UNI-T UT371 RPM Reading Unstable or No Reading Troubleshooting Malaysia

An unstable, incorrect or missing RPM reading from the UNI-T UT371 Non-Contact Tachometer does not always indicate an instrument fault.

In many cases, the problem is caused by the reflective tape, measuring position, surrounding light or rotating surface. Several basic checks can be completed before arranging further inspection.

Common UT371 Measurement Problems

Users may experience symptoms such as:

RPM reading continuously jumps

Reading is much higher than expected

Reading is lower than the motor nameplate value

Display shows no RPM

Measurement appears only occasionally

Reading changes when the instrument is moved

MAX and MIN values are very different

Results cannot be repeated consistently

The first step is to check the measuring setup rather than immediately assuming that the tachometer is defective.

Check the Reflective Tape

The UT371 detects the reflective marker every time the shaft or component completes one rotation.

Make sure that:

Only one reflective marker is attached

The tape is clean and firmly attached

Oil, dust and moisture are removed

The reflective area is visible throughout the rotation

The tape is not damaged or folded

The surrounding surface is not highly reflective

If two reflective markers are detected during each rotation, the displayed RPM may be approximately twice the actual speed.

Check the Measuring Distance

The recommended target distance for the UT371 is approximately 50 to 200 mm.

If the instrument is too close or too far from the target, detection may become inconsistent.

Hold the tachometer steadily and aim the laser directly at the reflective marker. Avoid continuously changing the angle or distance during measurement.

Reduce Hand Movement

Small movements can cause the laser to miss the reflective target, especially when measuring:

Narrow shafts

Small pulleys

High-speed components

Machinery located behind guards

Targets with limited visibility

If permitted by the workplace safety procedure, use a stable position or suitable support to keep the instrument steady.

Never place the tachometer or your hands close to moving shafts, belts or fan blades.

Check for Strong Surrounding Light

Bright sunlight, flashing lights or reflections from polished metal can interfere with optical detection.

Try the following:

Reduce direct light on the target

Change the measuring angle slightly

Cover unnecessary reflective surfaces

Use a clean, high-contrast target area

Repeat the test from a more stable position

The reflective marker should be clearly distinguishable from the surrounding surface.

Confirm the Correct Rotating Component

A motor nameplate shows the rated operating information, but the connected pump, fan or pulley may rotate at a different speed.

Before comparing results, confirm whether the machinery uses:

Direct coupling

Belt and pulley transmission

Gear reduction

Variable frequency drive

Mechanical speed controller

A different reading may be correct if the measured component is not directly connected at a one-to-one speed ratio.

Check the Battery Condition

Low battery power can affect normal instrument operation.

If the low-battery indicator appears:

Switch off the UT371.

Replace all four AA batteries.

Confirm the correct battery polarity.

Restart the instrument.

Repeat the measurement.

Do not mix new and old batteries.

Why Is the Reading Higher Than Expected?

A high RPM reading may be caused by:

More than one reflective marker

Reflections from surrounding metal

Incorrect pulley ratio assumptions

Incorrect variable speed drive setting

Measuring the wrong rotating component

Remove unnecessary reflective areas and repeat the test using one clearly defined marker.

Why Is the Reading Lower Than Expected?

A low reading may result from:

The laser missing some rotations

Dirty or damaged reflective tape

Excessive measuring distance

Belt slippage

Low motor drive frequency

Mechanical loading

Actual machinery speed reduction

Repeat the measurement after correcting the target setup. If the reading remains low, inspect the machinery and drive system.

When Should the UT371 Be Checked?

Further inspection may be required if:

The laser does not operate

The display is incomplete

Buttons do not respond

Readings remain incorrect with a verified RPM source

The instrument was dropped

Moisture entered the housing

The same problem occurs with different targets

New batteries do not restore normal operation

Checking confirms whether the instrument is functioning correctly. Calibration compares its performance against a traceable reference, while repair is required only when a fault is identified.

Send the Instrument Details First

Before arranging inspection, WhatsApp MTM Precision:

A clear photo of the complete instrument

A photo of the UT371 model label

A photo or short video of the measurement setup

The displayed reading or visible symptom

The expected machinery RPM

This information helps with the initial assessment before the instrument is sent to the Puchong Service Centre.

MTM Precision Sdn Bhd

Showroom & Service Centre: No. 29-1 & 29-2, Jalan Bandar 18, Pusat Bandar Puchong, 47160 Puchong, Selangor, Malaysia

Tel: 03-8080 7172

WhatsApp: +6016-660 7346