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FAQ03292 of Displacement Sensors / Measurement Sensors FAQ

FAQ No. FAQ03292

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What problems occur when measuring hot objects with Z300 High-precision Laser Profiling System?


There are three problems. Heat rays generated from the object are confused with the reflected laser beams received by the Sensor, the ambient temperature around the Sensor rises, and the heat creates a layer of air that is at a different temperature, causing light to be refracted and produce errors.

1. Generation of Heat Rays

Hot objects emit heat rays. These heat rays can cause measurement errors.

The Z300 Sensors use visible red light lasers. There is a filter on the receiver lens which passes through wavelengths of 600 to 720 nm. The CCD receiver element will not accept wavelengths above 1 μm.

Heat rays emitted from the hot object are similar in wavelength to the laser beam, so the receiver element may detect the heat rays. Conduct tests with the actual system to determine how much it is affected by heat rays.

ZX-L Laser Displacement & Measurement Sensors and Z500 Profile Measuring System face the same problem.

Laser wavelengths of the main Displacement Sensors are as follows: Z300-S2: 650 nm, Z300-S5 and Z300-S10: 670 nm, Z300-S60: 658 nm, Z500-SW2: 650 nm, Z500-SW6 and Z500-17: 658 nm, all models of ZX-L: 650 nm.

2. Rise of Ambient Temperature around the Sensor and the Temperature of Sensor Itself

There may be a heat-related problem. Check the ambient temperature specification in the catalog and install a cooling device (such as a fan) to make sure that the temperature stays within the specified range.

Additional Information: Make sure that cooling is applied regularly to maintain the ambient temperature around the Sensor at a certain level. If the cooling is turned ON and OFF, the Sensor casing and mounting board may expand and contract due to the temperature change, causing measurement errors.

3. Measurement Error Due to Refraction of Light

A layer of hot air forms around the hot object, but the air surrounding the Sensor is at room temperature. This forms a temperature gradient between the two locations, which is equivalent to a gradient in air density. Light is refracted where the densities differ. The Z300 uses triangulation, so refraction of light will lead to a measurement error.

If you want to measure a hot object, check first whether these Sensors can be used to make measurements to the required accuracy.