6212C Manual Version 15_22 Rev 07-19.docx
Page 20 of 53
Performing Roughness Measurements
Message Type 02
Message Type 02 returns a “rough Ra value”, “smooth Ra value”, “error code”, and “max detector”.
Rough and Smooth Ra Value
Lasercheck uses two different calculation routines to calculate roughness. One routine is optimized and slightly
more accurate for “relatively smooth” surfaces (less
than approximately 10 to 12 microinches Ra). The other
routine is optimized for “relatively rough” surfaces (greater than approximately 10 to 12 microinches). The
“smooth Ra value” should be read and used if surfaces are anticipated / calculated to be less
than approximately
10 to 12 microinches. The “rough Ra value” should be read and used if surfaces are anticipated / calculated to
be more than approximately 10 to 12 microinches.
Common Error Codes
The “error code” generally applies to “smooth Ra” values.
An error code of “ok” is typically returned on a
relatively smooth surface that is correctly aligned (maximum signal found on acceptable detector location for
measurement). An error code of “tc” or “tf” is returned if software calculates that the surface is “too close or
“too far” (max signal found on detector location unacceptable for accurate measurement). These error codes
should be used on surfaces known to be smoother than approximately 15 microinches; they should be ignored
on surfaces known to be greater than approximately 15 microinches as the accuracy of these error messages
declines as surfaces get rougher.
Max Detector
The “max detector” is the same value as “Max Detector Location” discussed above in the “Setup and Alignment”
section and can be u
sed to diagnose “tc” or “tf” alignment error codes.
Recommended Tests and Diagnostics
Negative Ra Value
A “rough” Ra roughness value will be returned so long as the Lasercheck is properly wired and powered. The
only time it might not return a roughness value is if it calculates a negative roughness number. This can happen
if there is a problem with the Lasercheck head or electronics or if there is no surface in position to perform a
measurement. Any of these conditions will generate “noise” instead of actua
l signal from each of the electronic
channels carrying the 35 detector signals. If enough of these noise signals are negative, a resulting negative
roughness value will be generated. Obviously, a negative “rough” Ra value should always be interpreted as an
error condition.
Low sum_voltages and “lv” Error Code
Sometimes, even when a head is not connected, or a surface is not in measurement position, random noise
readings can cause calculation routines to generate a positive Ra value even though it is really
just a “noise”
number. Monitoring the “sum_voltages” value, which is a sum of all voltages from the 35 sensors, as well as the
“lv” error code, can assess this. The "lv” error code will appear when the sum_voltages value is below 300 mV.