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.
[B]Self Powered.[/B] 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
[B]Loop Powered.[/B] 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)
[B]System Powered[/B]. 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!