Physical Setup
https://dcc.ligo.org/LIGO-D2200215-v1

Chassis is on the bench in the EE shop, with cover on and mosts screws screwed in.
	Powered with a dual channel power supply with +/-18 (+18.1, -18.1)
	Current draw on positive leg is 170 mA, 100 mA on negative leg (reading from the power supply screen). Consistent with test report.
	Once powered on,
		All expected lights turn on.
	Connected DB25 breakout to front of chassis "Preamp Chamber Interface".
	For each channel measured
		- DCPD A channel: +leg = pin 5, -leg = pin 18, 
		- DCPD B channel: +leg = pin 1, -leg = pin 14,
	During the measurement, the positive leg is shorted to the negative leg with a clip-lead to clip-lead cable
		This makes sure there's no differential noise at the input from floating input pins
	AND both legs are shorted to pin 13 (Chassis GND) with clip-lead to clip-lead cables.
		This establishes chassis GND as the voltage reference.

	Connected DB9 breakout to back of chassis "To AA/ADC Whitened Output" to readout output referred noise (which should be compared to the ADC noise)
	For each channel measured
		- DCPD A channel: +leg = pin 1, -leg = pin 6, 
		- DCPD B channel: +leg = pin 2, -leg = pin 7,

	For each channel measured (they were measured independently) these output legs were connected differentially to the SR785 channel 2. Clip leads to BNC-style, with red connected to the positive / negative legs, and black (BNC shield) connected to pin 5 (chassis GND).
    SR785 will subtract A - B, so we plug the positive leg to A, and the negative leg on B.

Now for the SR785 software setup (by hand, didn't want to waste time figuring out GPIB setup)

Display Options
	Display: Live
	Format: Single
	X-axis: log
	RPM Frequency: OFF
	Grid: ON
	Grid Div: 10
	Phase Suppress: 0.0e+00
	d/dx window (%): 0.5

Display Setup
	Measure Group: FFT
	Measurement: FFT2 (for channel 2)
	View: Log Mag (really, log amplitude)
	Units: Vrms/rtHz
		dB Units: OFF
		Pk Units: rms
		PSD Units: ON
		Phase Units: (deg)
		dBm Ref Imped: 50

Freq (Three Spans used)
	Started with
	Span: 400 Hz
	Line Width: 500 mHz
	Acq. Time: 2 sec
	FFT Lines 800
	Base Freq: 102.4 kHz
	Start: 0 Hz
	Center Freq.: 200 Hz
	End Freq: 400 Hz

	Then for the 4 Hz to 3.6 kHz band, just hit "Span Up" three times.
	Then for the 32 Hz to 25.6 kHz band, just hit "Span Up" three more times.

Input
	Source: Analog
	Analyzer Config: Dual
	Input Config (only CH2 matters)
		Input Mode: A-B
		CH2 Coupling: AC
		CH2 Input Range: -50 dBVpk
            Used auto-range from SR785 and it settled at -50 dBVpk
		AA Filter: ON
		A-Wt Filter: OFF
		Ch2 Auto Range: Up Only (though auto range was OFF)
    Auto Offset: OFF

Average
	Compute Avgs: Yes
	Averaging Type: Linear/ Fix Len
	# Avgs: 30 ('#' stands for 'Number of')
	Display Avg: RMS
	Time Record Incr.: 100%
	(All else as default)

Output:
    MATTERS
        Hard Copy Button: ASCII Dump
        Destination: Disk File
    Does not matter
        Bimaap/Printer: PC X 8 bit
        BITMAP AREA; Crafts
        Bector/Plotter: Post-script
    (File number starts: SCRN<FileStartNumber>.txt)

! Always format disk before getting started !

Disk:
    Disk Upkeep:
        Format: Floppy (all data will be lost: ENTER)

!! Did you remember to turn off the Auto Offset? !!

To save:
    Press 'Print Screen'
    WARNING: Floppy disk light is the one to look at before ejecting

(Delete when done!)
Format to save:
2023-01-30_OMCDCPDWhitening_S2300003_OutputVoltageNoise_OMCA_DCPDA_WhiteningOFF_0p5Hzto400Hz.TXT
2023-01-30_SR785_NoiseFloor_0p5Hzto400Hz.TXT

Saving:
2024-05-22_OMCDCPDWhitening_S2300002_OutputVoltageNoise_OMCA_DCPDA_WhiteningON_0p5Hzto400Hz.TXT
2024-05-22_SR785_NoiseFloor_0p5Hzto400Hz.TXT