Contact vs Non-Contact Tachometers: Which Is The Right Tachometer For You?

About Digital Tachometers

A digital tachometer is a handheld device designed to measure the rotational speed of a disk or shaft. This type of instrument expresses results in revolutions per minute (RPM).

Tachometer Applications

Both contact and non-contact digital tachometers have an extensive range of industrial and commercial applications, including measuring shafts, parts and belts on;

• Modes of transport such as cars, planes, trucks, tractors, trains, trams and light rail
• Equipment in processing and manufacturing facilities
• Farm machinery; and
• Research and education.

How to Select a Tachometer Type

All types of tachometers measure RPM, so how do you select the right tool for the job? Consider the following when choosing a tachometer type:

1. Your ability to access and make contact with the equipment to be measured
2. Whether or not it is safe to be close and make contact with the item to be measured; and
3. Whether you need information or parameters other than RPM or total revolutions? Contact tachometers often also measure linear distance and surface speeds rapidly, e.g. moving belts.

Types of Digital Tachometer

Contact Tachometers

Contact tachometers have a freely spinning wheel that directly contacts the rotating shaft to be measured. The tachometer's wheel spins freely, creating pulses interpreted by the tachometer and converted into revolutions per minute (RPM). Due to the method of measurement, many contact tachometers also calculate and display linear speed and distance.

Product example:

LED Display Contact Tachometer, 6" Circumference Measuring Wheel
Product code: IC-DT-107A

The IC-DT-107A allows you to quickly and accurately measure objects' rotational and surface speed using a 6-inch circumference measuring wheel.

Top 3 Features:

1. Built-in memory for last, maximum, minimum and ten separate readings
2. The meter comes with a NIST traceable calibration certificate
3. A complete measuring kit including the 6-inch circumference measuring wheel, funnel tip adapter, shaft extension, batteries, NIST traceable calibration certificate, instruction manual and a foam-fitted carrying case

Specifications:

Display Range: 0.10 to 25,000 rpm with floating decimal

Accuracy:

• 10 to 999.99 RPM: ±0.06 RPM
• 1,000.0 to 9,999.9 RPM: ±0.6 RPM
• 10,000 to 25,000 RPM: ± 0.006% RPM

Measurement Units:

• Per Minute: Revolutions, Inches, Feet, Yards, Meters
• Total: Revolutions, Inches, Feet, Yards, Centimeter, Meters

Non Contact Tachometers

Non-contact tachometers are specialised devices that do not need to make any physical contact with a rotating shaft to obtain a measurement.

Non-contact tachometers comprise a handheld digital unit and an infrared laser source. First, the user applies a small piece of reflective tape to the shaft to be measured. Then, to take a measurement, users align the light beam with the reflective marking tape target. Each time a shaft rotates and the laser meets the reflector, light reflects towards the sensor in the tachometer. The tachometer counts each time and expresses this as total revolutions over a given time, i.e. RPM.

Product example:

Digital Tachometer with Memory includes Min-Max
Product code: DT-48

About:

The DT-48 non-contact digital tachometer is bursting with user-friendly features and useful functions.

Top 3 Features:

1. An extensive measurement range from 2 to 99,999 RPM.
2. Recalls minimum, maximum and last measured values with a single button press.
3. A rapid sample measuring time of 0.5 seconds for RPM measurements over 120.

Specifications:

Display Range: 2 to 99,999 RPM

Accuracy: ±(0.05% plus 1 digits)

Measurement Units: RPM and revolutions

Video: How to Use the Digital Tachometer DT-48

Dual Contact /Non-Contact Tachometers

Find the choice of either contact or non-contact tachometer too limiting? Get complete measurement versatility with a dual contact and non-contact tachometer. These meters have both a contact wheel and a non-contact laser source for complete versatility.

Product example:

Combination Contact & Non-Contact Tachometer
Product code: IC-DT-207LR

About:

The IC-DT-207LR combines the best features found in contact and non-contact tachometers to accurately measure RPM, surface speed, and length. In addition, a screw-in contact adapter makes it quick and easy to convert from non-contact to contact operation.

Top 3 Features:

1. A built-in high-precision laser measures from distances up to 4.2 meters.
2. NIST traceable calibration certificate included
3. The memory stores 13 readings and retains them for 5 minutes. The thirteen stored readings include:
   1. data for the last measurement taken
   2. maximum value
   3. minimum value; and
   4. up to ten measurements.

Specifications:

Display Range:

• Non-contact: 6 to 99,999 RPM
• Contact: 0.8 to 25,000 RPM

Accuracy:

• 6 to 8,299 RPM: ± 1 RPM
• 8,300 to 24,999 RPM: ± 2 RPM
• 25,000 to 99,999 RPM: ± 6 RPM, max.

Measurement Units:

• Per-minute: Revolutions, Inches, Feet, Yards, Meters
• Total: Revolutions, Inches, Feet, Yards, Centimeter, Meters

Conclusion: Contact vs Non-Contact Tachometers

In summary, the point of difference between contact and non-contact tachometers is how measurements are performed. Contact tachometers require access to the rotating shaft to be measured, while non-contact meters only require line-of-sight.

To choose a type of tachometer, consider the following:

1. Your ability to access and make contact with the equipment to be measured
2. Whether or not it is safe to be close and make contact to the item to be measured; and
3. What exactly do you wish to measure? Some contact meters can measure distance and linear speed along with RPM.

Browse all digital tachometers here

Read: How To Choose A Digital Tachometer

For help choosing the best tachometer for your application, speak with an Instrument Choice Scientist: Call 1300 737 871 or email [email protected].