Whether mechanical or electronic, precision torque wrenches require calibration because the internal mechanisms can wear, fatigue, or become jolted out of accuracy by a drop or a misuse.
In order to ensure accuracy, it’s recommended that torque wrenched be calibrated regularly; at least 5000 torque cycles or once per year. And if it is dropped or under extreme use, calibration may be needed more frequently.
A calibration system measures a torque wrench’s accuracy. Most torque wrenches are easily brought back into tolerance by means of simple adjustments and/or parts replacements made by trained staff (see Calibration Training.”)
Many companies and facilities with numerous torque wrenches purchase their own calibration system and have staff trained to do torque calibration in-house, as this can save money and reduce downtime vs sending torque wrenches to an outside facility (see Cost/Benefit Calculator.)