Checkline TI-MINIMAX - Manual (Page 119)

MINI-MAX Ultrasonic Bolt Tension Monitor
Chapter 12 Measurement and the Waveform
Display
12.1 Quantities of Measurement
The MINI-MAX has the ability to measure in a number of measurement
quantities: Time (nanoseconds), Elongation, Load, Stress, and Strain (in terms of
%). While there are a number of quantity options available, the easiest and most
fail safe quantities to consider are Time and Elongation. If Load, Stress, or Strain
will be used on a regular basis, a calibration of the bolts for the specific
application is required.
The equations below outline the required factors and constants necessary for
each quantity. When measuring in terms of time and elongation, very little
information is required, as the measurement is simply a difference equation. The
stress factor and velocity will typically not vary more than 5%, in total, over the
entire range of possible steel fasteners. Therefore the worst case error is 5%.
However, when measuring in terms of load, stress, or strain, the error can be
enormous if errors in effective length, load factor, or cross sectional area are
made. These factors will result in proportional errors overall. Therefore, if the
load factor is off by 10%, the load measurement will be in error by the same 10%
proportionally.
( )( ) [ ]
T V S X
F E
∆ =
0
Elongation
X
E
= Elongation
S
F
= Sonic Stress Factor
V
0
= Material Velocity
∆
T = Change in time.
( )( )
o F E
L L X P
+ =
Load
P = Load
X
E
= ELONGATION
L
F
= Load Factor
L
O
= Load Offset