DAKOTA ULTRASONICS MAX II Manual

CHAPTER ONE
MEASURING SYSTEM ZERO (CALIBRATION)
1.1 Introduction
In this chapter will be focused on establishing a system zero to enable the group data to
be portable between different hardware devices with limited measuring error. Data
created using one MAX II, can send the data file to another operator for use in another
MAX II, transducer (diameter or frequency), or cable (length or type). The MAX II offers
a few selectable calibration options for flexibility based on preference, or the type of
calibration standard used. Every Max II, transducer, and cable will have a slightly
different system delay because of differences in electronic components and materials.
However small, even identical transducers by diameter and frequency may result in
different delay times. When porting existing data to another hardware set, it's always
optimal to use the same transducer diameter, frequency, and cable length to minimize
potential measurement error. These items should be documented for reference in the
data group.
The sections that follow will outline the procedures for all the System Zero options:
Fixed, Auto, One Point, and Two Point. A system zero is only required if the bolts will
be monitored/measured over the service life of the bolt...measured more than one time
(later date/time). An example might be measuring bolts in a refinery that requires a
shutdown and re-measurement once a year and every year thereafter for the service life
of the bolts. An example when a zero is not necessary is when measuring auto engine
bolts on an assembly line. In the first example one of the calibration options (auto, one
point, two point) would be used, while in the second example the calibration option
should be set to 'fixed'.
A system zero should be done or checked any time the hardware configuration changes
in any way. If the MAX II monitor, transducer, or cable has changed, the zero should be
checked against the current zero calibration group in the project folder
CAL_ZERO_DATA. If the elongation is not reasonably close to "0", then the zero
process should be repeated. Regardless, the operator should always take the time to
verify the system zero prior to starting a job, even when using the same hardware
configuration for existing data.
1.2 Calibration / Zero Misnomer
In the past there have been instances where users were under the impression that
zeroing the unit was the same as calibrating the unit. If the ultrasonic unit could
successfully measure the calibration bars or glass block, the unit could be considered
calibrated. However, this is not the case. The linearity of the unit and material type of
the bolts are not calibrated following a system zero procedure.
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