Yes, you can measure RPM with a multimeter.
There are different methods to measure RPM, including frequency measurement and period measurement.
One way to measure RPM with a multimeter is by using the frequency measurement method.
To do this, set up the multimeter’s dial to the hertz (Hz) value and connect the black test lead jack to the black ignition coil.
Take the reading value after turning the engine for one minute.
Multiply the value by 60 seconds to get the engine’s RPM. Another way to measure RPM with a multimeter is using an inductive pickup.
For example, you can use Trisco DA 830 and plug the inductive pickup into the multimeter.
Plug the black lead into the COM jack and the red lead into the RPM INDUCTIVE jack.
Turn the measurement mode switch to the RPM position.
It’s important to note that using a multimeter to measure RPM may not be as accurate as using a tachometer specifically designed for this purpose.
However, a multimeter can still provide a rough estimate of the RPM and help diagnose issues with the engine.
What Are The Different Methods Of Measuring RPM With A Multimeter?
To measure RPM with a multimeter, a few methods can be used.
One method is to set up the multimeter’s dial to the hertz (Hz) value and connect the black test lead to the ground and the red test lead to the signal wire.
The Hz reading can then be converted to RPM using a conversion formula.
Another method involves using a multimeter to measure the frequency of the engine-generated signal and then converting the frequency to RPM using a conversion formula.
For example, if using a multimeter to measure RPMs on a 4-stroke engine (without ‘wasted-spark’), the reading must be multiplied by 120, 60 seconds per minute.
If the multimeter has an HZ or FREQ function, it may be possible to calculate engine RPMs with the right amount of fussing and experimentation.
It’s important to note that these methods may not be as accurate as a dedicated tachometer and may require some calibration or adjustment to get accurate readings.
Additionally, it’s worth mentioning that there are other methods for measuring RPM, such as using a handheld tachometer or the tachometer built into the vehicle.
Can You Explain How To Use The Frequency Measurement Method To Measure RPM With A Multimeter?
Here are the steps to measure RPM using a multimeter:
- Set the multimeter to the “Hz” setting, which measures frequency.
- Connect the black test lead to the COM jack on the multimeter.
- Connect the red test lead to the signal source, usually the ignition coil or spark plug wire.
- Start the engine and let it run at a constant speed for at least one minute.
- Read the frequency measurement in the display of the multimeter.
The abbreviation “Hz” should appear to the right of the reading.
- To convert the frequency value into RPM, multiply the frequency by 60 (since there are 60 seconds in a minute) and divide by the number of pulses per revolution.
Note: The number of pulses per revolution depends on the type of engine and the number of cylinders.
For example, a 4-cylinder engine has 2 pulses per revolution (one for each spark plug), while a 6-cylinder engine has 3 pulses per revolution.
Could You Provide More Details On Using An Inductive Pickup With A Multimeter To Measure RPM?
To measure RPM using an inductive pickup with a multimeter, follow these steps:
- Purchase an inductive pickup lead designed for adjustment and diagnosis of RPM.
- Set your multimeter to the “HZ” setting so that it can measure frequency.
- Connect the inductive pickup lead to your multimeter.
- Place the inductive pickup lead around the spark plug wire of the engine you want to measure the RPM of.
- Start the engine and let it run for a minute.
- The multimeter should now display the RPM of the engine.
Some multimeters, such as the Fluke 88V, come with an inductive RPM pickup and can measure RPM in either the DC or AC volts function.
Maintenance meters are available that can read RPM and calculate hours off detection of the electrical emissions from the spark plug wire.
What Are The Limitations Of Using A Multimeter To Measure RPM Compared To A Tachometer?
Using a multimeter to measure RPM has some limitations compared to using a tachometer.
Here are some points:
Limitations of using a multimeter to measure RPM:
- A multimeter can only measure electrical properties, such as voltage, resistance, and current.
To measure RPM, a multimeter must be able to measure frequency, which is not a standard feature on all multimeters.
- A multimeter may load the circuit under test to some extent, which can affect the accuracy of the measurement.
- When using a multimeter to measure RPM on a 4-stroke engine (without ‘wasted-spark’), the reading must be multiplied by 120 to get the correct RPM.
- Some limitations regarding digital multimeters for automotive diagnostics include additional pick-up to measure engine RPM and extreme accuracy is not required for most routine testing.
Advantages of using a tachometer:
- A tachometer is specifically designed to measure RPM and is, therefore more accurate than a multimeter.
- A tachometer can measure RPM on a wider range of engines, including 2-stroke engines and engines with wasted-spark ignition systems.
- A tachometer does not load the circuit under test, which means it does not affect the accuracy of the measurement.
Are Any Other Tools Or Devices More Accurate Than A Multimeter For Measuring RPM?
Yes, some other tools or devices are more accurate than a multimeter for measuring RPM.
Here are some examples:
- Tachometer: A tachometer is a device that measures the rotation speed of a shaft or disk and is designed to measure the revolutions per minute (RPM) of a moving object.
Handheld digital tachometers offer precise rotational speed measurements in various models.
Cheaper models may give you more accurate readings than an average tachometer.
- Digital laser tachometer: A digital laser tachometer is a non-contact electronic tachometer that can measure RPM accurately to +/- 0.02 percent.
- Strobe tachometer: A strobe tachometer is a device that uses a flashing light to measure the RPM of a rotating object.
When choosing a tachometer, consider the following factors: the type of object you wish to measure, whether you need a contact or non-contact device, and the measuring range and accuracy required.
My name is Robert Phillipson, and I am an Electrical Engineer with 20 years of experience in the field. My fascination with multimeters began early on during my career as I was captivated by their precision and accuracy. Over the years, I have gained a deep understanding of how they work, enabling me to use them effectively for measurement applications like testing circuit boards and other components.