Q. What do you mean by Piston sampler?

In sampling silts orclays, Piston sampler is lowered into boreholes and piston is locked at bottom of the sampler. This stops debris from entering the tube prior to sampling. After reaching the sampling depth, piston is unlocked so that piston stays on top of the sample going into the tube. Prior to withdrawal of the sampler, piston is locked to prevent the downward movement and vacuum generated during movement of the piston from sampler's end aids in retaining the samples recovered. Sample recovery is increased by using Piston samplers.