Water Temperature Measurements
Source at /raspberry_pi/rpi_142_sea_temperature/temperature/analysis/index.html
This page links to some measurements of sea, estuary and river temperatures.
- 2022-04-26: Salcombe, Kingsbridge
- 2022-04-20: Exeter Quay, Topsham, Exmouth
- 2022-04-09: Stoke Gabriel, Totnes
- 2022-01-22: Dittisham, Dartmouth
- 2021-11-13: Salcombe, Kingsbridge
- 2021-09-17: River Bure / Wroxham Broad, Norfolk
- 2021-09-15: River Waveney, Norfolk / Suffolk
- 2021-08-24: River Dart, Devon
- 2021-06-29: Exeter Quay, Topsham, Exmouth
- 2021-06-14: Wareham and Poole Harbour, Dorset
- 2021-06-01: Teign Estuary, Devon
- 2021-05-18: River Dart, Devon
- 2021-05-07: River Torridge, Devon
- 2020-10-11: River Fowey, Cornwall
- 2020-09-29: Torbay, Devon
- 2020-09-15: Torbay South, Devon
- 2020-09-08: River Dart, Devon
- 2020-09-04: River Exe and the Exeter Canal, Devon
- 2020-07-17: River Camel, Cornwall
The system uses a semiconductor sensor - DS18B20 - which can measure temperature to ±0.5°C accuracy
from -10°C to +85°C (3 sigma error across devices). It has a resolution of 0.0625°C (1/16°C).
The sensor's response time was measured by moving it between two water-filled temperature baths at 1-minute intervals.
The baths were stirred continuously to simulate the sensor being towed beside a kayak.
The graph below shows three such cycles.
The temperature moved to within 50% of the actual temperature in about 4 seconds,
and within 90% in about 10 seconds.
Temperature (°C) - Time (mm:ss) Graph. Click on image for larger version.
Measurements (shown by dots) are made every 2 seconds.
The sensors are interfaced to a microcomputer (a Raspberry Pi Zero or an Arduino) which
interrogates the sensor every 10 seconds.
The measurements are stored on an SD card.
The microcomputers have a small LED display which shows the date and time
together with the most recent temperature measurement.
The Pi Zero version also runs a web server so that recent measurements can be examined and downloaded.
A small weight was attached to the sensor which was dangled into the water.
The electronics were stored in an orange waterproof bag on the deck of the kayak.
- DS18B20 Temperature Sensor
- DS18B20 Temperature Sensor Library
- UUGear Wide Input Range Power Supply
- Adafruit Mini Led Display
- DS18B20 Temperature Sensor Characteristics
- DS18B20 Datasheet
- Measures temperatures from -55°C to +125°C. (i.e. range of 180°C)
- ±0.5°C accuracy from -10°C to +85°C
- Thermometer resolution is programmable from 9 to 12 bits
- Converts 12-bit temperature to digital word in 750 ms (max.)
- sample data suggest resolution appears to be 0.0625°C (0.06, 0.12, 0.19, 0.25 etc. ...
- ... but 212 = 4096; 180°C/4096 = 0.04°C