Pressure (D)

RBR standard instruments with a "D" in the name, such as RBRvirtuoso³ D, RBRduo³ T.D, RBRbrevio³ C.T.D, or RBRconcerto³ C.T.D.ODO.Tu, use piezoresistive pressure (depth) sensors, see Fig. 10.

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Fig. 10.    An RBRconcerto³ C.T.D | deep with a pressure sensor

Overview

The sensor is protected by a clear plastic guard. During deployments, always orient it downwards to reduce debris collecting on the housing.

Specifications

Parameter Value

Range1

20 / 50 / 100 / 200 / 500 / 750dbar (plastic)
1000 / 2000 / 4000 / 6000/ 10000dbar (Ti)

Initial accuracy

±0.05% full scale

Resolution

<0.001% full scale

Typical stability

±0.05% full scale / year

Time constant

<10ms

1 Recommended depth for wave measurements is less than 50m.

The pressure rating of 10000dbar is only available for RBRvirtuoso³ T | deep, RBRvirtuoso³ D | deep, and RBRduo³ T.D | deep.

Calibration equations

Raw pressure

\[P_{raw} = C_0+C_1\cdot VR+C_2\cdot VR^2+C_3 \cdot VR^3\]

where:

\(C_0-C_3\) are unit-specific calibration coefficients determined in the laboratory.

\(VR\) is the measured Voltage Ratio

Temperature compensated pressure

\[P_{meas} = P{cal}+\frac{(P_{raw}-P_{cal})-X_1\cdot (T_{pres}-Tcal)-X_2\cdot(T_{pres}-Tcal)^2-X_3\cdot(T_{pres}-Tcal)^3}{1+X_4\cdot (T_{pres}-Tcal)}\]

where:

\(P_{raw}\) is the uncorrected pressure

\(P_{cal}\) is the nominal pressure while performing the temperature calibration segment
(stored as "X0" in the instrument)

\(T_{pres}\) is the temperature of the pressure sensor

\(Tcal\) is the average temperature during the room-temperature pressure calibration run
(stored as "X5" in the instrument).

\(X_1-X_4\) are unit-specific calibration coefficients determined in the laboratory

Derived parameters: depth, sea pressure, salinity, density anomaly, speed of sound