Information from the strain sensor is fed to a Pico sampler and is
converted to torque information through bespoke software.
Instructions for the device use are provided to users via a Graphical
User Interface (GUI).
The results have been presented in various studies by the
authors (Yoxall et al., 2006, 2010a), and showed that for males and
females there was a significant drop in strength with age, and that
by 70 years of age, statistically 50% of women would not be able to
access 50% of the jars they bought. Similarly the results showed that
15% of women of any age would struggle with 50% of the jars they
bought; indicating that openability of jars of this type is a signifi-
cant problem.
The authors have also attempted to study ease of access using
analytical techniques (Yoxall and Janson, 2008). Simple mathematics
showed that the limiting torque that a consumer can apply
to open a container is governed by Eq. (1).
Tm ¼ mhcNAre (1)
where, mhc is the coefficient of friction between the hand and the
container cap surface, NA is the minimum human grip force
required for opening and re is the external radius of the container
lid.
Hence the torque a person can generate is effectively governed
by six things (Rowson and Yoxall, 2011), namely:
1. their age
2. their gender
3. their grip strength
4. the coefficient of friction between the hand and the jar
5. their wrist strength
6. the diameter of the container