Surface roughness

Please select the from the following questions:

• What type of roughness meter should I use?
• Where can I buy a suitable meter?
• What is Rz and why does the system use it?
• Are there situations where roughness meters should not be used?

What type of roughness meter should I use?

Operation of the SAT relies upon the production of accurate information concerning floor surface microroughness. It is recommended that a portable and robust roughness meter based on the following parameters should be used:

• Roughness Parameter - Rz
• Roughness Unit - μm
• Cut-Off - 0.8mm
• Traverse Length - 4mm
• Stylus -90 degree, 5mm radius diamond tipped

These are typical parameters used by most meters currently on sale. The use of a stylus (similar to that used on a record player) with a diamond tip helps to prevent wear. However, as tips may be fragile, meters should be used with care.

Where can I buy a suitable meter?

Several suitable meters^[28] are currently available.

What is Rz and why does the system use it?

The roughness of floor surface materials has been shown by HSL Scientists to be a useful indicator of their slipperiness in wet conditions; the conditions in which the majority of slips occur. Specifically, the 'Rz Surface Microroughness' has been shown to be a reliable indicator of slipperiness. The calculation of Rz roughness is relatively simple and involves the repeated measurement of the vertical distance between the highest peak and the lowest valley (on a very small scale) within the floor surface test area. The scale used presents this roughness in 'microns', or millionths of a metre.

Are there situations where roughness meters should not be used?

Yes. Roughness meters are accurate and precise scientific instruments, and should be used with care. Meters should not be used on floor surfaces which are wet or contaminated with grease, oils or other materials. Contaminated areas should be cleaned effectively prior to testing. Meters should not be used to assess extremely rough surfaces; doing so can lead to serious damage to the stylus. Similarly, damage may result if meters are used on carpets or other textile floor coverings. Extremes of temperature or humidity can also affect the operation of some roughness meters. Care should therefore be taken to operate them in line with manufacturer's guidance.