Do Empower and Agilent calculate noise in the same way? - WKB99451
ENVIRONMENT
- Empower 3 SR3
- Empower 3 FR5
ANSWER
Detector Noise is manually calculated and compared to Empower results using its native formula (see TECN1852433).
When using Excel's Linear Regression formula and calculating the Residual Standard Deviation of y (se(y)), this formula gives the same value calculated when using Detector Noise in Empower.
One of the ways Agilent represents Noise is using the formula by taking the Standard Deviation of the linear regression and multiplying by 6. As we determine that the SD of a linear regression is equivalent to the Detector Noise formula, to calculate an equivalent to Agilent Noise, create a custom field by taking Detector noise * 6.
ADDITIONAL INFORMATION
As noted in PCS#45410, when calculating Detector Noise or Detector Drift, the data points to use include starting on the Start Time but only until one data point before the Stop Time identified on the Noise and Drift tab in Empower's processing method. For example, if the Start time is 4 minutes and Stop time is 8 minutes, use the data points starting at 4 minutes all the way to one point before 8 minutes in calculating Detector Noise or Detector Drift. Also, the export of raw data needs to include up to 14 precision from Empower to allow accurate comparison of calculations.
References:
TECN1852433 (previously TN0000127) Detector Noise and Drift https://www.waters.com/waters/support.htm?lid=1852433&cid=511442&type=TECN
Agilent Noise calculation excerpt (reference document a10424.doc) https://www.agilent.com/cs/library/Support/Documents/a10424.pdf
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