Tachometers

A tachometer, also known as a revolution (rev) counter, measures the rotational speed of an object within a machine. The measurement is usually displayed in revolutions per minute (RPM) on either an analog dial or a digital display. Additionally, some tachometers are capable of measuring linear speed and distance.

How Does It Measure?

Contact tachometers take measurements using physical contact, such as through a funnel, wheel or tip. These instruments gather the data for the tachometer. Meanwhile, non-contact tachometers often use a laser or optical disc to measure, making them ideal for mobile applications.

What are the Different Types of Tachometers?

Tachometers are available in various forms, each designed to suit specific measurement needs and applications. Here are some of the common types:

• Analogue: These tachometers use a needle or pointer to indicate the rotation speed on a graduated dial. Simple and cost-effective, they are often used when basic speed measurement is sufficient.
• Digital: For higher accuracy and resolution, digital tachometers provide a numerical readout of the rotation speed on an LCD or LED display.
• Contact: These require physical contact with the rotating object to measure its speed, typically using a rotating wheel or probe that contacts the object's surface.
• Non-contact: To measure speed without physical contact, non-contact tachometers often employ lasers or optical sensors to detect rotation, making them ideal for objects that are difficult or dangerous to access.
• Stroboscopic: Using a flashing light to "freeze" the motion of a rotating object, stroboscopic tachometers allow for visual inspection of speed or for measuring objects with repetitive patterns.
• Photoelectric: These tachometers utilise a light source and a sensor to detect the rotation of an object. They’re often used when high accuracy and resolution are required.
• Hand-held: Hand-held tachometers are portable and easy to use, making them suitable for field measurements and on-site inspections.
• Panel-mount: Designed for installation in control panels or dashboards, panel-mount tachometers provide continuous monitoring of rotation speed.
• Smart: Incorporating advanced features such as data logging, Bluetooth connectivity, and integration with other devices or systems, smart tachometers offer enhanced functionality.
• Magnetic: These tachometers use a magnetic sensor to detect the rotation of a ferrous metal object.

Digital VS Analogue Tachometer

Digital and analogue tachometers differ in several aspects, making them suitable for different applications and user preferences. Here's a comparison of their key differences:

• Display type: Digital tachometers provide a clear and precise numerical display of rotation speed, while analogue tachometers use a needle or pointer on a graduated scale.
• Accuracy: For higher accuracy and resolution, digital rev counters are more suitable compared to analogue ones as they support more precise measurements.
• Ease of readability: With illuminated displays, digital tachometers are easier to read in low-light conditions than analogue tachometers.
• Speed of measurement: Electronic rev counters offer faster measurement updates, providing real-time readings compared to the slight delay in analogue tachometers.
• Power requirements: Analogue tachometers often operate mechanically without external power, unlike digital tachometers, which require batteries or an AC adapter.
• Durability: Due to their simpler construction, analogue tachometers tend to be more durable and resistant to shock and vibration compared to digital ones.
• Cost: Analogue tachometers are typically more affordable than digital tachometers, making them a cost-effective option for basic speed measurements.

Top Features to Look for in a High-Quality Tachometer

When choosing a tachometer, consider these features to ensure it meets your needs:

• High accuracy and precision: Look for a tachometer that provides accurate and precise measurements, especially if your application requires close monitoring of rotation speed. High accuracy ensures that the readings reflect the true speed of the rotating object.
• Wide measurement range: Select a tachometer with a measurement range that encompasses the expected speeds you'll be measuring. This prevents the need for multiple tachometers for different applications.
• Easy-to-read display: A clear display is crucial for quick and accurate interpretation of the measurements. Consider a digital display with large digits or an analogue dial with clear markings.
• Durability: Choose a durable rev counter that can withstand the demands of your work environment, especially if you'll be using it in harsh conditions or industrial settings.
• Non-contact measurement: If your application involves measuring the speed of rotating objects that are difficult or dangerous to access, consider a laser tachometer that uses an optical sensor.
• Data logging capabilities: For applications that require recording and analysing speed data over time, choose a tachometer with an in-built data logger to help you track trends, identify anomalies, and perform further analysis.
• Portable and lightweight: If you need to take measurements in the field or move the tachometer frequently, consider a portable and lightweight design for ease of use and transport.

Tachometer Calibration Procedure

Before using a tachometer for critical measurements, it's essential to calibrate it to ensure accuracy and reliability. Calibration involves comparing the tachometer's readings to a known standard and adjusting it to minimise discrepancies. Here's the general procedure:

1. Prepare the equipment: Gather the necessary equipment, including the tachometer and a calibration standard (such as a calibrated motor or a known speed source).
2. Check the power source: Ensure that the tachometer has a stable power source, whether it's batteries or an AC adapter, to prevent power fluctuations from affecting the calibration process.
3. Select calibration method: Choose a calibration method based on the type of tachometer and the available equipment. Common methods include comparing the tachometer's readings to a calibrated motor or using a stroboscope for visual calibration.
4. Set the tachometer to calibration mode: If your tachometer has a calibration mode, set it to this mode to enable adjustments and ensure accuracy.
5. Compare readings: Run the calibration standard at a known speed and compare its reading to the tachometer's reading. Note any discrepancies between the two.
6. Adjust calibration: If the tachometer's reading deviates from the standard, use the adjustment tools to calibrate the tachometer until its readings match the standard.
7. Verify accuracy: After calibration, measure the speed of the calibration standard again. Ensure that the readings are within the acceptable tolerance.
8. Document calibration: Record the calibration date, the calibration standard used, and any adjustments made. This documentation helps to track the calibration history.
9. Regularly recalibrate: Recalibrate the tachometer periodically or as needed, depending on the frequency of use and the criticality of the measurements. Doing so helps to maintain accuracy and prevent measurement errors.

Industrial Applications of Tachometers

Tachometers are versatile instruments used to measure rotational speed in a variety of industrial settings. Here are some examples of their applications across different industries:

• Machinery: Industrial tachometers are essential for monitoring and controlling the speed of rotating machinery, such as motors, engines, and turbines, ensuring optimal performance and preventing damage due to overspeed or underspeed.
• Automotives: In the automotive industry, RPM tachometers are used to measure engine speed, providing valuable information to drivers and mechanics for monitoring engine performance and diagnosing potential issues.
• Trains: Tachometers are used in trains to measure wheel speed, ensuring safe operation and preventing derailments.
• Laser instruments: Laser tachometers provide non-contact speed measurement, making them ideal for measuring the speed of rotating objects that are difficult or dangerous to access, such as fan blades or turbine shafts.
• Laboratories: Laboratories rely on tachometers for various applications, including measuring the speed of centrifuges and mixers, and for conducting experiments related to rotational motion.
• Marine engineering: The speed of propellers, shafts, and other rotating components in ships and boats are measured by electronic rev counters, ensuring efficient operation and preventing damage.
• Medicine: In medicine, tachometers are used to measure blood flow velocity, providing valuable diagnostic information for cardiovascular health.

Trusted Tachometer Manufacturer, Supplier & Distributor in Australia

RS is a reliable provider of handheld, contact and non-contact tachometers in Australia. We carry a wide range of industrial, digital and laser tachometers from leading brands such as Extech, Compact, SKF, and more.

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