Loopback Test: (continued)
Calculate the Standard Deviation:
Using the data collected, calculate the average area counts for Toluene. Typically this value
is around 950. Then calculate the%RSDwhich is usually less than 0.5%. Youmay notice
that there is a small magnitude of error between theCHANNEL 1andCHANNEL 4 area
counts. This is due to theD/A converter andnot the
AID
converter. Since the loopback test
measures the PRECISIONof the
AID
converter and not itsACCURACY, thisminor
discrepancyis insignificant.
SaveYour Loopback Test as aCONTROL
FILE:
If youwish to run this test again or if you
continuewith the next stepandmodify the
Peakwin.ini file, youwill need to save the
loopback parameters as aCONTROL FILE.
In the FILE·SAVECONTROL FILE screen,
type in loopback.con and click OK,
Modifying the Peakwin.ini File, (optional)
..
_'
~.......,...,~~~· I"""''''':'''''J
If desired, any inaccuracyof theD/Aconverter can be adjusted by attenuating the
LOOPBACKOUTPUT tomatch the input signal. This adjustment can bemade by entering
the line "LoopbackFactor=X" in the [Lawson] section of the PEAKWIN.lNI file located in the
WINDOWS directory. The default value of 'X' is 0.098.
NOTE: Changes to the Peakwin.ini file will not be recognized unless the
PeakSimple application is restarted. After you have obtained the average area count for
Toluene on CHANNEL 1, exit PeakSimple by pressing
'Q',
then 'Y'.
To calculate the newvalue for 'X', first determine the average area counts of a specific
peak for CHANNEL 1and also determine the area count of the corresponding peak on
CHANNEL 4. Next, divide the CHANNEL 4area count by the CHANNEL 1area count.
Multiply this ratio by 0.098. Substitute this newvalue for 'X'.
For example, using602.chr as the chromatogramfile, the toluene area count for
CHANNEL 4 is953. If the average area count of toluene onCHANNEL 1 is 931 then the
ratiowould be 953/931
=
1.0236. Multiply 1.0236 x 0.098. the answer is 0.1003128. Round
this newvalue for 'X' to 0.1003.
