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.