Bronkhorst MASS-VIEW Series Instrukcja Użytkownika Pobierz pdf (Strona 7)



BRONKHORSTHIGH‐TECH



9.17.051 MASS‐VIEW®series Page7

1.8 Sensor principle

The MASS‐VIEW

 operates on the principle of direct thermal mass flow

measurement. The thru‐flow design sensor consists of a heater resistor and a

temperature sensing resistor. Both resistors are made of temperature sensitive

resistivematerialthatiscoveredwithastainlesssteeltube.Thenecessaryheating

power to keep the temperature

difference between the heater resistor and the

sensing resistor at a constant level depends on the mass flow. A different and

unique heater current is produced for each value of the flow. The measurement

principledescribediscalledConstantTemperatureAnemometry(CTA).



Thetransferfunctionbetweenmassflowandoutput

signalcanbedescribedbythe

equation:



signal

 =outputsignal

K

 =constantfactor

 

(includesλ–heatconductivity,C

–specificheat,μ–dynamicviscosityandρ–densityofthegas)





 =massflow

1.9 Needle valve principle

Theneedlevalvehasanorificewithalong,taperedconicalseat.Aneedle‐

shapedplunger,ontheendofascrew,exactlyfitsthisseat.Asthescrew

is turned and the plunger retracted, flow between the seat and the

plungerincreases.Sinceittakesmanyturnsofthefine

‐threadedscrewto

retracttheplunger,preciseregulationoftheflowrateispossible.



1.10 Constant-flow controller principle

Flowcontrolwithaneedlevalveatconstantpressureresultsinaconstant

flowrate.Butwhenpressureconditionschange,theflowwillalsochange.



Withaconstant‐flowcontroller withvaryingupstreampressuretheflow

willalmostbeconstant.



Bykeepingthepressuredropacrossaneedlevalve

constanttheflowratealsoisconstant.Deviationsof

thepressuredroparecompensatedbyamembraneoperatedvalve.Thismembraneisactuatedbya

spring.Thespringforceclosesthevalve.

Theequilibriumbetweenclosing(valvespring)andopening(membrane)keepstheflowconstant.



Schematicflowdiagramconstant‐flowcontroller



msignal







1 2 3 4 5 6 7 8 9 10 11 12 ... 19 20

Komentarze do niniejszej Instrukcji

Brak uwag

Bronkhorst MASS-VIEW Series Instrukcja Użytkownika Strona 7

Komentarze do niniejszej Instrukcji

Powiązane produkty i podręczniki dla Sprzęt komputerowy Bronkhorst MASS-VIEW Series