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OTT PLS 500 - Pressure Level Sensor

Robust ceramic pressure transducer for water level measurement

Building on years of experience with the robust and accurate OTT PLS, the PLS 500 water level monitoring solution adds innovative metadata and internal sensors to remotely verify device performance providing peace of mind for long term deployment. 

  • Surface water, Groundwater
  • Vented pressure cell
  • Water Level, Pressure, Temperature, Position of Sensor, Internal Relative Humidity
  • Water level and temperature measurement - for use with external data logger
  • 0 … 10, 20, 40, and 100 m
  • ± 0.05% full scale (linearity and hysteresis) // Meets USGS OSW
  • No
  • SDI-12 and RS485 (SDI-12 v1.4 and Modbus RTU)
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The OTT PLS 500 measures water level, depth to water, or pressure by means of an easy to maintain, ceramic pressure cell. This highly accurate sensor includes design features such as four internal compensations, stainless steel housing, and a rugged cable making it ideal for monitoring water level in a variety of applications. Common communication protocols (SDI-12 and Modbus RTU) allow for seamless integration with external data loggers. The accurate temperature measurements and built-in microcontroller compensate for environmental changes in water density. Built-in QA/QC and metadata along with reduced sensor drift allow you to have full confidence in your long-term data.

  • Automatic Compensations​: Automatically compensate for changes in atmospheric pressure with the vented probe. Reduce the amount of equipment needed in field by forgoing additional barometric pressure sensors and achieve better accuracy with a single compensated sensor.

  • Custom Cable: All PLS 500s are manufactured with cables cut to the users specifications upon order. Please specify the length of cable (meters or feet) that you require with any quoted item 

  • Position Sensor: Remotely monitor probe movement in the field with an internal inclinometer, enabling warnings if sensor position has changed due to in-stream events via automatic status flags or direct measurement. 

  • Internal Humidity Sensor:​ The integrated internal humidity sensor outputs automatic status flags or direct humidity measurements to help you understand if condensation may have formed, impacting your pressure measurements. 

  • Data Processing:​ Internally convert high frequency (4 Hz) measurements to calculations such as computed averages, minimum/maximum levels, and instantaneous values over user defined intervals, enabling greater information reporting and eliminating manual data post-processing/analysis. 

  • Discharge Calculations​: Automatically calculate discharge from either a user defined rating table or ISO 1100-2 exponential formula set-up via SDI-12 commands. Minimize the need for data post-processing by directly outputting discharge from a trusted level sensor. 

  • Rugged Design: Ceramic pressure cell resistant to physical force and enclosure made of high-quality, saltwater resistant 904L stainless steel for use in coastal environments. The robust ceramic pressure cell offers industry-leading accuracy and does not deform over time like membrane technology, providing long-term measurement stability.

Measuring water level in surface and groundwater, including:
 

  • Stations with sloping bottom, e.g. water banks
  • Small diameter pipes or holes (from 1" Ø)
  • Dams, weirs, irrigation systems
  • Waterways that occasionally ice over
  • Brackish water, saltwater
  • Flood warning
  • Waterways that do not contain water throughout the year (e.g. retaining basins)
Brochure - OTT PLS 500 - EN
Brochure - OTT Water level measurement
Data Sheet - OTT PLS 500 - EN
Declaration of Conformity - OTT PLS 500 - EN
Declaration of Conformity - OTT PLS 500 - EN1
Leaflet - Pressure Probe OTT PLS
Operating instructions Pressure Probe OTT PLS
Operating instructions Pressure Probe OTT PLS 500 - EN
OTT PLS - CE Konformitätserklärung | Declaration of Conformity | Declaration de Conformité
OTT PLS 500 vs OTT PLS - EN
Product Guide - OTT PLS 500 - EN
Supplement to operating instructions Pressure Probe OTT PLS – Plug-in pressure probe cable
Technical Note - Sensor Selection Guide Groundwater
Technical Note - Sensor Selection Guide Surface Water
White Paper - OTT ecoLog Guidance: Remote communication via mobile networks
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WATER LEVEL (PRESSURE)
Measurement Range 0 ... 10 m, 20 m, 40 m, 100 m / 0 ... 33 ft, 66ft, 131 ft, 328 ft
Accuracy (linearity and hysteresis) ±0.05 % full scale
Accuracy (linearity and hysteresis) USGS OSW 0 ... 10m / 0 ... 1 bar variant ±2 mm / 0 ... 5 m (-5 … +55 °C)
±3 mm / 0 ... 5 m (-20 … -5 °C; +55 … +70 °C)
±5 mm / 5 ... 10 m (-20 … +70 °C)

0.007 ft / 0 ... 17 ft (+23 … +131 °F)
0.010 ft / 0 ... 17 ft (-4 … +23 °F; +131 … +158 °F)
0.017 ft / 17 ... 33 ft (-4 … +158 °F)
Long-term stability (linearity and hysteresis) ± 0.1%/full scale
Units m, cm, mm, bar, mbar, kPa

ft, inch, psi
Pressure Sensor Ceramic / temperature compensated
Resolution 0.001 m / 0.1 cm / 0.00001 bar / 0.01 mbar

0.001 ft / 0.001 in / 0.00001 psi
Temperature-compensated operating range  -20 °C (ice-free) ... +70 °C / -4 °F (ice-free) ... +158 °F
TEMPERATURE
Measuring Range  -40 °C ... +70 °C / -40 °F ... +158 °F
Resolution 0.01 °C / 0.01 °F
Accuracy ±0.15 °C (Typ. ± 0.05 °C) / ±0.07 °F (Typ. ± 0.03 °F)
Units °C / °F
INTERNAL RELATIVE HUMIDITY
Measuring Range 0 ... 100% RH (non-condensing)
Resolution 1% RH
Accuracy ± 3% (0 ... 100% RH)
Typically ± 2% (10 ... 80% RH)
Units % RH
COMMUNICATION
Physical interfaces SDI-12 and RS-485
R5-485 protocols SDI-12 (V1.4), Modbus RTU
POWER
Supply voltage 5.5 ... 28.8 V, typically 12/24 V DC
Power consumption - sleep < 250 µA; typically 15 µA
Power consumption - active < 4mA; typically 2.9 mA
MEASUREMENT
Measured Values - Water level/water pressure
- Internal Relative Humidity
- Water temperature
- Position of sensor
Value Processing - Average pressure or level over measurement interval
- Minimum pressure or level over measurement interval
- Maximum pressure or level over measurement interval
- Median pressure or level over measurement interval
- Standard deviation of pressure over measurement interval
Derived Parameters Discharge
Measurement Interval 0.5 s ... 59.5 s (1.5 s default)
ENVIRONMENTAL
Temperature range, operating -20 °C (ice-free) ... +70 °C / -4 °F (ice-free) ... +158 °F
Temperature range, storage -40 °C ... +80 °C / -40 °F ... +176 °F
Humidity 0% ... 100%
IP rating (probe) IP68
DIMENSIONS/WEIGHT
Pressure probe LxD: 194x22 mm / LxD: 7.7 x 0.9 in
Cable length 2 ... 200 m, ± 1% / ± 5 cm // 7 ... 656 ft, ± 1% / ± 0.17 ft

*Longer cable lengths available upon request.
Pressure probe ~650 g / ~22.9 oz
Pressure probe cable ~ 55 g/m // ~0.51 oz/ft
MATERIAL
Pressure probe housing POM, Stainless steel 1.4539 (904L); resistant to sea water
Membrane AI203 ceramics
Cable jacket PUR (UV resistant)
REGULATORY
FCC FCC/ICES Suppliers Declaration of Conformity (SDoC) FCC Part 15 Rules Section §15.109
CE IEC61326-1:2013
DIN EN ISO 4373 Measurement reliability / performance class 1
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