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HMT-MS – Edge Measurement vs Triangular Measurement

Edge Measurement Triangular Measurement
Measurement

Uses an “edge-through” laser and digital CCD receiver.

Measurement

Uses a light source projected on the top of the surface and received by an analog PSD receiver.

Surface

Measurement is not effected by surface colour or reflectiveness.

Surface

Measurement is effected by reflective surfaces effecting both calibration & measurement; reference cylinders must be of a consistent colour to the tested samples. 

Dirty Lenses

Not affected by a dirty lens unless particles are greater than 1mm.

Dirty Lenses

Sensitive to particles on the lens and effected by particles smaller than 1mm.

Accuracy with Temperature Change

< ±0.1mm for ±10 degrees C, tested over ranges from 10 to 30 degrees

Accuracy with Temperature Change

±0.2mm for ±10 degrees C, excluding the effect of the analog to digital converter unit.

Sensor Distance

The distance of measured object to sensor is 500mm, the distance between sender and receiver is less than 500mm, therefore sender and receiver can both be 250mm from the sample.

Sensor Distance

20mm range and a stand off distance of 65mm to capture the received signal. It is not possible to measure the diameter at 90 degrees and have enough gap between the sensors – therefore the sensors are angled at 120 degrees. Typically Standards specify measurement at 90 degrees; therefore it is necessary to get special dispensation if 120 degrees is used.

Calibration

Can be done using push button or PC instruction.

Calibration

Requires manual intervention and movement of pots

Surface Texture

Not affected by craters on the surface of the sample, the colour or reflectivity of the light source

Surface Texture

The received light source data is effected by craters, colour or reflectivity of the sample surface.