What are the difference between the fixed and floating ring type consolidometer?

The major differences between fixed and floating ring type consolidometer are as follows:- 

In the fixed ring type, the top porous plate along is allowed to move downwards to compress the specimen. 

while, in the floating ring type, both the top and bottom porous plates are free to move to compress the soil sample

Direct measurement of the permeability of the sample at any stage of the test is possible only with the fixed ring type.

The effect of side friction on the soil sample is smaller in the floating type, while lateral confinement of the sample is available in both to simulate a soil mass in-situ.

The IS-CODE Used for the consolidation test is [IS:2720 (Part XV)—1986]

Fixed ring type consolidometer

floating ring type consolidometer