Conditions: tachometer works in an ambient temperature of -20 ~ 50 centigrade, relative humidity below 85%.

Basic error: under temperature 20 ± 2centigrade, the basic error is ±2% of the upper limit.

Temperature effect: when the temperature changes from 20 ± 2 centigrade to -20 ~ 50 centigrade, the tachometer indication value is not more than absolute value of basic error.