Key Functions
SOUND LEVEL The sound level, at the end of each second, with slow (1
second) time constant. SOUND LEVEL and PAUSE TIME are
the only functions active during pause time.
PEAK LEVEL Peak sound level detected in any 1/16 second interval plus 3
dB. For impulses longer than 100 milliseconds the error is
less than -2 dB.
SLOW MAX The maximum sound level with slow time constant.
HTL L-AVG The integrated average of the slow time constant sound level
and an internal switch determined exchange rate and high
threshold level measured in decibels.
HTL DOSE The percent dose of HTL L-AVG with a selectable 8
hour criterion level.
HTL TWA The time weighted average in decibels. It is equal
to an 8 hour continuous sound level which would produce
HTL DOSE.
LTL L-LAVG Same as HTL L-AVG with a low threshold level.
LTL DOSE Same as HTL DOSE with a low threshold level.
LTL TWA Same as HTL TWA with a low threshold level.
3 dB LEQ The integrated average sound level measured in
decibels with a 3 dB exchange rate, no time constant, and no
threshold.
3 dB DOSE The percent dose with a selectable 8 hour criterion
level.
3 dB SEL The total sound exposure level in decibels inte-
grated over 1 second.
PAUSE TIME Length of time unit has been in pause mode. The MICRO-15
is in pause mode after the PAUSE key, the ON/OFF key, or
reset keys have been pressed or the battery has been
connected.
RUN TIME Length of time the unit has been in run mode.
OL TIME Length of time the unit has exceeded the overload
level. Overload data is revised up to 16 times a second. Only
complete seconds are displayed.
CODE (See code section.)
Controls
ON/OFF When pressed for 5 seconds unit turns off and dis-
play becomes blank. When unit is off pressing the key will
turn it back on in the pause mode. Memory is not erased
when unit is turned off. When off the battery drain is very low.
PAUSE Stops accumulating data. Only sound level and
pause time functions are active. When key is pressed, the
pause time is displayed.
RUN Starts or continues accumulating data. Display
shows run time.
PRINT Causes 15 functions and 8 parameters to be
printed. Unit should be in pause mode to stop accumulating
data while printer is operating. Pressing ON/OFF key will
cause printer to stop.
RESET Pressing both PAUSE and ON/OFF for 5 seconds
will cause the unit to reset. After the unit has reset a "0" will
be displayed and the unit will be in the pause mode.
Printer Output
The printer output is compatible with many RS232-C serial printers and the
serial inputs of computers. The data is sent in ASCII code. It is sent
asynchronously at 600 baud.
The printout consists of 29 lines with 15 characters in each line. See Figure
5.
The top section of the printout details the internal parameter switch settings.
The lower section gives the results of the 15 readouts. The SPL (Sound
Level) printout is the only function that prints the instantaneous value at the time
of printing; it may not be a meaningful number. This is because the unit is always
measuring as a sound level meter even if it is in the pause mode.
Each line is terminated with an 0A HEX line feed character.
Each character consists of 11 bits sent at 600 baud made up of 1 start bit at
5 volts, 8 ASCII character bits sent least significant bit first with zero set at 5 volts
and one at 0 volts, a parity bit always set to 5 volts, and 2 stop bits set at 0 volts.
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