3M 1200 User Manual - General Overview
1200/2200 Sound Level Meter Operator’s Manual
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General Overview
2. GENERAL OVERVIEW
2.1 The Display:
The LCD display provides a numeric readout in 0.1dB increments
along with a LOBAT (low battery) indicator. The LOBAT indicator
will turn on when the voltage of the battery is too low to allow an
accurate reading.
A plus sign ‘+’ will appear on the left side of the display if signal
peaks cause an overload condition in the electronics. If the signal falls
below the measuring range, ‘UR’ (under range) will be displayed.
2.2 Meter Controls:
2.2.1 OFF/PAUSE/RUN Switch:
• OFF - In this position the power is removed from the instrument.
• PAUSE - In SPL mode the meter continuously displays sound pres-
sure level according to the RESPONSE and WEIGHTING settings. In
other modes the meter will display the appropriate value for the previ-
ous RUN or ‘---‘ if no run time has been accumulated. The meter
automatically updates the current reading at a rate of once per second.
• RUN - Causes the meter to begin calculating the frequency
weighted equivalent continuous SPL. All SPL measurements are inte-
grated into a single number representing the equivalent SPL for the
entire measurement period. This measurement will continue until the
meter is placed in the PAUSE mode or reset. Maximum RUN time is
100 hours or as long as the battery lasts.
2.2.2 SPL/LEQ/RT/MAX/MIN/%OL Response Switch:
This six position switch determines the display mode of the meter.
• SPL - In the SPL mode the numeric display provides a reading of
the maximum sound pressure level measured during the previous
second.
• LEQ - In the LEQ mode, the display indicates the integrated , or
average level for the RUN period. If no RUN time has been accumu-
lated the display shows dashes.
1200/2200 Sound Level Meter Operator’s Manual
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General Overview
• RT - In the RT mode the display shows the elapsed time of the
current or last RUN. The RT mode consists of two or three displays.
The first is RUN TIME seconds ‘
. The second is RUN TIME
hours minutes ‘
. Pressing the CAL button while in the RT
mode toggles the meter between these two displays. If the RUN TIME
exceeds hours, there will be a third display that will show hours up
to ‘h
. If no RUN time has been accumulated the display shows
dashes.
• MA - In the MA mode the display holds the highest reading
encountered during the RUN period. If no RUN time has been
accumulated the display shows dashes.
• MIN - In the MIN mode the display holds the lowest reading
encountered during the RUN period. If no RUN time has been
accumulated the display shows dashes.
• OL - In the OL mode the display shows the time that the circuitry
has been overloaded as a percent of RUN TIME. If no RUN time has been
accumulated the display shows dashes.
• UR - If an Under Range indicator designated as a "-"(minus) symbol
appears on the display, then this indicates the Sound Pressure level is
below the measuring range set on the Sound Level Meter.
2.2.3 FAST/SLOW/PEAK/IMP Response Switch
The Response Switch controls the rate at which the meter responds to
changing input signals. Most sound measurements are done with the
response set to SLOW S . The FAST F response is generally used when
measuring short duration noises such as moving vehicles. PEA P is
useful when measuring the absolute pea of the sound pressure wave.
IMPULSE I is used for impulsive or transient sounds.
The Response switch positions are as follows
• FAST F -
millisecond time constant. See Figure
ecay Rate . d per second.
• SLOW S - second time constant. See Figure
ecay Rate . d per second.
• PEA P - microsecond time constant.
• IMPULSE I - millisecond rise time constant, . second decay time
constant. See Figure