
CEL-63x Environmental Noise Meter
72 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
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
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.
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