Bronkhorst FLOW-BUS interface Uživatelský manuál Strana 17

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BRONKHORST®
2.5 POWERSUPPLY
BronkhorstusesFLOWBUScableswithextrawiresinsidefor+15…24Vdcand0Vdcinordertohandlepowersupply
and communication within the same cable. Because RS485cabling needs a daisychain connectionand powerlines
preferastarpointconnection,wecametoacompromiseofbothintheFLOWBU
Scabling.Bronkhorstcanadviseyou
how to power your FLOWBUS system. It is the best to keep the powerlines as short as possible, so local power
supplyispreferred.Thisofcourse,dependsonyourdemandsofbuildingupyoursystem.
Page17
FLOWBUSinterface9.17.024
Themaximumnumbersofinstrumentsononepowersupplydependsofseveralparameters.
1. Minimumvoltageontheinstrument(+15V‐10%=13.5V).
2. Powersupplytolerance
3. Maximumcontactratingoftheconnectors.
4. Voltagedropacrosscables.
RJ45cablesystemsusetwointernalwiresforpowersupply,M12cablesystemsonlyone.

Ω
A
l
ρR
Wireresistanceca
nbedonemanuallybythefollowingformula:
Where“l”isthelengthoftheconductor,measuredinmeters[m],“A”isthecrosssectionalareaoftheconductor
measuredinsquaremeters[m²],andρ(r
ho)istheelectricalresistivity(also calledspecificelectricalresistance)of
thematerial,measuredinohmmetres(Ωm)
Asanexample:
Wirediameter1mm
0.0223Ω
2
0.001π0.25
1
81.75eR
Wirelength1m
Coppersp
ecificelectricalresistance
=1.75E8m
=3.14
Calculationofwireresistanceandmaximumwirecurrentcanalsobedoneon:
http://circuitcalculator.com/
wordpress/2007/09/20/wireparametercalculator/
UsingstandardpowersuppliesfromBronkhorstandShieldedTwistedPairpatchcablewithRJ45
connectorsfornonIP65applicationsandDeviceNetcableswithcircularM12connectorsforIP65
applications:
Aclusterof4digitalcontrollerscanbepoweredlocallyfroma distanceapprox.<=6.5metersfromthe
powersupply.
Poweringmo
reinstrumentswillreducethedistanceallowedtothesupplyunitinlinearrelationship.
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