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Calibration of the ELMB analog measurements

Calibration of the ELMB analog measurements. R. Fantechi 25/11/2011. The need for the calibration. Two main points 101:1 input ratio of the ELMB with 0.1% resistors Should not be a problem, but the input impedance is 101 Kohm , so there is an effect in combination with what described below

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Calibration of the ELMB analog measurements

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  1. Calibration of the ELMB analog measurements R. Fantechi 25/11/2011

  2. The need for the calibration • Two main points • 101:1 input ratio of the ELMB with 0.1% resistors • Should not be a problem, but the input impedance is 101 Kohm, so there is an effect in combination with what described below • Differentkindsofvoltages sent to the ELMB withdifferentseriesresistors • 10 KOhm for the preamplifier regulators • 1 KOhm for voltages and currents of preampli power supplies (excluding positive currents for which R=0) • Transceiver and pre power supplies measurement pass also through a low pass filter with 1 KOhm in series

  3. Transceiver connections

  4. Regulator connections

  5. Preampli PS connections 1 The division by 2 of VP is done with a resistor matrix which preserves the 1+1 Kohm series resistance

  6. Preampli PS connection 2

  7. Calibration procedure • Measure the voltages on the input connector to the ELMB, with ELMB disconnected • Use a precision voltmeter with an input impedance of 1 GOhm • Connect the ELMB and measure with the OPC Wizard the raw values read • Fill an Excel file and compute the correction factors as • Vvoltmeter/ELMB*1000000 • Analyse the Excel data to spot problems and to define data to be remeasured • Iterate

  8. Statistics • 576 values measured in 10 classes • Regulators (VP, VC, VN), Transceivers (V, I, T), Preampli PS (VP, VN, IP, IN) • 510 good at the first measurement • 28 remeasured • 33 not powered • 5 with problems • In the analysis phase build histograms for each class of values (10 in total) • Estimate the measurement error from the RMS • 0.1% expected from the ELMB • For I, IP, IN we have found an effect due to a large quantization of the ELMB measurement (30 microvolt)

  9. Correction factor • Values expected • Regulators VP, VC, VN: 111 • Transceiver V,I,T: 102 • Power supplies VP, VN, IN: 103 • Power supplies IP: 101 • Measurements • Regulators: VP 106.1±0.1 VN 111.9±0.4 VC 111.8±0.2 (1) • Transceiver: V 102.0±0.5 I 102.2±0.5 T 102.1±0.3 • Power supplies: VP 102.8±0.2 VN 103.1±0.3 • Powersupplies: IP 101.2±1.6 IN 101.1±1.4 (2) • Still to be explained • Low measured values, strongly affected by the ELMB quantization

  10. Conclusions • The measurement campaign has been useful to spot problems in the power supply system • The measured factors almost agree with the expectations • Each class has a good distribution of values • We need at least 1% measurement error, so I propose to use “educated averages” as global factors • Regulators: VP 106 VN,VC 112 • Transceivers: 102 • Power supply VP, VN 103 • Power supply IP, IN 101 • Refinement could be applied following better understanding of problems

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