Bronkhorst FLOW-BUS interface Manual do Utilizador descarregar pdf (Página 17)

BRONKHORST®



2.5 POWERSUPPLY

BronkhorstusesFLOW‐BUScableswithextrawiresinsidefor+15…24Vdcand0Vdcinordertohandlepowersupply

and communication within the same cable. Because RS485‐cabling needs a daisy‐chain connectionand power‐lines

preferastar‐pointconnection,wecametoacompromiseofbothintheFLOW‐BU

Scabling.Bronkhorstcanadviseyou

how to power your FLOW‐BUS system. It is the best to keep the power‐lines as short as possible, so local power‐

supplyispreferred.Thisofcourse,dependsonyourdemandsofbuilding‐upyoursystem.

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Page17

FLOW‐BUSinterface9.17.024

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Themaximumnumbersofinstrumentsononepowersupplydependsofseveralparameters.

1. Minimumvoltageontheinstrument(+15V‐10%=13.5V).

2. Powersupplytolerance

3. Maximumcontactratingoftheconnectors.

4. Voltagedropacrosscables.

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RJ45cablesystemsusetwointernalwiresforpowersupply,M12cablesystemsonlyone.

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

ρR 

Wireresistanceca

nbedonemanuallybythefollowingformula:



Where“l”isthelengthoftheconductor,measuredinmeters[m],“A”isthecross‐sectionalareaoftheconductor

measuredinsquaremeters[m²],and“ρ”(r

ho)istheelectricalresistivity(also calledspecificelectricalresistance)of

thematerial,measuredinohm‐metres(Ωm)



Asanexample:



Wirediameter1mm

0.0223Ω

0.001π0.25

81.75eR 





Wirelength1m

Coppersp

ecificelectricalresistance

=1.75E‐8m

=3.14

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Calculationofwireresistanceandmaximumwirecurrentcanalsobedoneon:

http://circuitcalculator.com/

wordpress/2007/09/20/wire‐parameter‐calculator/

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Usingstandardpower‐suppliesfromBronkhorstandShieldedTwistedPairpatch‐cablewithRJ45

connectorsfornonIP65applicationsandDeviceNetcableswithcircularM12connectorsforIP65

applications:

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Aclusterof4digitalcontrollerscanbepoweredlocallyfroma distanceapprox.<=6.5metersfromthe

power‐supply.



Poweringmo

reinstrumentswillreducethedistanceallowedtothesupply‐unitinlinearrelationship.

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