RETIRED ›
This product is no longer available and has been replaced by: CLARIVUE10. Some accessories, replacement parts, or services may still be available.
OBS501 Smart Turbidity Meter with Antifouling Features
Services Available
Repair Yes
Calibration Yes

Overview

The OBS501 is a submersible turbidity probe with active antifouling capabilities for better measurements in biologically active water with both high and low turbidity. It outputs an SDI-12, digitally processed signal that many of our data loggers can measure. The OBS501 is similar to the OBS500, but the OBS501 has better mechanical performance in heavy sediment/sand conditions.


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Benefits and Features

  • Dual backscatter and sidescatter sensors used to measure turbidity
  • ClearSensor antifouling method for better measurements in biologically active water
  • Shutter/wiper mechanism keeps lenses clean
  • Refillable biocide chamber prevents fouling
  • Disposable plastic sleeve facilitates cleanup
  • Optional copper sleeve for additional protection (especially for sea water) or disposable plastic sleeve facilitates easy cleanup

Images

OBS501 in closed shutter position
OBS501 in closed shutter position
OBS501 in closed shutter position
OBS501 in open and closed shutter positions
OBS501 in open shutter position
OBS501 in closed shutter position with cable
Two sleeve options are offered. The three photographs show the plastic sleeve being removed.
Biological fouling on a closed sensor (far left) and an opened sensor after 86 days of deployment in the Atlantic Ocean.

Detailed Description

Design features of the OBS501 include the combination of a backscatter sensor (better at measuring higher turbidity) with a second sidescatter sensor (better at measuring lower turbidity). It has a shutter that is opened only during measurements, which reduces the time that algae or other organisms can cling to its optics.

The OBS501 is constructed to prevent sand grains or packed sediment from getting wedged between the shutter and sensor body, which inhibits the shutter’s movement. To do this, the OBS501's shutter and body were designed to eliminate parallel surfaces between moving parts wherever possible. The probe also uses a flushing action that moves the sediment down and out of the cavity behind the shutter.

To prevent biofouling and ensure better measurements, the OBS501 incorporates the ClearSensor Method  (U.S. Patent No. 8,429,952. This method uses a shutter/wiper mechanism to protect and clean the optics. With the ClearSensor method, a chamber is also filled with a biocide that continuously leaches out over the optics while the probe shutter is in the closed position. ClearSensor® and OBS® are registered trademarks of Campbell Scientific.

The OBS501 can sense if the shutter’s motor is working harder than normal. If it is, the shutter moves slightly back and forth to dislodge sand grains before fully opening or closing.

Campbell Scientific offers a disposable, plastic sleeve that can make cleanup a snap, as well as a copper sleeve that can provide additional protection, especially in sea water.

Specifications

Dual Probe 90° sidescatter and backscatter
Measurement Range 0 to 4000 NTU
Active and Passive Antifouling Shutter, wiper, biocide, copper, optional removable sleeve
Accuracy ±2% of reading or 0.5 NTU (whichever is greater)
Operating Temperature Range 0° to 40°C
Storage Temperature Range 0° to 40°C
Temperature Accuracy ±0.3°C
Emitter Wavelength 850 nm
Power Requirements 9.6 to 18 Vdc
Measurement Time < 10 s
Maximum Submersion Depth 100 m (330 ft)
Diameter 4.8 cm (1.88 in.)
Maximum Cable Length
  • 116 m (380 ft) for 1 channel SDI-12 or analog
  • 15 m (50 ft) for RS-232
Length 27 cm (10.63 in.)
Weight 0.59 kg (1.30 lb)

Power Consumption
Quiescent < 200 µA
Measurement < 40 mA
Communication < 40 mA
Active Shutter Motor < 380 mA

Outputs
SDI-12 Version 1.3, 1200 bps
RS-232 9600 bps, 8 data bits, 1 stop bit, no parity, no flow control
Analog 0 to 5 Vdc

Compatibility

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Dataloggers

Product Compatible Note
21X (retired)
CR10 (retired)
CR1000 (retired)
CR1000X
CR10X (retired)
CR200X (retired)
CR211X (retired)
CR216X (retired)
CR23X (retired)
CR300
CR3000 (retired)
CR310
CR500 (retired)
CR5000 (retired)
CR510 (retired)
CR6
CR800 (retired)
CR850 (retired)
CR850 (retired)
CR9000 (retired)
CR9000X (retired)

Frequently Asked Questions

Number of FAQs related to OBS501: 1

  1. What are the differences between the different turbidity units used, such as NTU, FBU, FTU, and FNU?

    It used to be that NTUs were the unit for all turbidity sensors. In 2007, an ASTM committee formed and established different units for each category of turbidity sensor technology, and there are many. Backscatter sensors such as the OBS-3+ and the OBS501 have units of FBU (Formazin Backscatter Units), whereas ISO 7027 side-scatter sensors have units of FNU (Formazin Nephelometric Units). The side-scatter OBS501 and the ClariVue™ sensors are part of this category. While sensors of different technical designs can be calibrated and measure Formazin the same, they will not make the same measurement in natural waters where size, shape, color, reflectivity, etc., of the particles vary. The ClariVue™ sensor measurements will not match the OBS-3+ measurements in natural waters.

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