OPTO 22 SNAP-PAC-R1 User Manual page 86

TROUBLESHOOTING I/O MODULES: FREQUENTLY ASKED QUESTIONS
loop through the module. A ground loop through the module could result in almost
anything, from inaccurate readings to catastrophic failure of the module.
SNAP analog modules, like any high-level electronics, require protection from electrical
noise in high-noise environments, such as installations near arc or plasma equipment or AC
inverters. If the SNAP analog system is to be installed in such an environment, be certain
that the system is enclosed in an appropriate enclosure.
SNAP PAC R-Series Controller User's Guide