotive ignition coil. For vape coils, lower resistance (sub-ohm) coils produce more vapor, while higher resistance coils create a tighter draw. Always consult the manufacturer's specifications for the most accurate values.
Automotive ignition coils
- Primary winding: A typical range is 0.4–2.0 Ω. A much lower resistance can indicate a short, while a very high primary resistance could cause a weak spark.
- Secondary winding: This resistance is much higher, generally between 2,000 and 15,000 Ω (2 to 15 kΩ), depending on the engine and coil design. Readings in the megaohm range are usually a sign of a problem.
Vape coils
- Sub-ohm coils: These are rated at 1.0 Ω or below and are designed for higher vapor production. They are used for "direct-to-lung" (DTL) vaping and burn liquid faster.
- Higher resistance coils: These are rated at 1.0 Ω or above and produce less vapor, with a tighter, "mouth-to-lung" (MTL) draw.
How to check resistance
- Set your multimeter to the appropriate resistance (Ω) setting.
- Touch the positive lead to one terminal and the negative lead to the other (for primary resistance).
- For secondary resistance, measure between the center post and either the positive or negative post.
- If the reading is significantly higher or lower than the expected range, the coil is likely faulty.
How to measure a coil?
Coil depth is measured by its casing depth in the direction of airflow. Coil height is measured by the number of tubes high in any row. Depth is a function of rows deep, while heigh is a function of tubes in a row.
How to check if coil is ok or not?
Okay. So if I wanted to go further I can take this. Off. Pull these wires out and this is that. One that's cracked big. Time. Let's see if we can get a secondary resistance coming out of this. So.
