A flexible digital-input channel can accept potential-free contacts as well as PNP and NPN sensors, but the common reference and logic mode must match the field device. Incorrect assumptions can produce inverted states, permanent ON conditions or no response.
Dry contacts
A dry contact contains no external voltage. Connect the contact between the input and the designated common, then configure the field-power or field-ground arrangement required by the module. Confirm wetting current and contact suitability for low-energy electronic inputs.
PNP and NPN sensors
A PNP sensor sources positive voltage when active and therefore requires a sinking input arrangement. An NPN sensor sinks current to field ground and requires a sourcing input arrangement. Verify the sensor output type rather than relying on wire colour alone.
Logic levels and filtering
- For the documented Titania input, PNP ON is 13–30 VDC and OFF is 0–5 VDC.
- NPN ON is 0–5 VDC and OFF is 13–30 VDC.
- Select filter time according to contact bounce and the narrowest valid pulse.
- Excessive filtering can suppress legitimate high-frequency input events.
Technical basis: Titania Modbus DI-8 DO-8 datasheet TTN-DS-2026-001, issued 19 July 2026. Confirm the current hardware, firmware and controlled document revision before implementation.
