Operating Instructions - nthallen/keutsch-hcho GitHub Wiki

Loading HCHO Interface

The algorithms that control all aspects of Harvard FILIF can be accessed via Cygwin installed on the HCHO GSE

  1. Open up a Cygwin window

  2. Type cd /home/CH2O/

  3. Type ./doit in order to start the HCHO instrument algorithms. The interface only loads if the electronics box is powered on and you're connected to the same network as the instrument.

Navigating between windows: The keystroke to use when navigating between windows is 'CTRL-A-n' to go forward and 'CTRL-A-p' to go back.

  1. To get a graphical interface, start Matlab and type rt_hcho

  2. In order to initiate plotting you have to click on DFS -> CONNECT in the upper left corner

Quick Start: Automated Data Collection

As of March 2024, the ./doit command will initiate standard FILIF instrument operations and automatically issue the three commands listed below.

Quick Start: Manual Data Collection

Assuming that all electronics and the laser are powered up and the pump is running, the following commands should be issued to start data collection. This command sequence also assumes that the scan range is already defined (such as scan start, scan stop, and step size) as well as the offline position relative to online (offline delta), the dither step, and the number of points collected at the online and offline position.

> swStat Pressure Control Activate starts a PID algorithm that adjusts the setpoint on the bypass MFC in order to get a pressure reading of 115 Torr inside the detection cell. If the bypass MFC setpoint goes to zero or full scale without reaching a pressure of 115 Torr, then the needle valve adjacent to the inlet of FILIF should be opened or closed accordingly.

> swStat Chop Dither Enable ensures that the dithering functionality is enabled. Dithering is helpful to stay on the online position between full scans and helps to minimize the number of times a full scan needs to take place during data collection.

> swStat chop start 30 Minute Scan Interval (also available in intervals of 1, 5, and 10 minutes; values can also be adjusted in algo). This command formally starts data collection by first performing a full spectral scan and using the reference cell signal to identify the online position. After a full spectral scan is performed, the algo automatically starts tuning the laser between the online and offline positions based on the settings defined under Laser Control. After 30 minutes (or whatever interval is used) another full spectral scan will be performed before going back to the online and offline positions.

A note about data collection: The algorithm runs on the onboard computer on the HCHO instrument. Raw data is also saved onboard the HCHO instrument. This is immensely helpful since it means the Lenovo laptop can be disconnected from the network (or turned off) and the HCHO instrument will still be collecting data with the settings that you last applied. True story from a study at MIT: Since the Lenovo laptop randomly turns off or updates itself, this feature has meant we were still collecting data in the background!

Proceed to Stopping Data Collection and Saving Data