Can we measure the angle of a leaf in order to conclude whether it closing its leaves or not.
Yes ,We can …Here is the method described by @lakshmy from CUBE SN Nattika.
Datas Taken from CUBE National meet presentation 2022
Leaf angle titration. The angle measured between midrib of the leaf and the stem.
The angle is measured using online protractor.
Procedure
A) observe the one single leaf and measure the change in the angle at different time intervals.
B) Initial one hour of waking up of leaf  Take photos of leaves 15 minutes intervals.
C) Later onwards  Take photos of 1 hour interval.
D) Last one hour of sleep up Take photos of leaves 15 minutes intervals.
We can see last one hour of interval the angle of the leaf is rapidly declining and comes to zero.
Photos taken by @Theertha
This is the graph made based on the observations. We can see the angle is not always constant. @Enas @~Vijaya Tilak @~Susanta Tanti @Theertha @Shrudhiga @Sunitha Mam @Chithra Mam @Kiran ma’am @Abhijeet Cube
Datas taken from CUBE National meet 2020
Screenshot of chatshaala session
Comparison between sleepwake cycle in Phyllanthus vs Fruitfly
Online Protracter
Following data collected by @Lakshmy from CUBE SN Nattika
Graph made using above data
Conclusion:

By measuring the angle at different time intervals the phyllanthus plant show significant change in the angle from 5pm onwards.

Between 9am  5pm the angle is not constant. It varies in each hour.

From 5pm onwards there is drastic change in the angle.

At 6:30pm the plant goes to deep sleep.