Hydraulic Ram Length Sensing


Thread Starter

Paul McGowan

Does anyone know of analogue devices I can fit to a cylinder to monitor the travel of the ram?

It must be able to survive rough conditions as well.


Steve Bailey

It's pretty common to find hydraulic cylinders fitted with magnetorestrictive linear displacement transducers. Parker, for one, offers them.
Typically we use Parker cyliders with linear feedback built in. The cylinders utilize a rolling pot.
This allows us to read the cylinder position in the P.L.C.

I have done this one way and know of another way which may be possible.

I had a press which shuttled a die set back and forth and needed to know linear position. I used a LVTD connected to the rod end of the cylinder. Most LVTD manufactures have different classes of products ment for different industries. My app. was very dirty, and a lot of vibration. It worked pretty well. Used a sperical rod end coupler at the end of the LVDT for any mis alignment.

Hydroline (Rockford Ill.) offers as a option a internal LVTD which is inside the barrel of the cylinder. Got to think about cost, maintenance, etc. Suitible for most PLC applications.

Good Luck.

Trevor Ousey


You could look at changing the ram to suit an LDT, I have used these on sawmilling equipment with both Temposonic and Balluf transducers. The transducer is fitted into the centre of the ram with the rod having a hollow centre. A magnet is fitted to the piston end and is quite reliable and robust.

Trevor Ousey

Jeremy Pollard

LVDT's might be the best bet. Mechanical issues tho with mounting Resolution might be an issue to.
Have used encoders but depends on the mechanics again

Cheers from:

Jeremy Pollard, CET
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Michael Griffin

If this is a new application, then there are hydraulic cylinders which have linear transducers integrated into them. I haven't used any, so I can't recommend one, but I have seen them in brochures for hydraulic omponents. Try the major hydraulic manufacturers for these.
If this is a retrofit to an existing application or design, then magnetostriction devices are sometimes used for this application. These would be mounted externally to the cylinder. "Temposonic" is one well know brand
name, but there are others as well.

Michael Griffin
London, Ont. Canada