Water Level Monitoring

Application Notes

Application Background                                                                                                                                                                                          Printer Friendly Version

Water Level Monitoring-Methods

Water level can be measured using any one of the methods below:

  • Method 1 – A shaft encoder / float and wheel / beaded float line system
  • Method 2 – A pressure sensor which is immersed into the stream or river
  • Method 3 – A more complex pressure bubbler system which allows for a small open tube to be immersed into the stream or river with a gas pump or gas cylinder to inject small bubbles into the open tube and measure water depth by measuring the back pressure required to force bubbles out of the tube in the water

There are also emerging technologies such as radar and ultrasonic which can be used to measure water depth.

Water Level Monitoring-Water Level Instrument
Water Level Monitoring-Still Well

While there are many water level monitoring methods / technologies available, the most common and the most stable method is the shaft encoder float and wheel system.
This method required a stilling well or a smaller pipe to be installed on the stream or river bank or on a bridge structure to provide a stable / not disturbed by flow or wind measurement environment for a small float, a float line and a counter weight so the movement in stream / river level can be measured by rotation of the shaft of a wheel. Typically the shaft rotation is measured very accurately by light or laser encoder, and the data is shown on the display and is recorded in the data logger within the instrument.

Application Detail

The Unidata Model 6541C Precision Water Level instrument can achieve operating accuracy and resolution of 0.2mm. This accuracy is maintained for the service life of the instrument without calibration or maintenance, apart from battery changes.

Water Level Monitoring - 6541C Precision Water Level Instrument
Water Level Monitoring Well

The 6541C instrument has the range to monitor surface and underground waters, and the precision to monitor rainfall and evaporation. The very low mechanical friction and inertia of the instrument mean that it can produce data with high precision and accuracy.

Unidata Precision Water Level Instruments have been installed at over 5000 sites. The power consumption of this instrument is tiny, only a few micro amps is needed to operate it, so it can be run on a single battery for more than a year.

Unidata-Water Level Measurement Avon

The 6541C instrument is normally “connected” to the water surface by a float system. On installation, the instrument is set to display the water level. An optical encoder is mounted on the input shaft so, as the water level changes, the input shaft and encoder rotate. The rotation of the encoder is continuously monitored so the instrument tracks water level changes. These changes update the LCD display and are recorded by the instrument’s internal data logger.

Unidata-Water Level Measurement

Your choice of encoding wheel diameter, length of float line, and type of float will depend on the site conditions and measurement objectives.
You can add the additional internal 6541L micrologger assembly and or a neon remote Terminal to provide a temporary store of the data until it is transmitted to a central neon server on a regular basis, perhaps hourly, or more frequently in a flood monitoring application.
When connected with a Neon Remote Terminal or Module you can monitor data recorded by the instrument, you can also reprogram the unit, and check the health of the site, all from a web browser on the internet.

This can be done over cellular or satellite communication links. Using telemetry decreases the need for time consuming site visits.
When you use one of the telemetry options you may need to provide external power such as a solar panel, external battery, and regulator.

Typical Configuration

Options for Application Specific Instruments / InputsUnidata Part NumberDescription
Water Level Instrument6541C-11WLI with 500mm Pulley & Alk Batt Metric (Imperial version available)
Float6541F-115WLI Float - Cylinder 115mm (other options available)
Float Line6541D-MWLI Beaded Floatline Metric (Imperial version available)
Options for Neon Telemetry - NRT / RTU / Field UnitsUnidata Part NumberDescription
Cellular RTU 3G2013F-AB03Neon Metering Module 3G with Antenna and Li Battery
Cellular RTU 4G2013F-AB04Neon Metering Module 4G with Antenna and Li Battery
Cellular RTU 3G - Industrial2016F-AB03Neon Remote Terminal 3G with Antenna and Li Battery
Cellular RTU 4G - Industrial2016F-AB04Neon Remote Terminal 4G with Antenna and Li Battery
Low Earth Orbit Satellite Globalstar2015E-AB0Neon Remote Terminal - Satellite Globalstar Modem with Antenna and three Li Batteries
Ethernet2017E-0B0-1 or 3NRT Ethernet with single or triple Ethernet Ports
with three Li Batteries
Equatorial Orbit Satellite - Inmarsat2018E-AB0-1 or 3NRT Ethernet with single or triple Ethernet Ports
with three Li Batteries
LCD Display2500ENRT LCD Display
NRT Field Termination Strip2103F2015E,2016F,2017E, and 2018E NRT FTS
NRT Firmware Option2303A-8M8M Extended Memory Option
NRT Firmware Option2303A-8M-CAM8M Extended Memory & Serial Camera Option
NRT Firmware Option2303A-CAMSerial Camera Option
Options for Neon Application Software - Customer ServerUnidata Part NumberDescription
Neon Application Software2302ANeon Server Software Licence Incl 5 NAL
Neon Application Software2302A-10Additional 10 NRT Access Licences
Neon Application Software2302A-20Additional 20 NRT Access Licences
Neon Application Software2302A-50Additional 50 NRT Access Licences
Options for Neon Application Software - Unidata ServerUnidata Part NumberDescription
Neon Application Software2301ANeon Data Initial Subscription Setup Fee
Neon Hosting Service2301A-01Neon Data Service Fee for 1-50 NRTs
Neon Hosting Service2301A-02Neon Data Service Fee for 51-100 NRTs
Neon Hosting Service2301A-10Neon Data Service Fee Metering
Options for Conventional Dataloggers / Field UnitsUnidata Part NumberDescription
Standards Starlogger6004D-11Red Logger 512K with Alkaline Battery
Display Starlogger6004D-21Blue Logger 512K with LCD and Alkaline Battery
Prologger7001D-11Green Logger 1M with LCD and Alkaline Battery
Micrologger8010C-EURMicrologger 512K
Starlogger Field Termination Strip6103E6004D FTS
Prologger Field Termination Strip7100E7001D FTS
Starlog V4 Management Software6308A-AUEStarlog V4 Full Licence Key