MATLAB: How to transfer a continuous signal to a discrete signal in Simulink

Question

Someone suggests that I should use "zero-order hold" ,but when I try to drag and drop one "Discrete Derivative" block after the zero-order hold, an error appears. When I drag and drop one "Derivative" block after the zero-order hold,it works well,which means that zero-order hold can not discretize the continuous signal. How can I transfer a continuous signal to a discrete signal in Simulink?

Answer 1

Use a Quantizer block http://www.mathworks.com/help/simulink/slref/quantizer.html