This is a handy device that anyone can use to help tame Terrible Tensions. It's affordable, very easy to use and comes complete with instructions. This high quality model has an aluminium housing and is easy to read.
We measure tension in grams and the gauge simply allows you to tie the end of the bobbin thread to the gauge hook and while steadily pulling the device away from the machine towards the operator, the centre plunger will show how many grams of force is required to pull the bobbin thread. This is the measurement we use to set the tension.
Typically, between 30 and 50 grams will work well for most machines. It really is a very simple way to determine if your bobbin tension is within an acceptable range.