Somat eDAQlite, User Manual

Page: 66 / 228

Somat eDAQ
lite
66 I2773-4.
4
en
For a shunt calibration based on a known shunt, enter the shunt resistor and
corresponding engineering value (e.g., a 33.2-kilohm shunt that produces a
2200-pound output). TCE initially highlights the shunt resistor that results in the closest
engineering value. Select the desired calibration step definition based on the strain
values expected in the field.
The equivalent engineering values for the shunt resistors use the following equation.
where, V
e
is the equivalent engineering units value, V
k
is the known engineering units
value,
R
g
is the nominal gage resistance,
R
sk
is the known shunt resistance and
R
se
is the equivalent shunt resistance.
NOTE
Be careful to ensure that the known shunt calibration applies to the same leg of the
bridge circuit that used in the shunt calibration; otherwise, the polarity of the computed
shunt span may be inverted.
A shunt calibration based on the gage and bridge factors calculates a shunt resister
using the gage factor of the active strain gage and bridge factor for the bridge
configuration defined with the channel parameters. Select the desired calibration step
definition based on the strain values expected in the field. The shunt tool assumes that
the engineering units are microstrain. If using dimensionless strain units, divide the
equivalent strain value by 1000000.
The equivalent strain uses the following equation.
where,
E
s
is the equivalent strain in microstrain units,
R
g
is the nominal gage
resistance,
R
s
is the shunt resistance,
G is the gage factor and B is the bridge
factor.
NOTE
If the shunt target results in a downscale shunt,
E
s
is multiplied by -1.
NOTE
Changing the bridge type, bridge resistance, shunt target, gage factor or bridge factor
invalidates the computed equivalent strain. Run the shunt tool again after changing
these parameters.
Multi-Point Cal
The multi-point calibration mode is available for ELBRG and ELHLS channels only.
When beginning a calibration with the multi-point cal mode selected, follow the
instructions on the series of configuration windows to fully define the calibration.
Define anywhere from 3 to 16 calibration points for TCE to acquire and least squares
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