Setting the switch points of an electronic pressure switch for a credit card applicatoin in the vacuum range isn’t a self-explanatory task. The following article therefore explains what must be taken into account with this setting. It involves a pressure switch with a hysteresis function. Instruments with this configuration are most frequently installed in industrial applications.
Electronic pressure switches, like the WIKA models PSD-4 and PSD-4-ECO or the A-1200 pressure sensor with IO-Link, operate as ?normally closed? or ?normally open?, depending on task. The following graphics illustrate both switching functions with the respective switch and reset points:
In principle, the following applies: The switch point (SP) is greater than the reset point (RP) and the start of measuring range (MRS) is always smaller compared to the end of measuring range (MRE). This rule could be easily understood with settings for ambient air pressures.
Sale : Control of vacuum pressure pump
On the other hand, setting the switch points in the vacuum range and thus, ultimately, the switching function, requires more attention. To illustrate this, let?s take the control of vacuum pressure pump, for example, which must maintain vacuum pressure between -0.7 bar and -0.5 bar. For the duty described, we select a pressure switch with a measuring selection of -1 ? 0 bar.
The start of measuring range (MRS) is therefore -1 bar, the end of measuring range (MRE) 0 bar. This means: At 0 bar (= start of operation) the switch ought to be closed, as a way to switch on the vacuum pump. If the pressure drops to -0.7 bar, the switch must open and prevent the pump. As soon as the pressure reaches top of the limit value of -0.5 bar, the pump should once more start and run until the pressure has again dropped to -0.7 bar.
ow must the switch points be set within this vacuum range? Let?s take both pictures and translate MRS and MRE:
Here it is clear that the ?normally open? function must be selected, otherwise the pump wouldn’t normally switch on. After entering the switch points, the schematic is obtained, which shows the way the pressure switch functions relative to the example:
Note
Information regarding WIKA?s electronic pressure switches can be found on the WIKA website. Do you want to buy pressure switches? Inside our WIKA online-shop you will find some of our standard designs. When you have any questions, your contact will gladly assist you to.
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