Casella CEL CEL-63X - Manual (Page 76)

CEL-63x Environmental & Occupational Noise Meter
76 Casella CEL
5. Linear operating range
Table 4 shows the lower and upper limits of the linear operating ranges for
electrical input or when using a CEL-251 microphone.
You should add 10 dB to the lower limit shown in this table when using a
CEL-252 microphone.
Table 4. Linear operating range
Weighting 31.5 Hz 1 kHz 4 kHz 8 kHz 12.5 kHz
A 30 to 100 30 to 140 30 to 141 30 to 138 30 to 134
C 32 to 137 32 to 140 32 to139 32 to 136 32 to 132
Z 38 to 140 38 to 140 38 to 140 38 to 140 38 to 140
C Peak 65 to 140 65 to 143 65 to 142 65 to 139 65 to 135
6. Linearity measurements starting point
The starting point for measuring linearity errors is 114 dB.
7. Electrical input
The input device to apply electrical signals to the pre-amplifier is a series
18 pF ±5 % capacitor. You can use the CEL-516-2 line input adaptor for this
purpose. The electrical self-generated noise can be measured with the supplied
shorting plug attached to the CEL-516-2.
8. Self-generated noise
Self-generated noise is a combination of microphone thermal noise and the
instrument‟s electrical noise. Table 5 shows the self-generated noise levels for a
range of conditions.
Table 5. Self-generated noise using a type CEL-251 microphone
Weighting Electrical
Typical dB
Electrical
Max dB
Microphone
Thermal dB
Combined
Typical dB
Combined
Max dB
A 15.0 17.5 16.0 18.5 20.0
C 18.0 21.0 16.8 20.6 23.0
Z 24.0 26.5 16.8 25.0 27.0
Note that the CEL-252 microphone has a typical thermal noise level of
20 dB(A). When using the CEL-252 microphone, the combined typical and
maximum noise levels will be 3 dB to 4 dB higher than the values shown in the
table above.