CHAPTER 4 COLLECT
4-7
Allowable Difference
The allowable difference is the range that you allow the readings being averaged to vary from one
another and still be valid. For example, if you set the averaging for 04 readings and set the
allowable difference to .004" (.1mm), then the Dipstick will read the sensor output 4 times,
compute the mean reading (average reading), and determine if any of the 4 readings vary more
than .004" (.1mm) from the mean. If none of the four readings is farther from the mean than your
allowable difference, the Dipstick will save that averaged reading to the SD Card. If one of the
readings is more than .004" (.1mm) away from the mean, the computer will reject it and any
readings that precede it. In this case, the Dipstick will collect readings to replace those that were
rejected, will average the new set, and will compare each of the 4 readings to the new mean. The
desired dimension, in inches for Imperial operation, or in millimeters for metric operation, is
entered into the window. For example, the recommended settings would be entered as ā0.004" in
Imperial operation, and ā0.1" in metric operation.
We suggest that the first time you try averaging, you select 4 readings to average, and an allowable
difference of .004" (.1mm). You may wish to try different settings later.
RUN INFORMATION SETTINGS:
Tapping SETTINGS/RUN INFORMATION will open a dialog box that allows you to set some
default settings for each individual sample measurement line ("Run") of data that you collect.
DATA COLLECTION BIAS
You normally leave this blank. This optional field is where you can enter the Data Collection
Bias for the surface you are measuring. If a fixed Data Collection Bias is to be applied to all runs,
it may be entered here. To learn more about Data Collection Bias, see Chapter 9, DATA
COLLECTION BIAS. This is an optional entry item. You should normally leave this blank until
after you have collected data in a Box, and the program will calculate the Bias and apply it
automatically for you.
DESIGN SLOPE
You normally leave this blank. This optional field is where you can enter the Design Slope for
the surface you are measuring. If a fixed Slope is to be applied to all runs, it may be entered here.
This feature is only used when you are measuring a surface that has a uniform tilt, for example, a
ramp or a drainage pan. This input causes the program to remove (mathematically) the design
slope of an inclined (tilted) surface so you can measure the levelness as if it were horizontal.
The Design Slope input requires input in units of "inches per step or mm per step". If the project
specifications are written in other units, they must first be converted to "inches per step" for the
Imperial version of the Dipstick or "millimeters per step" for the Metric version. Be sure to use
the correct foot spacing when computing this value. See page for a conversion table between
percent slope and inches or mm per step.
You must be careful to ensure that only runs which run straight up or down the slab (the steepest
way) carry the full design slope. You must also be sure to apply the correct sign (+/-) to each run.
Runs that go uphill will require a positive (+) design slope. Runs that go downhill require a
negative (-) design slope. Runs that go across the tilted slab, neither going up nor down, do not
require any design slope. Runs that go up a tilted slab on a 45 degree diagonal will require .707
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