The instrumentation group's attempts to support this activity have had limited success, mainly due to constraints on time and personnel. The situation might change in the future, so these web pages are kept as reference.

Water level & temperature recorder

• ± 5000 mV
• ± 2500 mV
• ± 250 mV
• ± 25 mV
• ± 7.5 mV
• ± 2.5 mV

• ± 0 - 2.5 V
• ± 0 - 10 V
• ± 0 - 25 V

• Specs
• Brochure
• Overview

• Specs
• Brochure
• Overview

• Intab manual

• CR 800: NOK 12860
• CR 850 (w/display and keyboard): NOK 15860

• Tinytag Plus Re-Ed (8 bit) IP 68: SEK 1990
• Tinytag Plus Re-Ed (8 bit) OEM: SEK 1490

• Aanderaa Instruments, Select "Products", then "Environmental Monitoring Stations":
• Ultrasonic Sensor 3600 (for above surface installation) or Pressure Sensor 3191 for underwater installation)]]

Water level sensor types

• Sensor types (quoting from their web page)
  • Groundwater level, in deep observation wells: 6-wire resistive gages or vibrating wire pressure transducers
  • Groundwater level, in more shallow water applications: Piezometers, bubblers, or float and pulley systems
  • Surface water level, "measurements are often made in a vertical stand-pipe (stilling well) installed adjacent to a lake, river, or stream". "A float and pulley is often used, but pressure transducers, ultrasonic, and resistive tape sensors work well also ..."
  SR50-L "Ultrasonic Distance Sensor"
• Measurement range: 0.5 - 10 m
• Accuracy: +/- 1 cm, or 0.4% of distance to target (whichever is greatest)
• Operational accuracy: 1" (2.54 cm) typ
• Resolution: 0.1 mm
• Output: Serial ASCII, pulse train, SDI-12

• Unidata, Australia
• Mod 6541 Precision Water Level Instrument
• Based on float system; as the water level changes the input shaft rotates. An optical encoder is mounted on the input shaft.
• Measurement range: 0 - 65.5 m, or 0 - 13.1 m
• Resolution: 1.0 mm, 0.2mm, 0.1 ft (depending on float pulley used)
• Accuracy: Same as resolution
• Output: "High speed serial signal UNIDATA HSIO standard". Options for SDI-12, 4-20 mA and dual HSIO channels.
• Power: Internal battery pack, 1 year. Or external battery.
  Mod 6541 Precision Water Level Instrument (as above), including Micrologger
  Mod 6542 Water Depth and Temperature Probe
• Based on differential pressure sensor, with venting tube to air. Also measures water temperature.
• Operating range: 1, 2, 5, 10, 20 metres of water
• Resolution: 0.05%, 0.05 mm @ 1 m range
• Accuracy: +/- 0.2% full scale digital output (depth), +/- 0.3% full scale analog output
• Power: 6 - 18 Vdv, 6 mA
  Mod. 6521 Capacitive Water Depth Probe
• Range: Three models, 0 - 0.5 m, 0 - 1.0 m, 0 - 2.0 m
• Accuracy: 0.5 % of full scale reading
• Output signal: 0 - 2.55 Vdc full scale
• Power: 5 Vdc, 3.5 mA

• http://www.stevenswater.com/
• Their water level web page provide a description of sensor principles used: Pressure, Encoders/floats, Non-contact (ultrasonic), Capacitive. They have a broad range of sensors.

Specifications:

• Measurement range: 5 - 50 cm water

Design

• Underground water level monitoring using a hydrobaric sensor
  Sensor is a differential pressure type.

UNIT CONVERSIONS

• Source: Elfa.se
• 1 PSI = 70.31 cm H₂O = 6.895 kPa
• 1 cm H₂O = 0,01422 PSI = 0.09806 kPa
• 1 kPa = 0.1450 PSI = 10.20 cm H₂O

SENSORS

• Pressure sensor #1
  • Supplier: Farnell www.farnell.com, p/n: 731638
  • Mfr: HONEYWELL p/n: 24PCAFA6D.
  • Differential.
  • Pressure range, operating: 0 to 1 psid
  • Sensor needs constant current supply to achieve temperature compensation. References:
  • Signal Conditioning for IC Pressure Sensors.
  • Understanding constant voltage and constant current excitation for pressure sensors
  • Temperature Compensation IC Pressure Sensors
  • Pressure Transducer Basics: A Primer
  • CONCLUSION: Do not use this sensor: Too many problems related to bridge temperature dependency and constant current exitation circuit.
• Pressure sensor #2:
  • Supplier: ELFA, http://www.elfa.se p/n: 73-404-09
  • Mfr: HONEYWELL, p/n: DC030NDC4
  • Differential
  • Pressure range: ±30.0" (76.2 cm) H₂O
  • Sensitivity: 0.133 V/inch H₂O = 52.4 mV / cm H₂O
  • Temperature compensated, amplified bridge output
  • Pressure port dia.: 4.8 mm
• Pressure bladder:
  • Valve dia. (metal threading): 7.7 mm
  • Valve dia (neck): 8.1 mm

ITAS WATER LEVEL SENSOR

• Supplier: ITAS
• Model: MT_3
• Range:
  • Price: NOK 3700