External power input vs internal batteri in an Aquadopp

We received this question regarding supplying power to an Aquadopp which applies both to Aquadopp Profilers and Aquadopp Current Meter as well as the Vector:

Regarding switching between the internal battery and an external power source in an Aquadopp:
 a.- How do the instrument recognise the higher (highest) voltage?
 b.- Is the switching made regularly or at the starting time of average measurement ?

The instrument uses diode OR'ing in its input section to select between the two power sources. This means that it will always select the higher of the voltages - instantaneously. So the selection is done automatically, all the time. A couple of examples:

1. If you connect a 15V external supply to the external input of the instrument no power will be taken from the internal battery until external power is removed. The internal battery will then serve as a backup battery and the instrument will immediately start to operate at the internal battery voltage if external power is lost. Note that the external power must then be able to meet the requirements for peak current drain (2-3A).
2. If you connect a 15V battery pack on the external input power the instrument will drain power from the external battery until the voltage has dropped to the level of the internal battery. After that point power will be drained from both batteries.

Best regards,

Sven Nylund