Hi,

Right click on panel element > Display tab > Interface style > check "Tachymeter"
(tried to translate the label from french interface, hope I am not wrong)

When doing this the computer freezes, then black screen, as if it is a kernel panic, and so I needed to reboot.

% cat /etc/debian_version 
stretch/sid
% uname -a
Linux poils 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-3 (2015-04-23) x86_64 GNU/Linux
% dpkg -l | g xfce4-sensors
ii  xfce4-sensors-plugin                   1.2.6-1+b1

I don't know what other information I could give you, I tried looking for interesting stuff in kernel.log, but could find something relevant to me. Maybe better if you ask me ?

Cheers