水产监测和控制

Campbell Scientific systems monitorand control a Mississippi catfish farm
Making success in aquaculture automatic

Successful aquaculture ultimately hinges on concentrations ofdissolved oxygen.  Measurement of DO is the single mostimportant water quality parameter.  It is also the reason manyaquaculturists are forced to make several pond checksnightly.  Without close, continuous monitoring, the necessarywarnings that help avoid fish stress and mortality might goundetected—causing an entire production cycle to go belly up.

An automated aerator restores dissolved oxygenlevels on one of many ponds at the Lee Catfish Farm inMississippi.  In addition to water conditions, current drawnby the aerator can also be monitored.

That’s why, in May of 1996,LeviLee and his son Jeff, turned toCampbell Scientific for help.  They purchased a CR10Measurement and Control System for use on their multiple-pondcatfish farm in Macon, Mississippi.  Knowing all too well thedemands several pond checks a night make on individuals, as well asentire aquaculture operations, the Lees no ware able to check andcontrol their ponds making only one stop: at their personalcomputer.  And, if critically low dissolved oxygen conditionsshould occur—in any of their ponds—a radio-controlled alarm alertsthe Lees through the same computer, saving them precious time andsleep.  It also allows them to take fast, informed,restorative action.

The intitial installation consists of two stations, bothfeaturing a CR10(X) datalogger for measurement and controldecisions, an SDM-CD16AC for controlling AC power to aerators, andEF Johnson radios for wireless telemetry.  The first stationmeasures an OxyGuard DO probe in each of four ponds and watertemperature in one of those ponds using a CSI 107-L sensor. Thesecond station monitors dissolved oxygen in five ponds, again usingOxyGuard DO probes.

Though pond-condition data can be viewed andcontrolled via a personal computer, special display-equippedenclosures (shown open above) also make data visible on-site.

Both of the stations are housed in12" x 14" fiberglassenclosures equipped with a special two-line,40-character LEDdisplay that allows dissolved oxygen conditions to be viewed at thesite.  In addition to monitoring, the dataloggers areprogrammed to control paddle-wheel aerators, set in motion toremedy low pond oxygen.  Alarm conditions are triggered whenDO dips below user-determined levels, sending a warning sound backto the operator.

The CR10(X)s are equipped with the MODBUS Operating System todrive the two stations, allowing data to be continuously monitoredfrom the base computer running In Touch software.  The Leesare afforded additional control through useful, intensive graphicsmade possible by In Touch.

The dataloggers communicate with the computer using convenient,wireless RF telemetry.  (Editor’s note: Also popular are phonecalls made to a pager or voice-synthesized calls received at homeor office.)

Pleased with the many advantages the initial system offered, theLees augmented their operations by adding and instrumenting twoponds in 1999.  In addition, they installed yet anotherCR10X,thistime adding electrical current monitoring. Now the Leescan monitor the amperage drawn from the paddle wheel motors; if toohigh, they know a motor needs to be shut down and serviced.

With the upgrade to their monitoring and control system, theLees also took the opportunity to modify datalogger programming andcan now create different alarm and control set points for morningand evening operation (knowing that aquatic-plant life becomesoxygen-consuming rather than oxygen-producing during darkness, sothat a low-oxygen event just after sunset is far more critical thanone just before sunrise).

An additional benefit is that theCR10(X)s allow data to becollected overextended periods, painting a useful picture of pondconditions over time.  That, inturn, leads to better pondmanagement.