The PR-20 portable readouts are mounted in a strong watertight case that contains all the circuitry for reading the transducers, and for refilling the self-contained nitrogen-gas cylinder.
The circuitry consists of the following:
- A nitrogen-gas filled cylinder with a maximum pressure of 14 000 kPa. The cylinder pressure is indicated by a pressure gauge
- A pressure regulator, with the maximum regulated pressure adjusted in the factory to equal the upper limit of the main readout pressure gauge
- An automatic constant low-flow control valve that gives precise and highly repeatable results (available only below the 0–1000 kPa measurement range)
- Either a 105 mm diameter test gauge (model PR-20) featuring an anti-parallax mirror, or a high-precision digital test gauge (model PR-20D)
- A high-flow circuit, for the quick filling of the transducer tubing leads
Reading and Interpretation:
The same circuitry is used in both readout units. The only difference is in the test gauge: the PR-20 has a dial gauge while the PR-20D has a digital gauge. Readings are taken once the transducer tubings are filled with gas and the pressure has stabilized.