GainMon (v1.0): DARM Loop Unity Gain Frequency Monitor for the DMT

GainMon currently monitors the unity gain frequency in the DARM control loop. It will eventaully be modified to monitor the MICH and PRC loops as well. The code and documentation for GainMon has been cloned from SenseMonitor.

GainMon uses the open loop gain as a function of frequency at start time to determine the unity gain frequency at all later times. GainMon reads in the loop transfer function (Actuation*Sensing*digital) which determines the initial gain G(f,t=0) at t=0. The dynamic alpha and beta calibration factors are then used to scale the open loop gain to any later time t. G(f, t)=G(f, t=0)*alpha*beta. Once the open loop gain is determined at some later time t, GainMon interpolates the frequency at which the gain is unity and reports this in minute trends.

GainMon generates a report of the following quantities:

The principle forms of output are:

GainMon Output

Gainmon produces the following output at regular intervals (normally once per minute):

Graphical: DMTViewer Plots

The following time series are reported to the DMTViewer (the name of the corresponding channel in the trend files is in parentheses):

Interpreting Plots:

GainMon reports zero or negative values for all of these channels under special conditions.

Html and data files

GainMon writes summary log files and other useful data products.

Running GainMon

GainMon is managed by the Process Manager, and so it should always be running at the sites. If it is missing, please contact Aaron Rogan.

The standard way to start GainMon is

     GainMon -config <file_name>
where <file_name> is a configuration file. Up-to-date configuration files are usually available on the dmt machines (sand, delaronde, etc) as ~ops/pars/GainMon_L1.conf, etc. A sample configuration file for H1 is
    -OSCfile  StateVector.conf
    -OSCcond Both_arms_locked_strict_cm 
    -xmlfile ReferenceCalibration_H1.xml
    -fmin 30.0
    -trend H1
The last entry in the configuration file must be one of H1, H2, or L1. The remaining arguments (which may be invoked in any order) are listed below. Arguments in red are required.

-fmax #         Specify maximum frequency to include in range estimate.
                Default 1400Hz.

-fmin #         Specify minimum frequency to include in range estimate.
                Default 20Hz.

-h, --help      Print usage information, then exit.

-local          Run in local mode.  All output files are dumped in the local directory
                instead of to the default directory specified by the 
                environment variable $DMTHTMLOUT.  The plain-text log 
                file is renamed <GPS_Start_Time>.log.

-logfile <name> Name plain-text version of log file <name>.  Only works if
                -local option is also selected.  Default filename is
                <GPS_start_time>.log (-local mode) or <IFO>_SenseMonitor_CumLog.txt

-max #          Specify maximum number of strides to process before program

-n #            Specify number of sections to divide data into for calculating 
		the noise power spectrum.  The 'stride' variable must be a 
                multiple of this number.  Default 15.

-OSCfile <file> REQUIRED.  Specify the OSC configuration file defining the
                various operating conditions for the interferometer. 
                (If not specified, SenseMonitor will attempt to open
                then ./SenseMonitor_LockLoss.conf.)  SenseMonitor will exit
                if no OSC configuration file can be found.
-OSCcond <cond> Specify the OSC (operating state condition) for which 
                SenseMonitor will compute range estimates.  Default is 

-screen         Update and error messages are sent to the screen instead of
                to the default files <IFO>_SenseMonitor_Log.txt and 

-stride #       Specify length in seconds of data to use for each range estimate.  
                Default 60.

-trend          Write range and calibration data to trend files as minute trends.  
                When writing trends it is recommended that `stride' be a factor 
                of 60 (eg: 15, 30, 60).

-window <type>  Specify data window type for power spectrum estimation, where
                <type> is one of:
                  `hanning' for Hanning window,
                  `blackman' for Blackman window,
                  `flattop' for FlatTop window (NOT RECOMMENDED),
                  `hamming' for Hamming window (NOT RECOMMENDED),
                  `square' for no window (NOT RECOMMENDED).
                Default Hanning.

-xmlcal   REQUIRED. Use dynamical calibration based on a reference 
                calibration file . 


GainMon estimates the strain noise spectrum from the AS_Q data following the calibration notes of Gonzalez et al (2002, 2003). All actual calibration calculations are performed by the FDEasyCalibrate class, which requires as input a specially formatted file containing reference calibration information. These reference calibration files will be produced by the calibration team. The only point that might interest the casual user is that this calibration data should be linearly sampled over a frequency range larger than [fmin,fmax] Hz (see -fmin, -fmax options) and not including 0 Hz or 4096 Hz. GainMon will exit if the calibration data does not cover [fmin,fmax] Hz.

Operating State Condition (OSC)

GainMon requires a file defining the condition under which range estimates will be computed. A good choice for OSC (-OSCcond) is Both_arms_locked_strict_cm. In this case the detector is required to be in common mode, but not necessarily in science mode. A good choice for the definitions file (-OSCfile) is D. Chin's /export/home/ops/pars/LockLoss.conf, which contains up-to-date definitions of standard states.

The user may specify an alternative location and file name at launch. Otherwise, GainMon will search for the file GainMon_LockLoss.conf, first in the directory specified by $GAINMON_OSCCONF and then in the local directory. You can (re-)set the environment variable GAINMON_OSCCONF using a command like

     setenv GAINMON_OSCCONF  directory_path

Known Bugs

  1. None.

Contact Info

Comments, queries, and suggestions regarding any aspect of GainMon are welcome; please email the authors.
Author: Aaron Rogan
Documentation from SenseMonitor written by:
John Zweizig
Patrick J. Sutton
Code Version: 1.0; last modified Nov. 25 2005.
Documentation: last modified Jan. 25 2006.

Laser Interferometer Gravitational-wave Observatory