Electrical circuit for pressure sensors: when is a sensor active, so when passive?

When using pressure sensors, the output signals 0 ? 20 mA, 4 ? 20 mA and DC 0 ? 10 V are generally chosen in order for the sensor signals to be evaluated and further processed. For this, the signal output of the pressure sensor is usually connected to a corresponding input card in the PLC.
In this context it could often be confusing, as the day-to-day using the terms ?active?, ?passive?, ?current source?, ?voltage source?, ?current sink? and ?load? are often wildly mixed together. Any electrical signal processing always takes a voltage supply (an ?active part?) and a ?load?, such as a pressure sensor, which represents the ? Confessions ?. Sometimes the active section of the interconnection is also described as an electrical source/voltage source and the passive part is referred to as a ?current sink?. In order that an electrical circuit can function, current must flow in a circuit ? even when an instrument is usually known as lots, the current is not consumed because of it, rather it only flows from the current or voltage source through the load and back to the existing source.
This works only if an ?energy gap? exists between current source and current sink, so the power source operates actively (= sending out current) and the current sink passively (= current flows through it) . Therefore, an interconnection of two current sources or two current sinks will not operate normally. This situation is complicated in day-to-day application:
When does a pressure sensor work passively (current sink) so when does it work actively (current source)?
So how exactly does the input card in my PLC operate?
As a rule of thumb, you can understand that 2-wire sensors usually work passively and thus need a dynamic PLC input card. It is difficult with 4-wire sensors, since, for example, a 4-wire flow sensor includes 2 wires for a separate voltage supply and 2 wires for a dynamic or passive 0/4 ? Insult . Hence, it is imperative to check the datasheets for the sensor and PLC input card used.

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