Status and Preliminary Testing of

the New HyperHyperBus Fault Detector

Work done by CPCP section 10-12.2008Based on Slides from Knud DAHLERUP-PETERSEN

Architectural Design by Reiner DENZAnalysis by Zinur CHARIFOULLINE

❖Preliminary Bus Splice Quality Characterization ( Nano Ohm Meter Function)❖ Voltage Signal Noise Reduction Integration Hierarchy

❖ Differential Analog Bandwidth: 0-200 Hz (tested at 1 kHz)❖ 24bit ∑∆ ADC (modulator frequency: 32768 Hz)❖ Hardware (in QPS) 24bit ∑∆ ADC integration period: 187 mS (5.35 Hz)❖ Firmware (in QPS) moving rectangular integration: 18.9 S (101 samples)❖ Software (in CCC) DC integration time: typically > 10 minutes (this is what counts!)

❖ Feasibility of nΩ Resolution ?

❖Real Time Early Warning Bus Fault Detection

❖ Bus Inductance Compensation (94 µH)

❖ Feasibility of 300 µV Threshold ?

Both functional aspects of the new bus fault detector have

been tested:

Results from Measurements Performed on 27 Oct. at up to 1250 ADCDQQDC Detector Card now linked up to the WorldFip and LHC Logging

Strong Filtering, Sampling Time 187 ms, 100 points Sliding AveragePost Treatment of Data with Labview

380 µV1250 A1 hour

Results from Measurements Performed on 27 Oct.

Voltage during Ramping

1250 A

380 µV

4 A/s4 A/s

Results from Measurements Performed on 27 Oct. at 1250 ADC

Results from Ramping, Flat-Top and Ramp-down

±10 µV

Real Time Noise Floor

Results from Measurements Performed on 27 Oct. at 1250 ADCwith DQQDC Detector

100 nV100 nV

490 ± 90 pΩ

490 ± 90 pΩ

245 ± 45 pΩ / Splice245 ± 45 pΩ / Splice

Zero Closure = 20 nV

~ 1 hour integration / point~ 1 hour integration / point

7

Bus VoltageBus Voltage

Selected DC DataSelected DC Data

50 µV50 µV

375 µV375 µV

4 A/s4 A/s

1 hour1 hour94 µH94 µH

3500 Amp Ramp3500 Amp Ramp 29 October

Results from Measurements Performed on 29 Oct. at 3500 ADCwith DQQDC Detector

8

290 ± 50 pΩ / Splice290 ± 50 pΩ / Splice

200 nV200 nV

580 ± 100 pΩ

580 ± 100 pΩ

Zero Closure = 50 nV

10 min - 1 hour integration / point10 min - 1 hour integration / point

9

500 nV500 nV

650 ± 29 pΩ

650 ± 29 pΩ

Results from Measurements Performed on 30 Oct. at 5000 ADCwith DQQDC Detector

325 ± 15 pΩ / Splice325 ± 15 pΩ / Splice

Zero Closure = 50 nV

Ramp [Amp] Resistance/Splice [pΩ] estimated statistical error [pΩ]

1250 245 45

3500 290 50

5000 325 15

mean 287 28

Repeatability & ConsistencyRepeatability & ConsistencySame Splice

Different RampsDifferent Days

Can we measure better than 1 nΩ ?

YES WE CAN !YES WE CAN !

11

1 µV1 µV

1550 ± 340 pΩ

1550 ± 340 pΩ

Results from Measurements Performed on 30 Oct. at 5000 ADCwith COMPENSATED DQQDC Detector

520 ± 110 pΩ / Splice520 ± 110 pΩ / Splice

671 ± 43 pΩ

671 ± 43 pΩ

335 ± 22 pΩ / Splice335 ± 22 pΩ / Splice

500 nV500 nV

Can we measure better than 1 nΩ ?

YES WE CAN !YES WE CAN !

13

97% Compensated Signal

Residual = 10 µV out of 400 µVResidual = 10 µV out of 400 µV

First Feeble Attempt at Compensation

4 A/s4 A/s

4 A/s4 A/s

Bus VoltageBus Voltage

375 µV375 µV

Uncompensated Bus SignalSerious Attempt at Compensation

Can we have a detection threshold better than 300 µV ?

YES WE CAN !YES WE CAN !

±300 µV±300 µV

4 A/s4 A/s

PC recapture !PC recapture !

Completely Compensated Bus Signal

Completely Compensated Bus Signal

Can we have a detection threshold better than 300 µV ?

YES WE CAN !YES WE CAN !

±20 µV±20 µV

Conclusions fromPreliminary Testing

• Signal noise is amazingly insensitive to cable routing.

– This allows practical routing in the cable trays.

• Barring any unforeseen noise issues, sub nΩ resolution should be possible.

• A 300µV real time early warning threshold is practical.

– But keep in mind that saturation at high field or magnetization at low field may spoil compensation slightly.

– Some variation in splice resistance must be tolerated.

– Some variation in electronic component noise must be tolerated.

– And many unexplored and hence unforeseen noise sources may spoil and consume our threshold margin. (TGV, Bastille Day, etc.)

– A healthy margin must be maintained, as false trips may keep the Higgs away.

– Only after operational experience with the entire system will we know if the threshold really needs to be increased for stability or possibly could be decreased to provide added security. (The threshold needs to be secure but flexible.) YES WE CAN !YES WE CAN !