Measurement
The Pro-Oceanus Systems Gas Tension Device (GTD) measures the total dissolved gas pressure (millibars).
Description
The total dissolved gas pressure is the sum of the partial pressures of all dissolved gases in the water. By knowing the total pressure of all gases, the partial pressure of nitrogen can be estimated by subtracting the partial pressure of oxygen (several assumptions on the partial pressures of other gases such as carbon dioxide have to be made).
The GTD equilibrates a small sample volume of air trapped behind a semi-permeable membrane with the gases dissolved in the seawater (the membrane is water-proof, but remains permeable to gases). Since this sample volume of air is isolated from hydrostatic pressure, the measured pressure is that solely of the gases in the seawater. This internal pressure is measured using a very stable pressure sensor.
Technical Specifications
| P | P | T (internal) | |
|---|---|---|---|
| Units | psia | mbar | deg. C |
| Range | 0 – 30 | 0 – 2068.43 | N/A |
| Accuracy | 0.006 | 0.41 | N/A |
| Resolution | 0.0006 | 0.04 | N/A |
| Stability/year | 0.006 | 0.41 | N/A |
