Campbell-scientific CR800 and CR850 Measurement and Control Systems Uživatelský manuál stáhnout pdf (Strana 442)

Section 11. Glossary

442

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(86,400seconds),itissynchronizedwiththe24‐hourclock,sothatthe

programisexecutedatmidnightandeveryScan()Intervalthereafter.

Theprogramisexecutedforthefirsttimeatthefirstoccurrenceofthe

Scan()Intervalaftercompilation.IftheScan()Intervaldoesnotdivide

evenlyinto24hours,executionwillstartonthefirstevensecondafter

compilation.

scantime

WhentimefunctionsareruninsidetheScan()/NextScanconstruct,

timestampsarebasedonwhenthescanwasstartedaccordingtothe

CR800clock.Resolutionofscantimeisequaltothelengthofthescan.

Seesystemtime

(p.445).

SDI‐12

SerialDataInterfaceat1200bps.Communicationprotocolfor

transferringdatabetweendatarecordersandsensors.

SDM

Synchronousdeviceformeasurement.Aprocessor‐basedperipheral

deviceorsensorthatcommunicateswiththeCR800viahardwireovera

shortdistanceusingaproprietaryprotocol.

SeebeckEffect

Inducesmicro‐Voltlevelthermalelectromotiveforces(EMF)across

junctionsofdissimilarmetalsinthepresenceoftemperaturegradients.

Thisistheprinciplebehindthermocoupletemperaturemeasurement.It

alsocausessmall,correctablevoltageoffsetsinCR800measurement

circuitry.

Semaphore(MeasurementSemaphore)

Insequentialmode,whenthemainscanexecutes,itlockstheresources

associatedwithmeasurements,i.e.,itacquiresthemeasurement

semaphore.Thisisatthescanlevel,soallsubscanswithinthescan

(whethertheymakemeasurementsornot),willlockoutmeasurements

fromslowsequences(includingthesy

stembackgroundcalibration).

Lockingmeasurementresourcesatthescanlevelgivesnon‐interrupted

measurementexecutionofthemainscan.

Send

TheSendbuttonindataloggersupportsoftware

(p.76).TheSend

commandsendsaCRBasicprogram,oranoperatingsystem,toaCR800.

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Campbell-scientific CR800 and CR850 Measurement and Control Systems Uživatelský manuál Strana 442