Guess what? You have just invented a SNAP-AIMA-i module! :mad:
The SNAP-AIMA-iSRC does simplify wiring and reduce installation time, but at a premium cost. A lower cost alternative is to use field wiring terminals and a common field power supply for SNAP-AIMA modules and where necessary, SNAP-AIMA-i modules for channel isolated instrumentation.
Here is my dummy guide for understanding the wiring scenarios.
Self Powered. An instrument that uses an internal power supply to provide 24VDC loop power. Often found when the instrument requires higher power or additional electronics. Instantly recognisable as it needs 4 wires. (Two for power supply and two for 4-20mA signal
Loop Powered. An instrument that requires an external 24VDC power supply. (Instantly recognisable as it only requires 2 wires (Two for 24VDC over which the 4-20mA is imposed)
System Powered. An instrument that "expects" that the I/O module provides the 24VDC power. (In reality it has no idea if the 24VDC is from the I/O module or a loop power supply)
- The only SNAP current module which can actively supply 24VDC loop power is the SNAP-AIMA-iSRC.
- All other SNAP current modules are passive and require the use of a 24VDC loop power supply or self powered instruments.
- Do not mix power supplies on a non isolated module.
- On a SNAP-AIMA-iSRC, do not use supply terminals 1&2 unless both transmitters are system powered.
Its that simple!