Evan G., Keita K. Summary: We analyzed the measurements made at the end station (see LHO aLOG 30854). The measured delay of a 960 Hz digital sine wave excitation to the output of the analog AI is 205.7 usec. The expected delay is 203.6 usec. The difference of 2.1 usec could be the result of small differences in analog AA/AI electronics. The measurements also reveal the DAC delay = 63 usec (61 usec expected, again probably the difference is the small variability of the AA/AI electronics), ADC delay = approx. 1 usec (<1 usec expected). Additionally, digital excitations are found to be advanced by 61 usec. This is important because we need to independently measure the the timing of the analog signal relative to the witness GPS 1 PPS signal to determine the timing of the ADC. We also independently measure the timing of the DAC relative to the witness GPS 1 PPS signal by using the digital system to produce an excitation that is measured in the analog world. Details: The oscilloscope measurements are analyzed using the duotoneDelay.m script which directly computes the Fourier coefficients of a DuoTone time series with two sine wave signals at 960 and 961 Hz. The Fourier coefficients yield the amplitude and phase, where the phase delay is interpreted as a time delay. The time series input is synchronized to the 1 PPS signal from the witness GPS receiver located at each end station (time series is triggered on the rising edge of the 1 PPS). The oscilloscope is set to produce 1e6 samples per trace. We saved two different duration traces: 1 sec (1e6 samples/sec) and 2 sec (5e5 samples/sec). Oscilloscope ------------ 1 PPS --| CH1 | ==> Time series with pulse leading edge = 0 sec | | Pcal/DuoTone --| CH2 | ==> Fourier coefficient of time series with timestamps referenced to 1 PPS yields delay ------------ Analog measurement Delay (usec) ---------------------------------------- Pcal X excitation (1 sec) 145.2 Pcal X excitation (2 sec) 144.1 Pcal Y excitation (1 sec) 144.4 Pcal Y excitation (2 sec) 144.9 DuoTone X (1 sec) 257.9 DuoTone X (2 sec) 258.0 DuoTone Y (1 sec) 257.2 DuoTone Y (2 sec) 256.6 We saved a 2-second DTT time series of H1:CAL-PCAL*_DAC_FILT_DTONE_IN1_DQ and H1:CAL-PCAL*_EXC_SUM_DQ (where * = X or Y). The time series starts on an integer second. Using the same duotoneDelay.m script, we compute the delay of the digital Pcal excitation signals and the digital DuoTone signal. Digital measurement Delay (usec) ------------------------------------------------ H1:CAL_PCALX_EXC_SUM_DQ -61.0 H1:CAL_PCALY_EXC_SUM_DQ -61.0 H1:CAL-PCALX_DAC_FILT_DTONE_IN1_DQ 340.4 H1:CAL-PCALY_DAC_FILT_DTONE_IN1_DQ 339.8 (Note the 61 usec advance of the excitation signal) To determine the analog output delay of an excitation, we subtract the measured delay of the digital Pcal excitation from the measured analog delay and compute the mean value, yielding a delay of 205.7 usec. We expect a delay of 203.6 usec (61 usec delay from USER model to IOP model, 43.5 usec from phase effect in digital AI, 3 IOP DAC FIFO cycles, 0.5 IOP cycles from DAC zero-order-hold, 0.5 IOP cycles from DAC clock offset, and approx. 38 usec from phase effect in analog AI). The difference of 2.1 usec is likely due small differences in the analog AI filters. To determine the DAC delay, we can remove the analog and digital AI filtering, and the 61 usec delay from USER to IOP models. This yields a delay of 63 usec, compared to the expectation of 61 usec. The difference is, again, likely due to small differences in the analog AI filtering. The ADC delay can be determined using the difference between the measured delay of the DTONE_IN1_DQ channels and the delay measured in the analog DuoTone signals. We also need to remove the analog and digital AA filtering. This yields an ADC delay of approx 1 usec (we expect a delay of <1 usec). Small differences in the analog AA filtering may be the reason for this difference. Analysis script can be found at: /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER10/H1/Scripts/timing/analyzeTimingMeasurements.m