How to Select Infrared Filters for Motor Overheating Detection

There doesn’t have to be visible damage for a motor to have a heating problem. A bearing may be getting hotter, the load may be too heavy, or ventilation may be poor. A thermal camera lets maintenance staff look for that heat without shutting the machine down. But when it comes to infrared filters for motor overheating detection, buying a filter because it sounds suitable for a thermal camera isn’t enough. The detector has to be able to use the radiation that gets through it.

The filter needs to pass those wavelengths and keep unwanted radiation out of the measurement.

Bodian Optical supplies infrared optical filters for temperature detection and industrial monitoring. Two of its long-pass models, ILP5500 and ILP10000, cover different spectral regions. That difference matters when an infrared instrument is being designed or its optics are being changed.

Why Is Motor Overheating Difficult to Detect Early?

The awkward part is finding a small hot area before the whole machine feels hot. A motor doesn’t warm up evenly, and the view of it can be misleading.

Localized Heat Around Bearings and Motor Housings

Take the bearings and housing: their temperature patterns can differ from those around the windings. Extra friction or a cooling problem may show up in a small spot first, with little obvious change elsewhere.

From the camera’s position, is that spot large enough to distinguish? Resolution and viewing distance affect the answer, as does the temperature difference between the spot and the surface around it.

That is the first question to settle for thermal imaging for motor overheating detection. Decide how small an area needs checking before comparing the cameras’ advertised temperature ranges.

Surface Emissivity and Reflected Heat

A polished housing doesn’t just emit radiation. It can also reflect heat coming from nearby machinery or a heater, so a bright area in the image deserves a closer look.

The camera might be picking up a warm object reflected in the metal instead of a rise in the metal’s own temperature.

Check the emissivity setting and viewing angle against the surroundings before treating that patch as a fault. A reflection calls for a different interpretation from a hot bearing.

Limitations of Visual Inspection

An ordinary camera is useful for dirt, loose components, and damage that is already visible. What it can’t do is measure the thermal radiation used for a temperature assessment.

This is also why a view of a dim factory floor and a thermal view of the same motor provide different information.

The comparison of night vision and thermal infrared imaging explains the difference in detection principles.

How Do Infrared Filters Improve Motor Overheating Detection?

Think about what is being allowed into the detector. A filter admits certain wavelengths and rejects others, but the detector may not respond equally to everything that passes.

For infrared filters for thermal imaging, the question is how much useful signal remains after the interfering wavelengths have been removed.

Isolation of Useful Thermal Radiation

A temperature instrument uses a defined part of the infrared spectrum.

For ILP5500, Bodian Optical specifies a high-transmission area of 6000–13500 nm. Many long-wave infrared detection systems operate in an overlapping region.

That overlap doesn’t establish compatibility on its own. Get the full curve and compare it with the detector response; a filter name or broad wavelength range won’t show every part of the match.

Suppression of Unwanted Short-Wavelength Signals

Shorter wavelengths only enter this particular problem where the detector is sensitive to them.

ILP10000 has a specified blocking region of 200 to 9550 nm. Average transmission across that region is no more than 1%.

That is useful to investigate when an instrument needs longer wavelengths and must keep the shorter ones out.

Don’t carry that blocking figure beyond the stated interval. There needs to be test data for any additional wavelength range.

Transmission Efficiency and Detector Sensitivity

There is another side to blocking: how much of the wanted radiation is lost at the same time?

The peak transmittance specified for both ILP5500 and ILP10000 is at least 75%.

The peak is just one point, though. It doesn’t tell the engineer how much radiation gets through elsewhere in the working band.

For infrared filters for motor overheating detection, look along the whole band used by the detector. A good peak figure can sit beside a less useful transmission curve for a particular instrument.

What Specifications Matter When Selecting an Infrared Filter?

It’s tempting to start with the filter catalog. Start with the detector instead, including its response curve and how it sits in the optical path. That gives the catalog comparison a purpose.

Passband and Detector Compatibility

The high-transmission regions differ between the two models:

• ILP5500: 7500–13500 nm
• ILP10000: 10000–18000 nm

These aren’t two names for the same working range.

Suppose the detector works at approximately 8–14 μm. Much of that band overlaps ILP5500, while ILP10000 leaves out a sizeable part of its shorter-wavelength end. Changing models would change what reaches the detector.

For infrared filter wavelength selection, compare the target radiation, detector response, and filter spectrum together. Looking at any one of them in isolation misses the usable overlap.

Blocking Performance and Substrate Selection

Substrate and blocking range also differ, as the comparison below shows.

Use the table to narrow the candidates, then check them in the intended optical path.

The material name isn’t enough to choose between SI and GE. Wavelength, the other optics, and the working environment have to fit as well.

Filter Dimensions and Operating Conditions

The drawing deserves attention alongside the spectrum.

Will the filter fit without cutting into the field of view? At what angle will radiation hit it? That second question is easy to overlook, yet interference coatings in particular can change their spectral behavior with angle.

Settle the clear aperture, thickness, mount, and operating temperature before signing off a production part.

A later change in the optical layout may mean going back to system testing.

Which Bodian Optical Filter Fits Your Motor Monitoring System?

The same kind of motor can be inspected with different instruments. For that reason, the choice between these Bodian Optical filters belongs with the detector and its working wavelengths, rather than with the motor label.

ILP5500 for Compatible LWIR Thermal Monitoring Systems

The ILP5500 infrared long wave pass filter has an SI substrate, with a specified high-transmission area of 7500–13500 nm.

Its applications include temperature detection, industrial temperature measurement, and thermal radiation measurement systems.

If the detector and the rest of the optics use a compatible LWIR band, ILP5500 gives an industrial motor temperature monitoring project a candidate to test.

Don’t stop at the passband: compare its blocking region with the unwanted radiation in the instrument too.

ILP10000 for Longer-Wavelength Temperature Measurement

The ILP10000 industrial temperature measurement filter has a GE substrate and a specified high-transmission area of 10000–18000 nm.

Thermal radiation analysis and spectroscopy are among its applications.

For an instrument built around longer infrared wavelengths, this is a model to investigate. Its transmission range and blocking below the stated transition region need comparing with that design.

Simply putting it in place of ILP5500 may leave a conventional thermal camera worse off. A detector with little response above 10 μm won’t make much use of radiation that passes at longer wavelengths.

Matching Filter Specifications to Monitoring Requirements

There isn’t a universal choice here for every motor inspection.

For a compatible LWIR requirement, investigate ILP5500. Where the measurement needs longer wavelengths, ILP10000 becomes relevant, but only if the detector can use them.

Bring the measured curves into that decision. Check them against detector sensitivity, expected motor temperatures, and losses through the remaining optics before settling on a model.

What Should Buyers Confirm Before Ordering Infrared Filters?

A part can fit neatly into the housing and still be a poor match for the measurement. Writing down the spectral requirement before ordering helps avoid that situation.

Detector Specifications and Optical Requirements

Give the supplier the detector response range, passband, and blocking requirement. Add dimensions and the expected angle of incidence so the spectral discussion and the mechanical drawing refer to the same setup.

A request that only says ‘thermal camera filter’ leaves those choices open. These details are much more useful when working out how to select infrared filters for an actual instrument.

Sample Evaluation and System Calibration

Put the sample into the assembly where it is meant to work, rather than approving it from a separate component check alone.

Use suitable reference measurements to compare the transmission, image response, and resulting temperature readings.

Don’t assume that an old calibration survives a filter change. If the effective spectral response has changed, the temperature calibration needs checking as part of the sample evaluation.

Technical Consultation and Customization Support

The Bodian Optical specifications give the technical discussion something concrete to work from.

If the size, mounting space, or spectral requirement is unusual, send that detail for review. A requested modification still has to be checked against manufacturing capabilities and the measurement conditions.

Conclusion

A filter for a motor inspection setup needs to suit the detector first. In selecting infrared filters for motor overheating detection, keep the wanted radiation, required blocking, and available mounting space in the same specification.

The choice between ILP5500 and ILP10000 comes down to different transmission ranges. Comparing actual detector data with the filter curves is more useful than trying to choose from the model numbers.

Discuss Your Project Requirements

For a review of a motor monitoring setup, contact Bodian Optical with the detector response curve, dimensions, and target spectral range. Include the operating conditions and mounting restrictions too. Those details make it possible to discuss ILP5500, ILP10000, or a different specification before committing to samples.

FAQ

Q1: What Type of Infrared Filter Is Suitable for Motor Overheating Detection?

A: There isn’t one model for every setup. Match infrared filters for motor overheating detection to the detector’s response and the wavelengths being measured. A long-pass model such as ILP5500 is worth checking for compatible LWIR systems, including both its transmission and blocking curves.

Q2: Can an Infrared Filter Improve Thermal Camera Temperature Accuracy?

A: A well-matched filter can keep unwanted wavelengths out of the reading. It can’t fix a wrong emissivity setting, reflected heat, or a calibration problem, and the rest of the optics still affects the radiation received.

Q3: What Is the Main Difference Between ILP5500 and ILP10000?

A: The ranges and substrates differ: ILP5500 has SI and 6000–13500 nm, while ILP10000 has GE and 10000–18000 nm as its high-transmission area. Check which region the detector can use before choosing between them.