This article addresses the robust (in the disturbance decoupling sense) design problem of fault detection (FD) filters for uncertain multi-input-multi-output (MIMO) sampled-data systems with fixed-point quantisation. The only available signal is the output variable. A design technique for a deterministic FD observer coupled with a stabilising controller is proposed such that ultimate boundedness (asymptotic vanishing if quantisation is absent) of closed-loop trajectories and estimation error is guaranteed, robustly with respect to disturbances affecting the continuous-time system. A test-function is proposed for detecting the occurrence of actuator faults in the plant. A simulation study on a vehicle suspension system is also reported.