Annex
9173B_002-286e-07.10
Page
37
This requirement is found mainly in repetitive measure-
ments in production processes, where good repeatability is
usually sufficient for process monitoring. Accuracy primarily
plays only a subordinate role, when measurements can be
directly related to conforming/nonconforming parts.
For good repeatability, piezoelectric measuring technology
offers the particular advantage that the charge can be dis-
charged with <Reset> before every measurement, enabling
the zero point to be re-determined. Errors due to zero drift
caused by influences changing with time, such as the tem-
perature, are thus basically excluded.
With Kistler piezoelectric measuring chains, a typical repeat-
ability within 0,1 % FSO can be assumed.
9.3
Linearity
Sensor linearity
The quartz crystal produces an electric charge, which is ex-
actly proportional to the load. However, certain unavoid-
able deviations occur due to the mechanical construction of
the sensor. Linearity represents the maximum deviation be-
tween ideal and actual output signal characteristics in rela-
tion to the measurand in a specific measuring range. It is
expressed in percentage of the particular measuring range
limit and is defined according to ANSI/ISA-S37.1 as the
closeness of the calibration curve to a "best straight line"
passing through the zero point:
"Best Straight Line“ – A line midway between the two
parallel straight lines closest together and enclosing all
Output vs. Measurand values on a Calibration Curve.
The best straight line can be determined as follows:
Best straight line – geometric definition
A line midway the two parallel straight lines closest to-
gether and enclosing all output versus measurand values
on a calibration curve. In addition, it must pass through the
zero point based on the assumption that zero measurand
results in zero output signal.
Note: The slope of this center line corresponds to the sensi-
tivity of the sensor. Half the distance between the two par-
allels (measured in the ordinate direction) is the linearity
Summary of Contents for 9173B
Page 1: ...Instruction Manual SlimLine Force Sensor Type 9173B to 9177B 9173B_002 286e 07 10...
Page 2: ...Instruction Manual SlimLine Force Sensor Type 9173B to 9177B 9173B_002 286e 07 10...
Page 27: ...Calibration and Maintenance 9173B_002 286e 07 10 Page 25 Fig 12 In situ calibration procedure...
