Single Ended Systems
Designed into each of Kaman's eddy current displacement sensors is a dead zone directly adjacent to the sensor face. This zone is typically referred to as an 'offset'. In most cases this offset is equal to 10% of the calibrated range of the sensor.
The benefit of this offset is that full use of the calibrated range is possible while maintaining a safe distance from the sensor face.
This diagram depicts a standard calibration for single ended systems. Nearly every system that Kaman produces has published performance specifications based on the standard range, offset, and target material specified in the data sheets.
An optional bipolar calibration for single ended systems is shown here. Note that the zero output position does not have to be centered in the range.
Magnetic / Non-Magnetic Distinction
As they pertain to eddy current position sensors, all conductive material can be categorized into 2 groups, magnetic (permeability >1), and non-magnetic (permeability of 1). Note that for eddy current sensors, permeability of up to 1.1 is still considered non-magnetic.
A small diameter sensor (<0.5") set up for a magnetic target will perform poorly (if at all) with a non-magnetic target, (and vice-versa). In most cases electronic bridge components must be changed in order to convert a system set up for magnetic targets to be used with non-magnetic targets. Large diameter sensors (>0.5") typically need only to be recalibrated to the new target material. It is best to check with Kaman's Applications Engineering Group, or Service Group before considering any target changes.
Kaman can provide sensors calibrated to your specific target material. In some instances the exact target (shaft, disc, stage component) should be provided to ensure best possible system performance. When no target material is specified, non-magnetic systems will be set up and calibrated using a 6000 series aluminum target. For magnetic systems, 4130 steel is used.
Refer to the tech note Target Material for a list of materials and their resistivity values.
Contact Kaman for application assistance.