Manual, F/T Sensor, Data Acquisition (DAQ) Systems
Document #9620-05-DAQ.indd-20
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3.3.2 Offset Correction
Offset correction is a bias vector that zeros out the force and torque data compensating for the
weight of tooling or variation in room temperature. For an example without offset correction the
tooling weight will be seen as a force data on the transducer, using offset correction the force from
the weight of the tool will be zeroed out.
3.3.3 Calibration Matrix
The calibration matrix is the transducer calibration matrix provided on the CD from ATI. This
standard matrix when, multiplied by the biased strain gage data being generated from the
transducer, will provide the force and torque data that can be used for the application.
3.3.4 Gain Correction Factor
Gain correction factor is only required when a customer amplier is being used. The gain
correction factor is used to correct for the customer amplication. Each matrix element is divided
by the gain correction factor to determine the runtime matrix. The calculations required to convert
the strain gage data with customer amplier gain correction into force and torque data is shown in
Figure 3.5.
Figure 3.5—FTMatrixCalculationswithCustomerAmplierGainCorrectionFactor
ST G1
ST G2
ST G3
ST G4
ST G5
bias1
bias2
bias3
bias4
bias5
bST G0
bST G1
bST G2
bST G3
bST G4
GCF1
GCF2
GCF3
GCF4
Runtime Matrix
FyG0
FzG0
TxG0
TyG0
TzG0
FyG1
FzG1
TxG1
TzG1
TzG1
FyG2
FzG2
TxG2
TyG2
TzG2
FyG3
FzG3
TxG3
TyG3
TzG3
FyG4
FzG4
TxG4
TyG4
TzG4
FyG5
FzG5
TxG5
TyG5
TzG5
Divide each Matrix
Element with the Gain
Correction Factor
Bias Vector for
Offset Correction
FxG0
TzG0
GCF0
GCF0
FxG1
TzG1
GCF1
GCF1
FxG2
TzG2
GCF2
GCF2
FxG3
TzG3
GCF3
GCF3
FxG4
TzG4
GCF4
GCF4
FxG5
TzG5
GCF5
GCF5
Determine Gain
Correction Factor
Operations marked RED are to be performed for each measurement sample.
Operations marked BLUE are to be performed only once at the beginning
of a measurement.
Gain Correction Factor = additional gain added
by the customer’s amplifier.
Example 1: customer hardware amplifies by 2-> 1V
becomes 2V -> Gain correction factor = 2
Example 2: customer hardware amplifies by 0.5
(attenuates by 2) -> 1V
becomes 0.5V -> Gain correction factor = 0.5
Transducer
ATI Amplifier
(if included)
Customer’s
Amplifier
Customer’s
Data Acquisition
System
6 gage output
voltages data
Transducer
Calibration
File
Open Excel sheet on the website at
http://www.ati-ia.com/Products/ft/
software/daq_software.aspx, called
“DAQ F/T Manual Calculations”
Working
calibration matrix
Determine Offset
Correction Voltage
bias1
bias2
bias3
bias4
bias5
Note:Temperature compensation is usually not required. Only older
models may need software temperature compensation.
Calibration Matrix
Strain
Gage
Data
Force and
Torque Data
(Fx Fy Fz Tx Ty Tz)
bST G0
bST G1
bST G2
bST G3
bST G4
bST G5
Load in the FTxxxxx.cal file and copy the working matrix
from the spreadsheet to the blue square area.