Paradopp and Prodopp Sensor Timing

A customer asked:

Quote

We deployed a number of Aquadopp Profilers off the coast. I need to know when the temperature, pressure, and current measurements are made relative to the sample time.

The sketch below shows when the different sensors are sampled. All sensors are sampled each second except the compass which has a programmable sampling rate.

All sensors except the pressure sensor are sampled between 80 and 100 ms after the start of a 1-s measurement ensemble. The pressure sensor is sampled 10 times and averaged.

The velocity is not sampled in the sensor time slot between 80 and 100 ms.

The recorded measurement time is referred to the start of each measurement interval.

- Gustav

The velocity measurements are done from the beginning of each second until a time given by the measurement load. At 50% load the velocity is measured in the first 500 ms in the figure, at 100% load the velocity is measured continuously.

The time lag between the pressure sensor and the velocity can then found as
T_lag = 1000ms*(Measurement load in %)/200-80
The timing is referred to the pressure sensor so a negative number means that the velocity is measured before the pressure sensor.
For the special case of 2Hz wave measurements you must use 500ms instead of 1000ms to calculate the time lag.

- Sven

Here is a link to the timing diagram:
Paradopp sensor timing
- Sven