Why UNI-T UT306C Gives Inaccurate Readings on Metal Surfaces Malaysia

A common problem when using the UNI-T UT306C Infrared Thermometer is obtaining a temperature reading that appears too low, too high or inconsistent when measuring metal.

This does not always mean that the thermometer is faulty.

Infrared thermometers measure the infrared energy emitted from a surface. Shiny metals such as aluminium, copper and stainless steel emit infrared energy differently from painted, oxidised or non-reflective surfaces.

Incorrect emissivity, surface reflection, measuring distance and target size can all affect the result.

Common Symptoms of an Incorrect Reading

Users may notice that:

The reading is much lower than expected
The temperature changes when the measuring angle changes
The reading changes when the operator moves position
Similar metal components show inconsistent temperatures
The infrared result does not match a contact probe
A shiny pipe appears cooler than the insulation beside it
The reading changes when nearby equipment becomes hot
The temperature appears unstable even when the target is stable
The result changes significantly at different distances

These symptoms may be caused by the surface and measurement method rather than an internal UT306C fault.

How an Infrared Thermometer Measures Temperature

The UT306C detects infrared energy emitted from the target surface.

The instrument then converts this detected energy into a temperature reading according to the selected emissivity value.

A surface with high emissivity emits infrared energy efficiently. A low-emissivity surface emits less energy and may reflect more infrared energy from surrounding objects.

This is why two surfaces at the same actual temperature can produce different infrared thermometer readings.

What Is Emissivity?

Emissivity describes how effectively a surface emits infrared energy compared with an ideal reference surface.

The value is expressed from 0 to 1.

The UT306C allows emissivity adjustment from 0.10 to 1.00, enabling the user to adapt the instrument to different target materials.

Materials such as these are generally easier to measure:

Painted metal
Oxidised metal
Rubber
Plastic
Wood
Paper
Concrete
Non-reflective surfaces

Materials that may be more difficult include:

Polished aluminium
Bare copper
Stainless steel
Chrome
Galvanised metal
Shiny metal pipes
Reflective panels

The correct setting depends not only on the material but also on its surface finish, oxidation, coating and condition.

Why Shiny Metal Is Difficult to Measure

A shiny metal surface may have low emissivity and high reflectivity.

Instead of mainly emitting its own infrared energy toward the thermometer, the surface may reflect infrared energy from:

The operator
Nearby machinery
Lighting
A hot motor
A cold wall
Sunlight
Heating equipment
The surrounding ceiling

The UT306C may partially detect this reflected energy and display a misleading temperature.

The problem can become more noticeable when the operator changes position because the surface reflects a different part of the surrounding environment.

Example: Measuring a Stainless-Steel Pipe

A technician aims the UT306C at a shiny stainless-steel pipe and obtains a reading that appears too low.

After changing the measuring angle, the temperature increases. When the technician moves closer, the result changes again.

Possible causes include:

Incorrect emissivity
Reflections from surrounding surfaces
Measurement spot larger than the pipe
Different background temperature
Measuring at an unsuitable angle

The reading should not be accepted without checking the measurement conditions.

Use a Non-Reflective Reference Surface

One practical method is to create a suitable non-reflective reference area on the target.

Depending on the application and site procedure, this may involve:

Applying suitable non-reflective tape
Using a safe high-emissivity surface coating
Measuring an existing painted section
Measuring an oxidised section of the same component

Allow the tape or coating to reach the same temperature as the target before taking the reading.

Do not apply tape or coating to a surface when:

The surface is excessively hot
The equipment is moving
The component is energised and unsafe to approach
The material could damage the equipment
The site procedure does not permit it
The application involves hygiene-sensitive surfaces

Safety and equipment requirements must take priority.

Adjust the UT306C Emissivity

The UT306C allows the emissivity value to be changed between 0.10 and 1.00.

When the target material and surface condition are known, select an appropriate value based on reliable reference information.

Avoid assuming that every metal uses the same emissivity value. Painted steel, oxidised steel and polished steel can behave very differently.

If the exact emissivity is unknown, users can compare the UT306C reading with a reliable contact-temperature measurement on the same surface under stable conditions.

The emissivity setting can then be adjusted so that the infrared result corresponds more closely with the reference measurement.

Compare with a Contact Probe

A contact probe can provide a useful reference when infrared readings are uncertain.

A practical comparison method is:

Allow the target temperature to stabilise.
Attach or place a suitable contact probe on the surface.
Allow the probe reading to stabilise.
Measure the same area with the UT306C.
Maintain a suitable distance and angle.
Adjust the emissivity if appropriate.
Record the final setting and surface description.

The contact probe itself must be suitable for the surface, temperature range and application.

Differences may still occur because the two instruments use different measuring methods and may not detect exactly the same area.

Check the 12:1 Distance-to-Spot Ratio

Incorrect readings may also occur when the measurement spot is larger than the metal target.

The UT306C has a 12:1 distance-to-spot ratio.

Approximate spot sizes include:

At 120mm, the spot is about 10mm
At 600mm, the spot is about 50mm
At 1,200mm, the spot is about 100mm

If the user measures a 20mm pipe from 600mm away, the measurement spot will include the pipe and the background.

The displayed temperature will therefore represent a combination of the detected surfaces.

Move closer until the target is larger than the measurement spot, provided it is safe to do so.

The Circular Laser Does Not Define an Exact Boundary

The UT306C uses a circular laser to help the user aim at the target area.

The laser provides useful visual guidance, but it should not be treated as a laboratory-precise boundary of the measurement spot under every condition.

Users must still consider:

Measuring distance
Target size
Surface shape
Measuring angle
Infrared reflection
Emissivity

The circular laser does not compensate for incorrect emissivity or a reflective surface.

Avoid Measuring at a Sharp Angle

For more consistent results, aim as close as reasonably possible to the surface rather than measuring at a very sharp angle.

A sharp angle can:

Increase the effective measurement area
Include nearby surfaces
Increase reflection effects
Reduce repeatability
Make the target position less clear

This is especially important for narrow pipes, metal edges and curved components.

Always maintain a safe position around hot, moving or electrical equipment.

Do Not Measure Through Glass

An infrared thermometer normally cannot measure the actual object temperature through ordinary glass.

If the UT306C is aimed through a glass panel, it may measure:

The glass surface
Reflected infrared energy
A combination of surrounding thermal effects

This is important when checking:

Electrical panels
Oven doors
Refrigeration display cases
Machine windows
Protective enclosures

A visible object behind glass is not necessarily measurable with a standard infrared thermometer.

Environmental Factors That Affect Readings

The measurement can also be influenced by:

Steam
Smoke
Heavy dust
Condensation
Strong sunlight
Rapid temperature changes
Nearby heat sources
Airflow across the surface
A dirty infrared sensor
Moving from a cold room into a warm humid area

If condensation forms on the thermometer or target, allow conditions to stabilise before measuring.

Why Readings Change with Distance

The reading may change with distance when:

The target is smaller than the measurement spot
The background has a different temperature
The user aims at a different part of the surface
The target is curved
The laser circle is not centred consistently
Surrounding reflections enter the measured area

For repeatable monitoring, use approximately the same distance, angle and target location each time.

Why Readings Change with Measuring Angle

Reflective metal can behave like an infrared mirror.

When the UT306C is aimed from a different angle, the target may reflect a different surrounding object. The displayed temperature can therefore change even when the metal itself remains at the same temperature.

If the reading changes significantly with angle, check for:

Shiny surface finish
Nearby hot or cold objects
Incorrect emissivity
Small target size
Curved metal surfaces

A non-reflective reference area may provide a more stable result.

Infrared Thermometer or Thermal Imager?

A thermal imager also relies on infrared measurement and can experience similar emissivity and reflection problems.

A thermal image may make the temperature pattern easier to understand, but it does not automatically make shiny metal measurements accurate.

Users of both instrument types must consider:

Emissivity
Reflected temperature
Surface material
Measuring angle
Target size
Environmental conditions

For precise surface-temperature work, a suitable contact probe may still be required.

When the UT306C May Require Checking

The UT306C may require inspection if:

Readings remain abnormal on suitable non-reflective targets
The instrument gives inconsistent results under stable conditions
The displayed reading changes without changing the target
The unit has been dropped or exposed to moisture
The infrared sensor window is damaged
The instrument disagrees significantly with a reliable reference across several suitable targets
The display or controls do not operate normally

Before concluding that the thermometer is faulty, test it on a stable, non-reflective surface with known or independently checked temperature.

Quick Troubleshooting Checklist

When a metal-surface reading appears incorrect, check:

Is the surface shiny or reflective?
Is the emissivity setting suitable?
Is the target larger than the measurement spot?
Is the thermometer too far away?
Is the measuring angle consistent?
Is a nearby hot or cold object being reflected?
Is the reading taken through glass?
Is condensation present?
Can a non-reflective reference area be used?
Can the result be compared with a contact probe?

Correcting these factors can often improve measurement consistency without changing the instrument.

Using the UT306C Correctly in Malaysia

The UT306C is suitable for factory maintenance, HVAC inspection, refrigeration work and general surface-temperature screening across Malaysia.

Its adjustable emissivity provides flexibility for different materials, but users must understand that shiny metals remain challenging for infrared measurement.

Correct target preparation, measuring distance and comparison technique are essential for obtaining useful readings.

Enquire About UNI-T UT306C Measurement Problems

If your UNI-T UT306C gives unstable or unexpected readings, WhatsApp MTM Precision a clear photo of the thermometer, model label, target surface and displayed result for an initial assessment.

Please also state the target material, approximate temperature and measuring distance.

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
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my

Why UNI-T UT306C Gives Inaccurate Readings on Metal Surfaces Malaysia