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When using Siemens positioners, customers encounter various problems; below are two common ones. 1. What is the purpose of the internal and external exhaust vents in Siemens positioners? The piezoelectric valve of the Siemens positioner is equipped with a switch that allows selection between OUT and IN. If OUT is selected, the purging gas is not purified internally but is discharged directly through the positioner’s outlet. If IN is selected, a small amount of air will be released into the interior of the actuator’s housing, keeping the actuator chamber at a slightly positive pressure. This enables internal purging, which helps to ensure the proper functioning of the actuator and prevents the intrusion of hazardous gases such as corrosive or flammable gases. 2. How is a two-wire Siemens positioner wired, and is additional power supply required? For two-wire valve positioners, as long as the current is ≥3.6 mA – which constitutes a current-source signal – the LCD will light up and the positioner can operate, provided that there is a 4-20 mA opening signal from the regulator or control system. The current output provided by some control systems is sometimes less than 3.6 mA, but it is necessary to ensure that the output current remains at least 3.6 mA during use; this is something we need to pay special attention to when configuring them. The above has introduced the common problems that may arise when using Siemens positioners. As you use it, the more you understand these issues and the more knowledge you acquire, the deeper your understanding of the locator will become, and you will be able to use it more flexibly.