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I need help guys.
Hi eric I'll remove that zenner diode.
Here is the new schematic.I also added a 0.1uF cap near AD input.
Also what about adding a 100mA fuse in the current loop.
Is my diagram ok?
to get 1A through 250 Ohm you need 250V. all 4-20mA loops are powered by much lower voltage such as 24V. at 24V even if sensor is short circuited, current will not exceed some 100mA.
If your concern is damage to the 250 ohm resistor due to a shorted sensor, I would suggest just using a higher power resistor.
The 10K part will protect the PIC even from 24 volts across Rsense.
As for the capacitor at the input to the PIC, make sure you take into consideration the delay that it will add to the signal.