Section 5 | Sample Battery Lifetime Calculations
©
2022
– Valeport Ltd
Page | 8
5. Sample Battery Lifetime Calculations
5.1. Calculations - Based on Memory
Lifetime based on memory is dependent on the sensors fitted. All parameters use 2 bytes of
memory per sample, with the exception of the optional sound velocity sensor which uses 4 bytes.
With a typical configuration of Speed, Direction and Pressure, lifetime can be calculated as follows:
Total memory used per record is 2 x 3 = 6 bytes.
In Profile mode, each record is also assigned a date/time stamp, which uses a further 7
bytes.
The 16 Mbyte memory actually contains 16,777,216 bytes. Allowing a small amount of memory
usage for header files, the memory will store over 1.2 million records in Profiling mode, and over
2½ million records in other modes. The length of time that this memory will last for obviously de-
pends on sampling scenario. Here are three examples:
Continuous Data Sampling - 8Hz
•
Memory used per second is 6 x 8 bytes = 48 bytes
•
Total memory fitted is 16,777,216 bytes
•
Seconds before memory full is 16,777,216 / 48 =
349,500 seconds
approximately
-
equivalent to 97 hours
•
This period could be doubled by sampling at 4Hz
Burst Sampling - 4Hz
Sampling 1 minute in every 10 minutes | recording all data points:
•
Memory used per burst is 6 bytes x 4Hz x 60 seconds = 1440 bytes
•
The memory will be full after 16,777,216 / 1440 bursts = 11650 bursts
•
At a 10 minute cycle time, this is 116500 minutes
-
equivalent to 80 days.
Profiling
5000m cast | measuring every metre
•
1 reading every metre of both descent and ascent
•
This means 5000 data points descending, and a further 5000 ascending
•
Each record consists of 6 bytes of data and 7 bytes of time stamp
-
Each record therefore uses 13 bytes
•
A single cast will take 10,000 such records and will therefore use 130,000 bytes.
•
The 16Mbyte memory will therefore hold approximately
125 casts
worth of data.
