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6. Move to the next area and repeat steps 4 and 5.
7. When finished with survey or when 16 events are accumulated, press ON/OFF to exit
EVENTS.
At any time, even when accumulating data, the current or any previous event data may be
displayed. Press EVENT key until the desired event is displayed. Press any other key to display data for
that event.
If the CODE/HL3 key is pressed it will display the current time for the current event and the start
time of previous events. It will also cycle through HTL, LTL, and 3 dB.
To determine when a representative sample has been taken, press Lavg/Leq for the current event.
If the value does not change by more than a few tenths of a decibel over a few minutes, the data should be
valid for that area.
Effects of Operator's Presence
Any object or surface can act as a reflector or absorber of sound. An operator or person wearing
the dosimeter is also a reflector of sound and affects the microphone performance. The M-27 is designed to
read correctly with the microphone in a random incidence sound field without the presence of reflecting
objects.
The recommended placement of the microphone for personal noise monitoring is on the shirt
collar, high on the shoulder, and away from the neck as far as practical (see Figure 6). If the noise is
directional, it is generally the best practice to place the microphone near the ear which receives the most
noise exposure.
If the M-27 is to be used as a hand-held instrument the microphone should be mounted on the
MB-1 microphone bracket (see Figure 7). It may either be clipped to the bracket or the clip removed and
the microphone screwed to the bracket. The bracket is then attached to the belt clip on the back of the
instrument. If desired the complete unit can be mounted on a tripod (see Figure 8). The microphone should
be pointed upward forming approximately a 70 degree angle with the noise source. It should not be pointed
at the noise source.
Use with Windscreen
To prevent wind from blowing across the microphone and causing erroneous measurement of
sound level, the model WS-5 Windscreen should be used. It is recommended that the windscreen be used at
all
times. Insert the microphone in the windscreen and gently pull it over the Velcro strip.
Using a Printer
The M-27 can print out to Centronics compatible parallel or serial printers at 300, 600, 1200, or
2400 baud (see Figure 9). It can also send various line feed and carriage return combinations to
accommodate different printers. It is necessary that the printer and M-27 agree on protocol and that the
proper cable be selected for a printout.
Serial Printers
Check the printer manual to set printer to serial and desired baud rate. If switches in the printer are
changed, make sure the printer has accepted these changes. This may require turning the printer off for a
few seconds and turning back on.
Check printer interconnections to determine proper cable including male and female pins on the
connector.
Set the internal switches in the M-27 to agree with the printer. It is not necessary to reset the M-27
when printer switches are changed.