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Student meeting 13.05.2013 Reliability analysis of the ADC in the BLMDP

Student meeting 13.05.2013 Reliability analysis of the ADC in the BLMDP. Vegard Joa Moseng BI - BL. The circuit:. Measurement Methods. About the ADC circuit . The input monitoring system has two different measurement levels.

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Student meeting 13.05.2013 Reliability analysis of the ADC in the BLMDP

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  1. Student meeting 13.05.2013Reliability analysis of the ADC in the BLMDP Vegard Joa Moseng BI - BL

  2. The circuit:

  3. Measurement Methods About the ADC circuit • The input monitoring system has two different measurement levels. • One is the Fully Differential Frequency Converter (FDFC) which measures detector output currents from 10pA to 30mA. In this measurement method, the ADC is attached to the diff. output of an integrator in the input monitor. • The other is the Direct ADC Acquisition (DADC) which measure detector output currents from 80uA to 200mA. The ADC is attached to an input resistor on which the voltage drop is measured. Operation The ADC is integral for the operation of the input monitor. For the FDFC, the number of accumulated counts are combined with the ADC values to calculate the integrated loss over a 2µs period.

  4. Criticality Integration in the system • For each detector connected to the BLEDP, there is one input monitor circuit and one ADC. There is therefore 8 ADC’s per BLEDP. • The ADC is critical for the operation of both the measurement methods, and is thus critical for one channel in the BLEDP. Therefore, the loss of an ADC is equivalent to the loss of a detector. • The ADC has two main failure modes that affect the operation of the BLEDP; complete failure (no output), and erroneous output (from either internal failures or erroneous inputs). Detection As a part of the new acquisition system, an improved connectivity check is planned to be implemented which is capable of frequently testing the entire detector supply chain. This should therefore be able to detect a erroneous output by it’s reference current. This will however not indicate explicitly that the ADC is giving erroneous outputs but it will be sufficient for a false dump to take place and the changing of the BLEDP card, and thus maintaining the operation of the machines without there being a blind failure.

  5. MTTF: Reliability analysis • The values are for a whole BLEDP card, which means it’s the weighted average value of 8x ADC circuits who are themselves identical. Ambient and operational temperature is set to 40 degrees. • Failure rate: 8.023E-07 • MTTF in hours: 9.972E+06 • MTTF in years: 1138.3 years Severity ranking 1. No effect: Non-critical failure such as filtering. 2. Maintenance: Failure in redundant components and other failures that allow for continued operation but should be fixed as soon as possible. 3. False dump: Failures that causes loss of critical functionality and/or safety, will cause the system to abort (dump the beam). 4. Blind failure: Failures where you are unable to detect erroneous information, or where you have no protection when you expect to have .

  6. Risk Priority Numbers

  7. A total of 27 failure modes in the ADC circuit will cause a false dump, but all are detectable and have a very low probability of occurrence, so no special actions, such as redundancy, is warranted. Comments

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