Clicking the Measure button initiates the currently selected measurement profile, and it concludes when the profile is completed. The current selected Measurement Profile is shown as the selected item in the drop-down list. This selection can also be adjusted by clicking on one of the 4 predefined quick selects.
Measurement profiles define both:
How a measurement is taken, or the Acquisition process
What data is recorded by that measurement process, or the Operation.
The properties of the selected measurement profile can be edited with this button:
The Single Pt. To SA measurement profile is the most basic laser tracker measurement profile. It defines how a single "Discrete Point" measurement is taken.
In this case the Acquisition builds a single "Discrete Point" made 50 sample taken at a rate of 100Hz or a 1/2 second averaged measurement and returns the best point.
The Operation of the measurement profile then is to send this single averaged or discrete Measurement to SA to be saved in the tree.
The specifics for this Discrete Point's Acquisition profile are as follows:
Points. Specify the number of points you would like to measure. Leave the value at “0” to continue repeating measurements.
Samples/Pt. The number of samples to average together in calculating a single discrete point. This is particularly useful for noisy environments, or cases in which vibration is encountered. This setting proportionately affects the time required for an individual measurement.
PPM Tolerance. Sets the allowable RMS error for measurements based on the distance of the measurement from the instrument. For example, at the default value of 20 PPM, a measurement 7.21m from the instrument would have an allowable RMS error of 7.21m × (20/1,000,000) = 144.2 microns. If after collecting all samples for the point this allowable RMS is smaller than the actual RMS, a Tolerance Exceeded dialog will appear.
Sampling Frequency. The desired rate at which to take samples, in Hz. If this rate is not achievable by the instrument, the closest value will be used. This rate inversely affects the time required to take a measurement. A higher frequency will result in faster measurement. Note that Sampling Frequency, in combination with the Samples/Pt setting, determines the duration of measurement. For example, a discrete point measurement at 50 samples/pt and 100 Hz will result in a measurement time of 0.5 secs
Sample on Controller. Specifies whether the samples are acquired on the tracker controller, or by the instrument interface. Acquiring samples on the controller will often permit a higher sampling frequency, but since SA does not have access to the individual sample data it cannot provide statistical information about the samples unless the controller makes it available.
Front/Back. If checked, each measurement will consist of both front and back face measurements.
Send Ft/Bk Points As. When measuring front face and back face, the individual face measurements can be sent as Separate Obs, in which case they become two separate observations under the target, or as Single Avg Pt, in which the front-face and back-face measurements are averaged together for a single observation.
Auto-Outlier Rejection. If enabled, SA will perform outlier rejection on the samples (see Auto-Outlier Threshold, next).
Auto-Outlier Threshold. The sigma value outside of which samples should be discarded. When measurement samples are collected, SA performs a statistical analysis and determines the standard deviation of the measurements. This value, specified in sigmas, indicates which samples should be thrown away and excluded from the samples used to calculate the average point coordinate. For example, a value of 3 indicates that all samples outside of 3 sigma should be tossed away.
Spatial Scan is another common example of a different acquisition mode.
Spatial Scan measures points spaced by a specified distance. Each time the reflector moves the prescribed distance from the previous measurement, another measurement is triggered. Be aware that this distance will not be perfect, as hardware sampling rate, reflector speed, computer clock speed, network latency, and other factors introduce lag between when the prescribed increment is detected by the instrument interface and when a measurement is taken.
In the above example a button press will start a "stable" measurement profile that will monitor the reflector until it becomes stable and then start measuring. It will then measure at 100Hz (typically modern trackers measure at maximum speed) checking to see if the reflector has moved 0.25" and when it has, it will record a point. This will continue until the beam break.
Start Trigger. Indicates what trigger is to be used to start the measurement profile. After the Measure button is clicked, Button/ delay delays the prescribed number of seconds (in Delay Before Measuring below) before measurement starts. Button/stable waits for the probe to move, then become stable again before triggering measurement.
Delay Before Measuring. Used when Start Trigger is set to Button/delay, the number of seconds to delay before initiating the measurement profile.
Pause @ BeamBreak. If active, the measurement profile will be paused if the beam is broken, and resumed when the beam is locked again.
Stable Recovery. If this option is on, a new stable start condition will be initiated when the beam is re-acquired.
Stop Trigger. Indicates what event is used to signify the completion of the measurement profile. # Points stops measuring when the specified number of points is reached. Beam break stops measuring when the beam is broken. Loop stops measuring when the target loops back to its original measuring position, completing a closed loop.
Increment. For spatial scanning modes, indicates the desired spacing between adjacent measurements.
Points. If the stop trigger is set to the # of points, then this is the total number that will be acquired before the profile stops.
Samples/Pt. Its possible to do a discrete measure at each triggered event. This is not typically used with spatial scan but can be quite helpful with Temporal scans.
The Save and Save As buttons provide the ability to edit the existing measurement profile and save it with new name as needed.
The Iterate this Profile [ ] times option offers the ability to include an automatic repeat. The measurement would then only need to be triggered once and could be executed multiple times one ofter another. This can be quite helpful in repeated part inspections such as inspecting a series of bolt hole patterns for an example.
Additionally, the Acquisition and Operations are selections within a drop-down lists. A new Acquisition or Operation can be selected to modify either the measurement or data recording aspects of the profile.
SA provides a default list of measurement profiles. Measurement profiles can be added and edited and are saved in the persistence file for the particular instrument model. This is typically found in the C:\Analyzer Data\Persistence directory and can be copied between computers as needed. To access the measurement profiles press the folder icon:
These measurement profiles can be sorted by clicking on the column header by name, Acquisition, and Operation used. The Quick Select column shows the 4 designated profiles displayed on the interface for quick access, and the Show column offers the ability to reduce the number of profiles displayed in the measurement profile drop-down list.