How can I measure the U value?

With the thermometer tm210 and the U coefficient module which allows to calculate the thermal transmittance coefficient of a wall (U coefficient).

U characterises the quantity of heat that goes through a wall in continuous operation.

It is a key point to determine thermal leak. So it allows to estimate the insulation of a wall: the lower the value, the more insulated the wall.
For building renovations, this coefficient is one of the most important values to estimate the their loss and their energy use.