Weight measurement display


Designing a machine for bulk materials and I have a few questions.
The idea is that the actuator will me to push some loose material for example sugar, after entering the program, for example. "5 lb", I would like to, there was the measurement of the weight of displaying on the display and the spilling and the timing of these 5 lb closed pipe by which is poured into sugar.

I would like to use for this module HX711 and strain gauge and a display for measurement and display of the weight (I think it is a good thing), but I do not know how the sensor applied to the measured off me the 5 lb sensor close to me that pipe that no further poured, because the setpoint program has been reached.

Now the question is whether the sensor is needed, or just write a program that once measured the preset values ​​and the measurement itself shut me that pipe?
Whether he is the meaning of such a thing to do, because of the time, the issues of connection and costs?