Glossar
2 way actuators
2 way actuators are discontinuous actuators with only 2 positions (on/off). There are only 2 values which appear subject to a continuous actuating variable. Relay's, limit signal indicator and level switches give such a binary signal.
2 way actuators are often used to regulate temperatures, for example in smoothing irons or in electric kettles.
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In contact the bimetal actuator closes the power circuit, which heatens up the heating winding. If the temperature rises over the given set value, the bimetal stripe bends upwards because of the different coefficients of linear thermal expansion of the two metals. The contact is then disconnected and the heating coil is able to cool down. The cooling heating coil also relaxes the bimetal that unbends to its original position and the contact is made again. |
Important advantages of 2 way actuators are:
Reliability, simple assembly, low costs. Disadvantages are: commuting control variable, that generates a jumping operation. 2 way actuators are especially used in heating and cooling systems, for regulating the liquid level, the pressure and revolution speed.
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Prospektiv GmbH, Dortmund 2008, Germany