Monday, August 13, 2012

Calibrating the MOCNESS Flow Meter

The Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) is a mainstay in the plankton sampling on this Ocean Acidification cruise.  The system carries nine nets that are triggered via a shipboard computer, allowing us to sample different depth layers in the ocean. The system also carries a suite of environmental sensors that measure pressure (from which we calculate depth), temperature, conductivity (from which we calculate salinity), frame angle, and water flow past the net.  The frame angle and water flow are used to calculate the volume of water filtered by each sequentially opened net. The flow meter is mechanical and has a propeller driving a gear shaft that rotates a cylinder with an embedded magnet that moves past an underwater reed switch. With each 360 degrees the magnet passes by the switch causing it to close for a moment, which is recorded as a flow count.  Each flow count thus represents a distance traveled by the flow meter. Quantifying this distance requires calibrating the flow meter.

Leo, Gareth, and Alex on the fantail preparing the MOCNESS for the flow meter calibration (Photo: P. Wiebe)

On each cruise, calibrating the flow meter is done by deploying MOCNESS to a shallow depth and then towing it horizontally back and forth on a trackline over a prescribed distance. We did this on 11 August at our test station.  To calibrate the flow meter, we towed the MOCNESS at a depth of approximately 50 m for a distance of about one half a nautical mile from southeast to northwest (a course of 340 degrees) and then in the reverse direction (160 degrees) the same distance in order to eliminate any effect of differential current flow on the calibration.

Map showing the MOCNESS flow meter calibration runs

During the tow, the MOCNESS software logged the data coming from the underwater unit and the GPS latitude and longitude positions. The bridge called down start and end marks for each half-mile segment and the MOCNESS operator wrote down the flow count number at each of the marks.  We then used a custom Matlab program to compute the distance for each run and to make a plot of the tow segments superimposed on the total tow.  The calibration coefficient determined on this cruise ended up indicating that the flowmeter moves a distance of 6.3425 m during each count, a number that closely matches the coefficients determined on two earlier cruises. We will use the average of the three calibrations as the calibration coefficient for the MOCNESS tows taken on this cruise.

Peter Wiebe

12 comments:

  1. The Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) is a mainstay in the plankton sampling on this Ocean Acidification cruise. PT878 portable liquid flowmeter

    ReplyDelete
  2. The oil flow meters are generally used for measuring the consumption of heating oil. You may buy the best oil meters at the affordable prices by visiting at http://www.anglonordic.co.uk/installation-equipment/oil-flow-meters.html

    ReplyDelete
  3. Starting with the simplest equipments used in general laboratories, medical institutions, and university and school labs. The range of such instruments includes laboratory incubator which is highly in demand from medical institutions and more, then comes laboratory ball mill which is designed for mixing and grinding purposes in industries such as cement industries, paints, etc., and afterwards there is laboratory water bath used by medical labs, nursing homes and research institutions, shaking machine, deep freezer, heating mantle, distillation apparatus, universal oven, vacuum oven, ultrasonic cleaner bath, muffle furnace, vertical autoclave, high vacuum pump, sieve shaker, and turbidity meter which are used extensively by scientists in many developments. The range of laboratory instruments used should be made using premium grade raw materials which offer high strength and durability to the products.


    Stream Flowmeter

    ReplyDelete
  4. We are offering an amazing range of awesome quality universal water current meter & Automatic Weather Station to our valuable client.water current meter is used to determine current flow velocities in main water courses, Universal Water Level Recorder are manufactured by high quality.

    ReplyDelete
  5. Water Current Meter Level Recorder developed by KaizenImperial is based on New Technology, essentially to monitor, measure and record fluctuations in water level of ground water as well as surface water.

    ReplyDelete
  6. Thanks for posting the useful information.
    Manas Microsystems Pvt. Ltd. is one of the India’s best leading manufacturing of Electromagnetic Flow Meters, Water flow meter, Digital flow meter, Gas and Steam Flow Metering Systems & other related process instruments in India. We provide best gas flow meter, magnetic flow meter, water flow meter, electromagnetic flow meter, ultrasonic flow meter, digital gas flow meter, industrial flow meter and portable water flow meter from Pune, Maharashtra, India. Call Manas Microsystems Pvt. Ltd. to request a quote.
    magnetic flow meter - Manasmicro
    Electromagnetic flow meter
    ultrasonic flow meter – Manasmicro
    gas flow meter - Manasmicro

    ReplyDelete

  7. Thanks for sharing this Article. Here is some information about Intermittent Water Meters.

    ReplyDelete
  8. Thanks for sharing about MOCNESS flow meter. We are also one of the leading manufacturers of flow meter and level transmitter serving across 100+ countries around 20+ years.

    ReplyDelete
  9. Manufactures of Automatic water level controller and Indicator in Chennai and Tamilnadu, wireless water tank level indicator and wireless water level controller in Chennai, OMR, Anna Nagar, Velachery

    ReplyDelete
  10. Your blog is very good .. I am very happy after reading your blog and I got a lot of information from your blog which is of my use. And I hope that you will bring such good blogs ahead Electromagnetic Flow Meter

    ReplyDelete