Text version of the page

General information

Process controllers

Why process controllers with an analogue input? For many measuring operations, a digitalsignal acquisition is too inaccurate or tooexpensive. This is why analogue signal acquisition is often used in industrial envi- ronments. This includes for example tempe- rature, weight (mass), pressure, filling level,volume (flow), speed, acceleration, positionand many others. The sensor signals are mostly very small (in the mV or µV range) The K
ÜBLER process displays linearisethese signals with up to 32 control points,depending on the version.
ÜBLER Process Controllers amplifythese signals, correct possible errors andsend them to the display. The CODIX 850/851 and Type 573,K CODIX 850/851 process measuring transducers convertthese signals into standard signals (e.g. 0 ... 10 V or 4 ... 20 mA). These signals can thenbe processed further and/or displayed. Inaddition it is possible to transmit the stan- dard signals over larger distances. Many sensors do not supply a linear output sig- nal. The K Input signals and output signals K
ÜBLER offers the following input signal ran-ges, according to the version:
ÜBLER offers the following output signal 0 ... 20 mA4 ... 20 mA±20 mA±100 mV, ±10 V0 ... 10 V DC 2 ... 10 V DC 0 ... 4 ranges for further processing: 0 ... 20 mA4 ... 20 mA20 ... 4 mA20 ... 0 mA0 ... 10 V+ 00 Ω 10 V Error behaviour according to NAMUR NE43,optocoupler or relay outputs in conjunctionwith adju 0 ... 4000 Ω PT1000, PT100, Ni100 for 2, 3, and 4 wiretechnologyThermocouples B, E, J, K, N, s stable limit values. R R, S, T The 2 .. 10 V and 4 ... 20 mA signals havethe advantage that they also offer sensormonitoring at the same time. A 0 V or 0 mA signal may for instance mean that the sen- sor line is broken. With the The 4 ... 20 mA and 20 ... 4 mA signals have the advantage that they also offer sensor monitoring at the same time. A 0 mA signalmay for instance mean that the sensor lineis broken. E Example
Measured value/[mA] Pressure/[Pa]Point 1Point 2 A digital display with analogue input, e.g. CODIX 550 can be used to replace or com-plement the pressure gauges on a com- pressor. The current signal of the pressure sensor is displayed as the pressure on the display. Programming of the characteristic curve: Point 1: 4 mA, 2.5 Pa Point 2: 20 mA, 30 PaMinimum and maximum values are saved and can be read at any time. The displayvalue can easily be scaled, to show forexample atmospheres or bar instead of Pa, by modifying the points of the characteri- stic curve. The integration function (totaliser) The devices equipped with the integration function (totaliser) can calculate the inte- gral, that is to say “totalize” the analogue signal, using any period of time.A typical field of application is flow measu-rement. In this case, an analogue sensor measures the flow quantity per time unit in a pipe and displays the momentary flowvalue (e.g. litres per minute). The integrati-on function (totaliser) calculates, from this constantly fluctuating quantity, a “total”,that is to say it defines the absolute quanti-ty that has flowed through the pipe (e.g. in litres).
1/2008 www.kuebler.com 9