Instruction manual

26
Preparations
Calibration
Before starting a measurement, the NA-27 must be calibrated. There are two types of
calibration, namely electrical calibration and acoustic calibration using a pistonphone.
When compensation for atmospheric pressure is not required, it suffices to perform elec-
trical calibration only.
Electrical calibration
Calibration is carried out by setting the unit to the CAL mode. If the display reads 94.0 dB,
calibration was completed successfully. If the reading is different, or if level calibration of
connected equipment is required, perform the following steps.
1. Set the power switch on the side of the unit to ON.
2. Use the SLM / 1/1 / 1/3 key to call up the measurement screen.
3. Press the CAL key to activate the calibration mode.
At this point, frequency weighting is temporarily set to "C"; it will return to the
original setting when the CAL key is pressed once more.
4. Use the LEVEL UP/DOWN keys to set the measurement range to 100.
If the measurement range is set to a value other than 100, the CAL indication
flashes and correct calibration cannot be carried out.