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

Chassis is on the bench in the EE shop, with cover off.
	powered with a dual channel power supply with +/-18 (+18.2, -18.1)
	Current draw on positive leg is 260 mA, 110 mA on negative leg. Consistent with test report.
	Once powered on,
		All expected lights turn on.
	Connected DB25 breakout to front of chassis "Preamp Chamber Interface".
		DCPD A channel: +leg = pin 5, -leg = pin 18, BNC shields both connected to GND = pin 13.
	Connected DB9 breakout to back of chassis "To AA/ADC Whitened Output"
		DCPD A channel: +leg = pin 1, - leg = pin 6, BNC shields both connection to GND = pin 5.


Remember, 1:10 whitening filter is ON with the Whitening Disable relays OFF.


SR785 Setup (by hand, didn't want to waste time figuring out GPIB setup)

Freq
	Repeat: Single Shot (don't continuously repeat sweep once done)
	Start: 0.1 Hz (TBD)
	Stop: 102.4 kHz (TBD)
	Type: Log (log-spaced frequency vector)
	Auto Res.: OFF

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

Display Setup
	TOP TRACE
	Measure Group: Swept Sine
	Measurement: Freq. Resp
	View: Linear (Magnitude, i.e. not in dB)
	Units: 
		dB Units: OFF
		Pk. Units: OFF
		Phase Units: deg
		dBm. ref impedance: 50

	BOTTOM TRACE
	Measure Group: Swept Sine
	Measurement: Freq. Resp
	View: Phase
	Units:
		dB Units: OFF
		Pk. Units: OFF
		Phase Units: deg
		dBm Ref. Impedance: 50
	
Source
	Auto Level Ref: OFF
	Amplitude: 1.0 V_pk
		2023-01-23's adventure needing 3V was apparently because the SR785 accessory box's DB9 power input wasn't *really* plugged in.
		After plugging in securely, can get great data with only 1 V_pk.
		Also scaled down ADC input range accordingly,
		Scaled back settle *cycles* from 1 to 2 to save time.
		

	Source Ramp Rate 1 V/sec, but
	Source Ramping OFF (Since we're driving down to 0.1 Hz, and our *start* frequency is 0.1 Hz (i.e. we're sweeping *up*, we don't want to waste any time ramping this *too* in addition to the settle time between sweep frequency changes.)
	Offset 0.0 V (hmmm... maybe we should? Later...)

Input Setup 
	Input Source: Analog
	Input Config:
		CH 1 (Both Channels)
		Mode: A-B (positive legs into A, negative legs into B)
		Coupling: AC	(0.16 Hz)
		AA filter ON
		Wt filter OFF
		Autorange UP ONLY

		Input Range (for 1.0 V source amplitude, 50 ms / 5 cycle integration):
		CH1: +4 dBVpk
		CH2: +22 dBVpk

	Transducer Params: (all as default; unused in this style of measurement)
	Tach Input: (all as default; unused in this style of measurement)
	Playback Config: (all as default; unused in this style of measurement)
	Auto Offset OFF
		
Average Setup
	Step / Impulse response of a basic 1:10 zpk filter is 0.1 sec. 
		(there's probably some math that would predict that for me, but I tossed it into matlab and asked it to do it for me.)
	Adding a 10 kHz pole *shortens* the impulse *time*, but increases the impulse *amplitude*.
	So, a settle time of order 0.1 seconds is in order.

	Frequencies higher than 0.1 sec = 10 Hz should use settle time, and below 10 Hz should use cycles (and one cycle should be plenty). 

	Settle Time = 100 ms (101.56 ms)
	Settle Cycles = 1
	Integration Time = 50 ms (50.781 ms)
	Integration Cycles = 5
with freq = [0.1 102.4e3] and 200 points, this takes 911 seconds = 15 minutes

Output
	Hard Copy Button ASCII Dump
	Bitmap Printer PC X 8 Bit
	Bitmap Area Graphs
	Vector / Plotter PostScript (doesn't matter, unused)
	Destination Disk File
	File Start Number 0
	

Good deal. 
Starting with 
DCPDB Whitening ON, since that's where I left off yesterday.
Only have changed input source voltage, response channel input ranges, and reduced settle cycles, so frequency vector should be the same, allowing for comparison with yesterday.

All data looks much better.

2023-01-24_OMCDCPDWhitening_MeasSetup_mag.TXT
2023-01-24_OMCDCPDWhitening_MeasSetup_pha.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDA_WhiteningOFF_0p1to102p4e3Hz_1Vsrcinput_mag.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDA_WhiteningOFF_0p1to102p4e3Hz_1Vsrcinput_pha.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDA_WhiteningON_0p1to102p4e3Hz_1Vsrcinput_mag.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDA_WhiteningON_0p1to102p4e3Hz_1Vsrcinput_pha.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDB_WhiteningOFF_0p1to102p4e3Hz_1Vsrcinput_mag.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDB_WhiteningOFF_0p1to102p4e3Hz_1Vsrcinput_pha.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDB_WhiteningON_0p1to102p4e3Hz_1Vsrcinput_mag.TXT
2023-01-24_OMCDCPDWhitening_OMCA_DCPDB_WhiteningON_0p1to102p4e3Hz_1Vsrcinput_pha.TXT




OK -- now starting to explore the non-linearity.
0.25 V	20, 21 (CH1/CH2 +4/+22 dBVpk input range)
1.00 V	22, 23
2.50 V	26, 27 (+10/+30)
3.00 V	28, 29 
3.50 V  30, 31 (+12/+30)