Spectrum RX I Getting Started Guide . 47
Calculating the signal-to-noise ratio
5.
Type
noise X 2600 2500
and press
enter
.
The noise in region X over the range 2600 to 2500 cm
-1
is calculated.
6.
The three results of
noise
appear in the command line.
The three results (in %T) are:
•
peak-peak -
the peak-to-peak noise;
•
rms -
the root mean square noise;
•
trend -
the linear trend in the noise.
S/N is given by the signal amplitude (in this case, 100%T) divided by the peak-
to-peak noise (in the illustration above, 0.0360%T).
When the Spectrum RX I executed the Noise command above, it displayed the
results on the screen and also stored those results in its memory. The
Spectrum RX I can store up to 100 numeric
V-va iables
called V0 through V99.
The results of the Noise command were stored in V0, V1 and V2. They remain
in these V-variables until the Spectrum RX I is switched off or until they are
overwritten (for example, by the results of another command).
r
You can use the result for peak-to-peak noise that the Spectrum RX I stored in
V0 to calculate the S/N.
The value for the peak-to-peak noise stored in V0 is in transmittance, not %T
(100 x transmittance = %T). The 100%T line has a transmittance value of 1.0.
This means that the S/N is given by 1.0 ÷ V0.
7.
Press
1
/
v-var
0
.
1/V0
appears in the command line.
