Download Nor-840 User Manual - Campbell Associates

Calibrating for FFT Measurements Is Done in Level Mode
The calibration for FFT level measurements must be carried out in Level
mode.
The Tool for this Task
Cal
The Menu for this Task
Press L EVEL to switch to Level mode.
Note that if you set the 0 dB level to a
value different from 2×10 –5, the selected
setting will appear in reverse video on
the screen as shown in the lower Fig. to
the right.
Half of this menu may occasionally appear blank. This will take place whenever the corresponding channel input
has been set to Off.
Press the FFT key to return to FFT mode.
Sound Calibrator
type 1251
If you are going to use the instrument
for vibration measurement it may be
convenient to change the 0 dB level to
obtain dB readings easy to compare with
other vibration measurements. Check
with relevant Standards and conventions to find suitable or commonly used
0 dB levels.
114.0 dB
1000 Hz
Although you may calibrate by just keying in the sensitivity, we always recommend that you use a calibrator. This is
the only way to ensure proper operation
of the entire measuring chain including
the transducer(s).
A
G
B
H
C
I
D
J
E
K
F
L
M
N
Norsonic offers three different sound
calibrators (available separately) to
cover the requirements of the IEC 942
class 0L, class 1 and class 2. The model
shown here is our class 1 calibrator, the
Nor-1251. Note the adaptor designed to
per mit the use of 1 " as well as ½ "
microphone cartridges.
A Sensitivity of channel 1
B Ch. 1 units (dB or engineering units)
C Auto-calibration level of channel 1
D Sensitivity of channel 2
E Ch. 2 units (dB or engineering units)
F Auto-calibration level of channel 2
If You Change the 0 dB Reference Level
G Level of ch. 1 measured with the
selected time constant
H 0 dB level of ch. 1
I
Initiate auto-calibration of ch. 1
J
Level of ch. 2 measured with the
selected time constant
K 0 dB level of ch. 2
L Initiate auto-calibration of ch. 2
M Calibrator frequency
…an indication is provided
48
N Polarisation voltage setting