A tension meter is a precision instrument used when screen making. It's used to measure the tension of stretched screens, and they can vary in costs depending on if they are mechanical or electronic. It measures the amount of deflection in the fabric when the weighted meter is placed onto the stretched fabric. The deflection is measured in Newtons-per-centimeter (N/cm). Many manufacturers provide an ideal or recommended Newtons-per-centimeter of tension for varying mesh counts. Because the meter is a precision tool, it should be handled with care and stored in a proper carrying case to avoid damage.
Source: Encyclopedia of Garment Printing