5 Getting Started
Overload Detection and Underrange
056-652, Rev.D 1100/2100 SLM models
Overload Detection and Underrange
The Overload Indicator is displayed whenever the incoming signal saturates
(overloads) the circuitry. It is the + sign on the left side of the display. If the
overload indicator is on while taking measurements in a Low range, increasing
the dB Range switch should cause the overload to disappear. If you are already
on the highest range setting and an overload condition still exists, the sound level
that you are measuring is beyond the capability of the 1100 due to either an
extremely high rms value or a high crest factor (peak to rms ratio).
Underrange is indicated by a "Ur" in the display. When the noise level drops
below the bottom of the range, this indicator will turn on. Switching to a lower
range will turn it off.
Output Jack
The model 1100 provides an output jack on the bottom of the meter for
measuring the weighted AC signal before the rms/log detector and the DC output
of that detector. This jack may be connected to any load without affecting the
operation of the meter. Connection to low impedance loads
will require correction for the 1 Kohm impedance of this output and will also
decrease battery life. The output jack uses a 3.5mm stereo plug.
Figure 3: Output jack connections
DC Output Function
The Sound Pressure Level (SPL) over the range selected is linearly
represented
by a DC output. The output changes 16.7mV/dB or 1 V/60dB. This output is
primarily provided for connecting a 0 to 1 volt span data recorder.
AC Output Function
This output provides the amplified, weighted AC signal from the input of the
RMS detector.
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