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1Dec. 11, 1997
LEADS Quality Control Systems
Robert Brewer(512) 239-1618
Monitoring Operations Division Network QA Manager
2Dec. 11, 1997
Quality Control (QC)
Quality Control is the overall system of technical activities that measure the attributes and performance of a process, item, or service against defined standards to verify that they meet the stated requirements established by the customer.
3Dec. 11, 1997
LEADS QC Checks During Calibrations
Monitor Voltage and Concentration Outlier Checks Concentration Spacing Check Slope/Intercept Checks - Cal. only Zero/Span Checks Precision/Linearity Check - Cal. Only Converter Efficiency Checks (NOx & H2S)
During Span Checks Monitor Voltage and Concentration Outlier Checks Concentration Spacing Check Zero/Span Checks Linearity Check - Span Only Converter Efficiency Checks (NOx & H2S)
Span Source Audit - Checks the accuracy of the DASIBI 5008 Calibrator every 45 days
4Dec. 11, 1997
Calibration Sequences
Sequences are composed of Levels. Levels - A Level consists of a set concentration from
the DASIBI 5008 calibrator introduced into a monitor for a set number of 5-min average updates. Each Level is assigned a letter code (M, R, S, T, or G) by the datalogger.
Updates - A set number of 5-min updates (usually 3) in each level are allowed for instrument stabilization. The remaining updates (usually 4) are processed by LEADS.
5Dec. 11, 1997
O3, SO2, & CO Cal. Sequence
Level
M*
R
S
T*
G*
Conc. (ppm)
0.4, CO 40
0.3, CO 30
0.2, CO 20
0.09, CO 9
0.0
* Note - Levels used during Span Checks
6Dec. 11, 1997
NO, NO2, & NOx Cal. Sequence
NO2 Conc. (ppm)
0
0
0.4
0
0.3
0
0.2
0
0.09
NOx Conc. (ppm)
0
0.47
0.47
0.37
0.37
0.27
0.27
0.16
0.16
Level
G*
M*
M†*
R
R†
S
S†
T*
T†*
NO Conc. (ppm)
0
0.47
0.07
0.37
0.07
0.27
0.07
0.16
0.07
*Note - Levels used during Span Checks†Note - Gas Phase Titration Levels
7Dec. 11, 1997
Scrubber Bypassed
NO
NO
NO
NO
Yes
NO
NO
H2S Cal. Sequence
SO2 Conc. (ppm)
0
0
0
0
0.09
0.09
0
Level
M*
R
S
T*
T1*
T2*
G*
H2S Conc. (ppm)
0.4
0.3
0.2
0.09
0
0
0
*Note - Levels used during Span ChecksT1 - H2S Converter Efficiency CheckT2 - SO2 Scrubber Efficiency Check
8Dec. 11, 1997
Outlier Tests
1 2 3 4 5 6 7 8 9 10 5 - Min Updates
Stabilization Processed Updates
Average of 4
Limits
Voltageor
Conc.
Next Level
Outlier is found so test is repeated without outlier.
9Dec. 11, 1997
Outlier Tests - Second Pass
1 2 3 4 5 6 7 8 9 10 5 -Min Updates
Stabilization Processed Updates
Average of 3Limits
Voltageor
Conc.
Next Level
The first outlier is ignored. Remaining 3 updates are within limits.
Result: Pass with Warning
10Dec. 11, 1997
Concentration Spacing Test
Voltage
ConcentrationG T S R M
- Warning or Failure Limit around Ideal Value
Outside of Limit
11Dec. 11, 1997
Slope and Intercept Tests(Cal. Only)
Voltage
ConcentrationG T S R M
Slope Outsideof Limit
Intercept
²y
²x
Slope = ²y
²x
InterceptLimits
Slope LimitsIdeal Slope
Note: Both Warning and Failure Limits are used in these tests.
RegressionLine
12Dec. 11, 1997
Zero and Span Tests
Voltage
ConcentrationG T S R M
ZeroLimits
PreviousCal. SpanVoltage
PreviousCal. ZeroVoltage
SpanLimits
Zero VoltageOut of Limits
- Ideal Values
Note: Both Warning and Failure Limits are used in these tests.
13Dec. 11, 1997
Precision/Linearity Test(Cal. Only)
Voltage
ConcentrationG T S R M
Note: Both Warning and Failure Limits are used in this test.
Limits
RegressionLine
Out of Limits
14Dec. 11, 1997
Linearity Test(Span Check Only)
Voltage
ConcentrationG T S R M
Note: Both Warning and Failure Limits are used in this test.
Limits Line betweenZero and Span
Out of Limits
15Dec. 11, 1997
NO2 Converter Efficiency Test
The NO2 Converter Efficiency is calculated for the M, R, S, and T concentration levels and compared to an ideal of 100%.
Efficiency is calculated from the change in response of the NOx channel when a level of nitric oxide is titrated with ozone to produce NO2.
Both Warning and Failure Limits are used in these tests.
16Dec. 11, 1997
H2S Converter and Scrubber Efficiency Tests
H2S Converter and Scrubber Efficiency are calculated for the T level only and compared to an ideal of 100%.
Converter Efficiency is calculated from the monitor’s response to the T level of H2S (T) as compared to the T Level of SO2 with the scrubber bypassed (T1).
Scrubber Efficiency is calculated from the monitor’s response to the T level of SO2 with the scrubber bypassed (T1) as compared to the T Level of SO2 through the scrubber (T2).
Both Warning and Failure Limits are used in these tests.
17Dec. 11, 1997
Ideal Values
Ideal values for each of the tests are listed in the Calibration and Span Check reports available from the LEADS Network Status Report Web Pages.
For Each Test, the Ideal Value is subtracted from the Measured Value to obtain the test error. This error is then compared to the Warning and Failure Limits.
18Dec. 11, 1997
Test Limits
All QC tests performed on LEADS calibration or Span Check data have both Warning and Failure Limits except the Outlier Tests. Each Outlier Test uses only one Limit but the test is repeated once if an outlier is detected.
Each Warning Limit is chosen statistically to represent the 3 standard deviation value about the mean error of a test. This means that there should be only a 0.27% probability of exceeding a warning limit if the monitoring system is working properly. DO NOT IGNORE WARNINGS.
Each Failure Limit is chosen to be at least 1.5 times the warning limit and is intended to represent the maximum error that will be tolerated without invalidation of the affected data.
19Dec. 11, 1997
Automatic Data Validation Rules Automatic invalidation of data is based only on whether a QC test passes or
fails. Warnings are not considered in this processing. Failure of a Concentration Outlier test or a Concentration Spacing test
indicates a problem with the calibration system but not with the monitor (except NO2). The Calibration or Span Check event involved is considered invalid and the ambient pollution data is unaffected.
Calibration QC Tests Failure of a Monitor Outlier Test, Precision/Linearity Test, Converter
Efficiency or Scrubber Efficiency Test causes invalidation of ambient data back to the last good Cal. or Span Check and forward to the next good Cal.
Failure of a Slope or Intercept Test causes ambient data invalidation forward to the next good Cal.
Failure of a Zero or Span test causes ambient data invalidation back to the last good Cal. or Span Check.
20Dec. 11, 1997
Automatic Data Validation Rules (Cont.)
Span Check Tests Failure of any test, except the Conc. Outlier and
Spacing Tests, causes invalidation of ambient data back to the last good Cal. or Span Check and forward to the next good Cal.
21Dec. 11, 1997
Span Source Audits QC Span Source Audits evaluate the accuracy of the
CAMS DASIBI 5008 calibrator. Corrective action is required if audit limits are exceeded.
If the audit passes, then the pollutant monitor must be adjusted to agree with the M-Level concentration produced by the CAMS DASIBI calibrator. This sets the Slope of the monitor’s calibration curve to the ideal.
If a Slope Test warning is reported thereafter, then action must be taken to determine if the error was caused by monitor drift or span source drift. A Span Source Audit may be needed if there are no obvious instrument problems.