Comparison of Hydraulic Cylinder Position Sensing Technologies.

For over a decade the same basic technologies have dominated the landscape of hydraulic cylinder position sensing for harsh environments. Recently a hybrid solution developed by Control Products Inc of East Hanover NJ, has solidly entered the field providing increased reliability and robustness in harsh environmental deployments, and ease of retrofit for the field replacement of existing sensor types.

A comparison of basic sensor types with their relative strengths and weaknesses shows how this new sensor compares to the major Linear Position Sensor Technologies

PropertiesPoten-tiometerMagneto-strictiveLVDTDraw Wire(Optical Encoder)OpticalEncoderCPI SL-Series
Electronics Complexity LowModerateModerateHighHighModerate
Non-ContactingNoYesYesYesYesYes
AccuracyFairExcellentExcellentVery GoodExcellentVery Good
ResolutionFairExcellentExcellentExcellentExcellentExcellent
Temp. RangeFairVery GoodExcellentExcellentExcellentExcellent
Vibration ImmunityFairGoodExcellentFairFairExcellent
Magnetic Field ImmunityExcellentFAIRVery GoodVery GoodVery GoodVery Good
Temp RangeFairGoodExcellentExcellentExcellentExcellent
LinearityModerateVery GoodGoodVery GoodVery GoodGood
CostLowHighModerateModerateHighHigh
Max Stroke Length20”120”20”120”60 in275”
Telescoping CylindersNoNoNoYesNoYes

A Few additional conclusions can be drawn from the table above and a general survey of the field performance of these position sensors.

  • Optical Sensors are the most accurate but can be expensive, require sensitive and complex electronics and are completely unsuitable for high vibration outdoor environments.
  • Magnetostrictive sensors require core drilling of the piston rod to insert.  Every piston length requires a different length sensor rod to be inserted. The longer the rod, the more sensitive it is to vibration, warping, and breakage.
  • Magnetostrictive sensors have poor EMI immunity, affecting accuracy.
  • Only draw wire sensors have characteristics appropriate to telescoping cylinders.
  • CPI sensors boast the longest stroke measurement lengths in this class.
  • By combining noise immune LVDT technology, with the flexible usage configurations inherent to field proven draw wire technology, CPI SL series sensors represent the best set of tradeoffs for robust environmental requirements.

If you have additional questions about our SL series linear position sensor technology, call our team today.