Hydrometry - Pressure Transducers

Quite a few days have passed since my last post about water level instrumentation, so I should probably mention my source again. Hyrdrometry, 3rd Edition, by Wubbo Boiten. (You can go read the archives if you want an official MLA style citation.) All of the pressure transducer material is based on pages 8-9.

Pressure Transducers:

Three other names commonly used for pressure transducers:
- Pressure Sensors
- Pressure Probes
- Pressure Transmitters

Function:
The basic function of a pressure transducer is to take pressure and turn it into an electric signal. The electric signal is processed, combined with known information about the water density, and converted to a height measurement. The height measurement is typically recorded on a data logger.

Here's a schematic:
Error:
There are a couple sources of error associated with pressure transducers:
1.) Air pressure above the water must be accounted for
2.) Since the pressure transducer is measuring pressure and converting it to water depth, the density of the water is a critical parameter. For instance, salt water has a different density than fresh water. Cold water has a different density than warm water.

Other Concerns:
Pressure transducers may be damaged if exposed to extreme pressures.

Characteristics:
Range: 0-40 feet
Accuracy: 0.1% of the full range