Fluke Proving Unit provides a safe method to verify that your electrical test tool is operating properly before you conduct any live tests. The concept of Test Before Touch (TBT) involves testing your meter against a known live source before and after the actual measurement. This sequence verifies that your test tool is operating properly during the actual measurement. Using the PRV240 reduces the need for personal protective equipment (PPE) when a known voltage source is not available for verification of your tester or multimeter before test before TBT are performed. PPE is still needed for absence of voltage testing when appropriate.