Automatic Bottom Sediment Grab Sampler: A Device for Environmental Sampling

What is the purpose of a sampling device that has a projecting stem on a valve rod?

Which sampling device has a projecting stem on a valve rod that opens automatically when the sampler strikes the bottom of a tank?

A. Bottom sediment grab sampler

B. Pressure measuring instrument

C. Velocity measuring instrument

Answer:

The described device is an automatic bottom sediment grab sampler which opens a valve via a stem upon striking the bottom to collect a sample without contamination from above layers.

The sampling device described is likely a type of automatic bottom sampler used in the field of environmental engineering, particularly for taking samples from the bottom of tanks or bodies of water. When this device, often referred to as a bottom sediment grab sampler, touches the bottom, a triggering mechanism causes a valve on top of the sampler to open. This action usually happens through a stem on a valve rod which is held in place by the water pressure or a mechanism that releases upon contact with the bottom. As the sampler seals itself when it is retrieved, the sample inside is maintained without contamination from upper layers.

A similar scientific principle is used in measuring instruments like manometers and air speed indicators, which rely on pressure differences to function. However, the specifics of the device are different as those are not designed for taking material samples but rather for measuring properties such as pressure and velocity.