DE1798188C3 - Circuit arrangement for measuring the flow velocity and the flow rate of flowing media - Google Patents

Description

th and lying in the medium flow

other Dia.unalpunkt the bridge “Um. and that The vision consists of the one icile etes adjustable resistance (/>,) at which em,

f'l ■ Sn innunc (f) anliegi. as well as from a dnt- «n'ÄrSmuä linden NTC thermistor (ΛΤΓ,) with adjustable resistance S! ' u d another W.derstand (P ₄ ). to the McBspunnung ^) wrd.

p 15 Purposes hereks to the smallest Sirömungsgesdnv, nd> g- ^ u. a, _{bcsondeni for me} dizm. see

emem I.

Lowest Sirömungsgesdn, ndg, _{bcsondeni for me} dizm. see ^ _the flow essentials under 1 ins i,, e is the way ^ u independent. full clektroniwiener the medmmschen

The ErHndunu refers to a formwork arrangement for measuring the flow velocity-riding and the flow rate of flowing media with two connected in a bridge and, m Med.umstrom Hanging thermistors.

^25th

³ °

MEASURING ACCURACY TIGHT. _nLr ^

S iXile change ^ according to the hot wire, Flow meter. the following

^{D | C Lrlmi} S ^1S de 'Look at the drawing

_Zeldinung Hegen terminals 1, 2 is connected _to terminal 1 ng a _Leilu 4 with EMEM resistance _is further connected via a line 5

all other possible flow rates The measured values differ in impermissible W ^ isc of the current mentioned for the aforementioned speed made temperature compensation away. The temperature compensation w, d Iu of the known device is achieved in that A third resistor is used for the bridge circuit - is considerably more oil than a first resistance and is a vitr ^ r resistance considerably greater than a / continued resistance is. As a result, the current flow ίη should be independent of the resistors, the hot wires from the temperature of the flowing med. to possible «remain constant. However, the higher that

the measuring voltage, whereby the relative error of the device for the other possible currents velocities is greater; see TabeH page 24 of the ^^ i ^ "^^ / '^^ ^ _β , _εί1ΰΓ ^ ₇ C _{1 flows} past.

ai dun H «' _{changed as0} display

bm SpaaW ^ _{at when} standing still

gn bL ^ ^the _{iron temperature} change to ver-medium un bridge branch from a

mtidtn. κ f ^ _{d a} second hot

two en W, dtnjand1 ^ _{8 e} . _{nste] Ibar resistance P}

^leIlLryv ; ^ - """ _ile resistance Rv. is provided on the one hand» ^ De, jw «^^ _{on the other hand} via a m German W _{two NTC} thermistor NIC ₂ .

J ^ J ^^ _hinaU s with the line 7 ver-Lemerer ^ t _{zwdtM NTC} thermistor WrC is

bound. Pa _WlderstandP , by means of Le, t _U ngen9,

^ _t ^ ^^ _Abgnff

st ^ ^ over a _resis tandesP _t connected

g * th _adjustable resistance P. cherishes with

«SS at both ends via cable and 13

is readable. The tMnsai / .mugmiin.i.iK- »· vw

Hot-wire flow meters therefore only start at Flow velocities greater than 1 m / s.

The object of the present invention is to provide a flowmeter of the type mentioned for liquids and / o ^r gases. which shows even at the lowest flow speeds, i.e. less than 1 in ν, practically independent of the respective temperature of the flowing medium.

can be selected so that the residual voltage occurring between the line 5 and the end 23 of the second adjustable resistor F., can be adjusted to zero.

Via the line 13, there is also a chip closure at the end of the second adjustable resistor P. the third adjustable resistor P _{3 from the components}

and fourth adjustable resistor P ₁ . One end of the third NTC ₃ thermistor is connected to the line 13; its other end is connected via a line 14 to one end of the fourth adjustable resistor / ^. At its other end K; this resistor 1 \ is connected to the line 5 via a line 15. Parallel to the third thermistor ATC. Is the third adjustable resistor P ₃ , one end of which is connected to one end of the third thermistor NTC ₆ and the tap of which is connected to the other end of the thermistor NTC ₃ .

Between the line 14 of one end of the resistor P ₄ and the line 15 of the other, a voltage will be tapped which is proportional to the flow velocity or the amount of the medium flowing past the thermistors NTC ₁ , NTC, and ATC. This voltage is temperature-compensated in the aforementioned manner.

If, as shown in the illustrated exemplary embodiment, the resistor P _{i is designed} as an adjustable resistor, the mentioned compensated voltage can be tapped adjustable between its tap 24 and its end connected to the line 15. The value to be set depends on the input values of the downstream measuring devices.

According to the drawing, the compensated measurement voltage is supplied via lines 16, 17 from tap 24 or the line 15 is supplied to a measuring device.

It is advisable to use the three thermistors ATC ₁ , NTC, _and ntc, _{m C} i " _em

to be arranged differently. This is kept laminar.

öriich. in particular

knife several of the al »" ", erscliied-

inaccessible. On this Wu *. * - «""" _Q borrowed Slromongsveneilungen in the 'big «, Uucr

aaSfiS

the third placed in the flow

ches temperature compensated

1 sheet of drawings

Claims (1)

Circuit expansion for measuring the S.rö ty vufoabc is ingenious, the invention thereby This Autgatx. lh. e-NTC thermistor an ei.v solution that parallel to the u-n Adjustable contradiction S- ^ ^ _{n Dia} , _onal . Pick up a series ^ «- ^ ^