Why are the electric pen values different?

Why are the electric pen values different?

The electric pen is small and convenient, but because of the low price and relatively low accuracy, the test results are also inductive. As a result, the induction test does not have any reference to its specific value. The test is influenced by the humidity of the air, the dryness of the object in contact, etc. If you want to get the actual value, it is recommended to test it in a professional laboratory to be more accurate.