SlimLine 9173B, Instruction Manual

Page: 38 / 44

SlimLine Force Sensor, Type 9173B to 9177B
Page 36 9173B_002-286e-07.10
9.2 Measurement Uncertainty
Systematic errors, accuracy
Accuracy is the extent of the conformity between a meas-
ured value and a true value of the measurand. In a piezo-
electric measuring chain it is determined by many syste-
matic errors, such as

Sensor linearity

Sensor hysteresis

Crosstalk from other measurands

Charge amplifier linearity

Disturbance (forces, moments)

Disturbance (environmental influences, like temperature)

Duration of the measurement

etc.
Experience with a measuring chain consisting of sensor,
cable and charge amplifier shows that an accuracy in the
range of 1 ... 2 % of the measuring range is achieved. This
value does not include errors due to influences from exter-
nal sources acting on the measuring chain, due to me-
chanical adaptation of the sensor and environmental influ-
ences. For the highest accuracy requirements, we recom-
mend calibration of measuring ranges specific to the appli-
cation.
Measurement uncertainty of charge amplifiers
When random and systematic errors together are quanti-
fied as variance, measurement uncertainty can be derived.
With charge amplifiers, this mainly depends on type. The
following typical values apply:
Laboratory charge amplifier

0,2 ... 0,5 % FSO
Industrial charge amplifier

1 % FSO
Higher accuracy can be achieved with the following proce-
dures:

Calibration in the Kistler factory

Calibration with charge amplifier Type 5395A

Restriction of the temperature range
Random errors , precision, reproducibility
Precision or reproducibility is the extent of conformity
between independent data measured under specified con-
ditions.
Repeatability
Repeatability is understood as "serial precision" for exam-
ple conformity between several measurements in sequence
under largely unchanged conditions.