3 407744 & 407766-en-GB_v5.4 11/17
Operation
Theory of Operation
The 407744 sound level calibrator generates a 94dB sine wave at 1 KHz. The 407766 generates a
94dB and a 114dB sine wave at 1kHz. When a microphone from a sound level meter is inserted into
the calibrator, the sound level meter picks up the signal and displays the signal in dB (decibel) units.
The sound level meter should be adju
sted (if necessary) to match the calibrator’s output signal as
closely as possible (see diagram).
Procedure
1. Insert the microphone into the
calibrator’s microphone cavity as shown;
ensure that
it is fully inserted. Use the ½” microphone adaptor (supplied
attached to the calibrator)
for ½” microphones.
2. On the 407744, s
lide the function switch to the ‘I’ (Power On) position. As
soon as the unit is powered, the calibration tone is generated. On the
407766, slide the function switch to the 94dB or the 114dB position as
desired. The calibrator generates its signal as soon as the switch is set.
3. Read the
sound level meter’s display. The sound level meter should read
94dB or 114dB depending on the
calibrator’s setting. If the sound level
meter does not match the calibrator
’s signal (within specification), adjust it
as explained in the Operation section (typically a front or side-panel pot
adjustment). Refer to diagram at right.
4. Slide function switch to the OFF position, and remove the microphone.
Battery Check
On the 407744, c
heck the condition of the battery by moving the function switch to the ‘Battery test’
position. The Battery status LED should illuminate if the battery is OK. If it does not light, replace the
9V battery. On the 407766, the POWER-ON / LOW-BATTERY LED glows brightly when the battery
is fresh and dimly when the battery is weak.
Battery Replacement
Lift off battery compartment cap (shown in the Description section) to access the two (2) 9V
batteries. Remove the batteries and replace with new alkaline 9V batteries. Replace the cap.
Never dispose of used batteries or rechargeable batteries in household waste.
As consumers, users are legally required to take used batteries to appropriate
collection sites, the retail store where the batteries were purchased, or wherever
batteries are sold.
Disposal:
Do not dispose of this instrument in household waste. The user is obligated to
take end-of-life devices to a designated collection point for the disposal of electrical and
electronic equipment.