The Granville‑Phillips Series 354 Micro‑Ion module is a compact ionization vacuum gauge that combines the smallest ion probe with built‑in control electronics and supports DeviceNet, RS‑485 or analog outputs for high‑vacuum applications (10⁻⁹ to 5×10⁻² Torr). Common failure modes include power‑supply dropout or voltage spikes damaging the front‑end circuitry, filament burnout leading to loss of ion current, sensor drift from contamination or aging of the iridium filament, and communication faults such as bad DeviceNet/RS‑485 termination or broken cable connections. For initial troubleshooting verify the module’s 12 V DC supply (check output voltage and ripple), inspect the probe filament for visible damage or discoloration, and confirm proper termination and signal integrity on the chosen interface; also review any error codes displayed on the module’s LCD or transmitted via the digital bus.[oss-gpt-20b]