Negative polarity Zener barrier

For negative polarity Zener barrier , the cathode of the zener diode is connected to ground...So how this circuit work for DC supply?? as per my understanding ,by this connection type then the zener diode should be acting as a normal diode and all the current will go through it and no current should go to field!!! please anyone can explain for me especially I am using one with dual channels to supply smart positioner , should I select positive or negative polarity zener barrier ???and why???

a zener diode is a normal diode that will break its blocking at a certain voltage. The problem is the wattage as all this energy, need to be dissipated. so in most cases a resistor is used to lower the amperage.

Negative polarity for NPN output circuits, where you would want the negative side fuse protected.
You are correct about how Zeners work. Select a positive type for your application, and wire it so the Zeners will not act as diodes in normal operation.