Larson Davis System 824, Technical Reference Manual

Page: 198 / 673

6-4 824 Reference Manual 9/29/09
With this instrument the SLM and RTA functions are
operating simultaneously. The primary indicator range of the
SLM function is 80 dBA, sufficient for most applications.
In operation, the instrument measures four sets of frequency
spectra; the running instantaneous spectrum, the L
eq
spectrum, the spectrum associated with the maximum SPL
level that occurred during the measurement and the
minimum bin by bin spectrum. It also gives you a time
history record and Ln centiles. The time history record
stores up to 38 parameters of your choice, including RTA
Leq, RTA Max, or RTA Min, which is determined by the
Time History setup under the settings menu.
SSA Measuring Ranges
By using a 24-bit DSP processor, the digital filters of the
System 824 meets the specifications of IEC 61260 - Class 1
and ANSI S1.11-1986 Type 1-D over a linearity range
exceeding 80 dB. The dynamic range of the analysis
function, from noise floor to overload, is 85 dB (typical).
Eight ranges are available, providing gain to +50 dB and
attenuation to -20 dB in 10 dB steps.
The following presents the Measuring Ranges available for
SPL, Peak and 1/3 Octave Filter measurements for the SSA
instrument:
A-weighting, C-weighting, and Flat are measured to
ANSI S1.4 and IEC 60651 standards for SLM linearity.
1/3 octave filters listed are measured to the IEC 61260
standard for Class 0 linearity which is ±0.3 dB. The num-
bers in the table represent SPL levels with a typical
Measurement Range (SSA mode only)
0dB Gain 10dB Gain 20db Gain 30dB Gain 40dB Gain 50dB Gain
NF Start End
Range
NF Start End
Range
NF Start End
Range
NF Start End
Range
NF Start End
Range
NF Start End
Range
AW 33 48 128 80 24 38 118 80 15 28 108 80 8 23 98 75 7 20 88 68 6 20 78 58
CW 32 48 128 80 23 38 118 80 16 28 108 80 9 23 98 75 8 20 88 68 8 20 78 58
FLT 32 48 128 80 25 38 118 80 21 33 108 75 21 33 98 65 26 33 88 50 23 40 78 38
16.0 2 45 128 83 2 35 118 83 1 25 108 83 2 25 98 73 -1 28 88 60 1 23 78 55
31.5 3 43 128 85 1 35 118 83 1 23 108 85 2 25 98 73 -4 22 88 66 -4 23 78 55
63.0 4 40 128 88 0 33 118 85 1 23 108 85 0 22 98 76 -7 15 88 73 -7 18 78 60
125 2 40 128 88 -2 27 118 91 -3 28 108 80 -2 18 98 80 -9 11 88 77 -8 8 78 70
250 3 37 128 91 -3 25 118 93 -3 15 108 93 -4 15 98 83 -10 8 88 80 -9 8 78 70
500 12 33 128 95 4 25 118 93 -3 15 108 93 -4 13 98 85 -10 6 88 82 -10 8 78 70
1000 10 32 128 96 2 20 118 98 -4 15 108 93 -5 13 98 85 -10 6 88 82 -10 8 78 70
2000 15 32 128 96 6 20 118 98 -2 15 108 93 -5 13 98 85 -8 8 88 80 -8 8 78 70
4000 14 32 128 96 7 20 118 98 0 15 108 93 -2 13 98 85 -6 8 88 78 -6 8 78 70
8000 14 32 128 96 7 20 118 98 1 15 108 93 -1 13 98 85 -2 12 88 76 -3 13 78 65
*NF is noise floor
Start = start of linearity range