Kaman KDM-8206 - Manual (Page 18)

Kaman Precision Products PART NO: 860516-001
www.kamansensors.com Last Revised: 6/20/2011
18
PART 6 – SYSTEM MODIFICATIONS
6.1 Temperature Compensation
While inductive sensors offer advantages over competing technologies, one of the limitations of this
technology is thermal error due to varying temperature at the sensor location. The effect of
temperature changes can be minimized, but not totally eliminated. These thermal errors appear in
two forms:
1. Thermal Zero Shift – a change in where the output voltage intersects zero on the output
curve. In the KDM-8206 this effect cannot be compensated (reduced), only characterized.
2. Thermal Sensitivity Shift – a change in slope of the output voltage curve. This effect can
be reduced by the temperature compensation process.
Note that the temperature changes referenced apply to the sensor only. The Measuring Module must
be maintained in a temperature stable environment within the temperature band specified.
Thermal sensitivity shift for a standard KDM-8206 system is 0.1% of full-scale output per
o
F (0.18%
per
o
C). A system can be temperature compensated to reduce thermal sensitivity shift to 0.02% of full
scale per
o
F (0.036% per
o
C).
This procedure must be performed at the factory as it involves component changes to the circuit
board. The standard temperature compensation is performed over a 100
o
F (55
o
C) temperature
band .
6.2 Target Material
Each system is individually set up and calibrated at the factory for a specific material. Changing the
target material from the material used for calibration will affect system performance. This is due to
different electrical conductivities and ferro-magnetic properties of conductive materials. When target
material is changed, a calibration adjustment at a minimum is recommended. Reference the
guidelines in section 6.4 for additional system changes that may be required.
6.3 Sensor Cable Length
The sensor cable is part of the inductive bridge circuit. As such, any changes to the cable can affect
system calibration and performance. Some guidelines about modifications to the cable are:
1. Addition of feed through connectors generally does not affect system performance.
2. Small changes to cable length usually require only system recalibration.
3. Contact a Kaman applications engineer for guidance when making changes to the sensor
cable.