MK:440 Environmental Noise Microphone
Page 6 of 13
The standard version of the MK:440 has a 4-20mA current loop which outputs a current level,
expressed in milliamperes that is proportional to the sound level with either a 'Fast' or 'Slow' Time
Weighting. The choice of time weighting is a factory set option made at the time of purchase.
To calibrate the MK:440 an 94dB acoustic calibrator must be used. The connected system should
then adjust the interpreted level to 93.7dB, see the example below for how to do this.
The output is always weighted with the ‘A’ frequency weighting which is the most commonly used
frequency weighting for the measurement of environmental and industrial noise levels.
The 4-20mA current loop output is ideal for integration to many process measurement and control
systems where your own system loggers and software can provide an accurate representation of the
'live' noise levels and also store data.
Your own interface system will need programming with a simple formula which is outlined on your
Factory Configuration Information sheet.
For Example:
For a unit with a range of 64 to 134 dB (the default setting if not specified)
Sound Pressure Level
dB = (10 x I) +20
(Where “I” is the output current in mA)
Therefore, in this example an output current of 7.4mA would represent a noise level, L
A
, of
94.0dB(A) as shown below:
dB(A) = (10 x 7.4) +20
dB(A) = 74 +20
dB(A) = 94
Please check with our technical department if you need confirmation about the settings of your
equipment or if you need any other technical guidance.
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Installation
Once you have received shipment of your new MK:440 Noise Sensor unit, follow the next stages to
setup and install the equipment.