This paper deals with the problem of designing a controller for multirate sampled systems with slow output sampling and fast input updating rates. An adaptive output estimator based on a reduced first order model of the controlled system will be proposed in order to design an output feedback controller with a fast-rate input updating period. The proposed adaptive output estimator is designed for a reduced first order model of the controlled system and so has relatively simple structure compared with common adaptive observers. The results reported here are validated on an experimental liquid level process system.