Bronkhorst RS232 interface Manual do Utilizador descarregar pdf (Página 27)

BRONKHORST®

Page27RS232interface    9.17.027

4 DUALINTERFACEOPERATION



Whenoperatingacontroller(readingmeasuredvalueandsendingsetpoint)forproperoperationitisimportantthat 

thecontroller getsits setpoint fromtheright source.Setpointsmaycomefromdifferentsources:analog input, field

businterfaceorRS232ormaybeoverruledbyclosevalveoropenvalve(purge)

commands.Thereforeitisimportant

toknowwhatthesetpointsourceofthecontrolleris.Thiscanbesetbymeansofparametercontrolmode(process1,

parameter4).



Insomecasesitispossiblethatthesetpointsmaycomefrom2sourcesatthesametime.Thelastsend

setpointwill

bevalidandsendtothecontroller.Thisisthecaseincontrolmode=0,whensetpointsmaycomethroughanyfield

businterfaceorRS232.



However,there could be situations where control over the instrument seems impossible. This is the case when the

instrument comes into a

 safe‐state e.g. when field bus communication is disturbed or disconnected. Valve will be

forcedtoasafestateautomatically:closed(NC)orfullyopen(NO).



IncaseyouwanttogetcontrolbackviaRS232operation,youhavetochangethecontrolmode.Whencontrolmode

getsvalue18,

safestatewillbeoverruledandsendingsetpointsviaRS232interfacewillhaveeffectonthecontroller

again.



Seealsodocumentnr.9.17.023formoredetaileddescriptionaboutdigitalinstrumentparametersand

theirbehaviour.

http://www.bronkhorst.com/en/downloads/instruction_manuals/

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Bronkhorst RS232 interface Manual do Utilizador Página 27