Hydraulic internal combustion engines having at least one combustion piston not mechanically connected to a crankshaft or any other combustion piston, but instead acting on hydraulic plungers through valving that is electronically controlled to control the piston position and velocity, typically through an intake stroke, a compression stroke, a combustion or power stroke and an exhaust stroke. A measurement part is provided forming a plurality of split channels partitioned by partition boards halfway across a fluid channel, and at least a pair of ultrasonic transmitter-receivers for transmitting ultrasonic waves into the fluid flowing through the split channels and receiving ultrasonic waves that have passed through the fluid. The benzodithiophene containing bisphenyl siloles unit has good dissolution property, high carrier mobility, strong absorbance, wide optical absorption range, and improved utilization of sunlight, and its preparation process is simple, with high yield, and easy to operate and control. A gate-to-source voltage of the power MOS transistor is applied across the second resistor.