water level loggers vented vs absolute. definitions absolute: measures total pressure (weight) above...
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![Page 1: Water Level loggers Vented vs Absolute. Definitions Absolute: Measures total pressure (weight) above the sensor. Atmospheric pressure must be removed](https://reader036.vdocuments.mx/reader036/viewer/2022062716/56649e155503460f94b00117/html5/thumbnails/1.jpg)
Water Level loggersVented vs Absolute
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Definitions
Absolute: Measures total pressure (weight) above the sensor. Atmospheric pressure must be removed from this value to reveal actual water pressure (water column).
Vented: Measures only water pressure above sensor. Atmospheric vent accounts for atmospheric pressure.
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The mystery of barometric compensation
Pressure in cmH₂OLevel logger: 1500cmH₂O – Baro: 1000cmH₂O = 500cmH₂O
= 0.5m above the pressure sensor
ALWAYS take a manual dip measurement!
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How do they work?5cm
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Baro
Absolute
2 x Errors
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Pressure ranges
1m --------------------------------------------------------------------------------------
10m --------------------------------------------------------------------------------------
30m --------------------------------------------------------------------------------------
Sensitivity varies with manufacturer. Accuracy based on full scale.
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One size does not fit all…..High Accuracy?
100m range?
Low maintenance?
Easy to deploy?
Multiple interface options?
Long battery life?
Low cost?
120
UbUnobtanium
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If vented loggers are so good, why would I choose not to use them?
Vented cable: installation, vandalism, weather protection, tailor length cables/re-deployment
Cost
User interface
Maintenance
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When should I use a vented logger?
Critical data
External logger or telemetry?
Single installation?
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Why would I choose to use an absolute logger?
Maintenance free
Easy deployment
Low cost, particularly for multiple installations
Purpose made intuitive interfaces
Easy re-deployment/Versatility
Discrete
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What else to consider?Site access?
Equipment placement (above and below water)
Environmental/human risk?
Return visiting?
GPRS signal? (NOT THE SAME AS CALL SIGNAL)
Critical data?
Expected fluctuation?
Other parameters?
Budget?
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Conclusion
Is vented better than absolute? … Not necessarily
Consider your application carefully