122 Micromate Operator Manual – 721U0201 Revision 6
15.1.2. Microphone Calibration
The microphones used with the Micromate are calibrated independently allowing them to be used
with any Micromate unit. The microphone is placed in a calibration chamber along with a
calibrated and traceable reference microphone.
------- Microphone being Calibrated
Calibrated
Reference
Microphone
-------- Calibration Chamber
Microphone Calibration System
The chamber will then be operated at the frequencies required to meet the ISEE standard and the
microphone output signal monitored. The ISEE microphone response is checked every 0.5 Hz from
1.0 Hz to 500 Hz. The microphone will then be adjusted to ensure the response meets the actual
standard at all of the different frequencies. The results are then saved, printed and provided as
part of the calibration report. If the microphone is being returned for its annual calibration an As
Found report will also be generated. The As Found report will follow the same procedure as above
except no adjustments will be made. This report is used to document the actual response of the
microphone sensors in the state in which the unit was received.
Below is a sample graph of the ISEE standards. This graph show the amplitude verses frequency
response of the actual sensor (thin line) and the limits for the standard (thicker line). A passing
sensor will have its response completely within the limits of the standard.
Sensor Response
ISEE Response Limits
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