You should break up your test procedure into a series of applications of force. For example "I twist the device like this (insert diagram with your hands here)", then "I pull up on the device like this (another diagram)".
Now get some spring force gauges or similar and try to estimate the level of forces you apply to the assembly. ...
You could get 3 compression springs for your 1/2/3 levels of tip. Very high spring rate for #1, medium for #2 and low for #3, depending on what you need. The limit could be once you fully compress the spring (all the coils touch), that much force is how much should be needed to tip over whatever you're talking about.
Rain gauge tipping bucket data loggers are quite small. The whole thing is the size of a cookie tin. Bucket size (resolution) is about 1 cc.
Decent explanation in the video below.
With infinite budget, there are fantastic thermal micro-flow sensors, though they too have issues for drip-drip type situations.
One thought, still same overall concept as the tipping bucket, could be to send the flow in a clear tube oriented vertically, with a normally-closed solenoid valve at the bottom. Have your automation optically detect (conceptual ...
The "three plate" method has been used as the basis for precision manufacturing/inspection. This
is a decent summary, it's pretty ingenious and only requires dye and abrasives.
This will teach you everything you need to know and then some, "Foundations of Mechanical Accuracy".
A variation of the tipping bucket - this is used for constructed wetlands to ensure an intermittent feeing of the wastewater.
The water enters a container. The outlet of the container is near the bottom, a flexible piece of tubing is connected to this outlet that serves as a hinge for a short piece of pipe. at the end of the pipe, theres a swimmer.
How it ...
there is a whole genre of "square block" videos on YouTube by various machinists. The standard tool seems to be the lathe.
But really, you are asking how to set up a machine to be perpendicular.
apropos, video for your edumatainment