VIPER — Vacuum Ionisation Pressure Experimental Readout

VIPER is a Python-based tool for reading pressure data from a Kurt J. Lesker 392 Series Ionization Gauge and logging it to HDF5 files.

Requirements

• Nix (for the development environment).
• Ion Gauge 392 connected via RS485/USB.

Nix

• Nix is two things: a package manager and a programming language used to interface with the package manager.

• On some Linux distributions, Nix can be installed using that distributions package manager. For example, Nix can be installed on Ubuntu using apt by running the command:

sudo apt install nix-bin

• Otherwise, Nix can be installed here: https://nixos.org/download/

• This project utilises Nix flakes which are currently an experimental feature within Nix. To learn more about flakes (which you should) go here: https://nix.dev/concepts/flakes.html. To enable Nix flakes, add this line to the file /etc/nix/nix.conf

experimental-features = nix-command flakes

Ion Gauge 392

• VIPER makes use of the KJLC ASCII protocol provided by the Ion Gauge 392.

• By default, the Ion Gauge 392 is set to the BINARY protocol. To change this, go to "SETUP COMMS" using the screen of the Ion Gauge 392. Then, scroll down to "FORMAT" and change from "BINARY" to "ASCII".

Note

VIPER should work with other Ion Gauge models that make use of the KJLC ASCII protocol format, such as the KJLC 354 and 300 series convection gauge models. BUT, VIPER has not been tested on these other models.

Configuration

• There are two configuration files within VIPER:

1. Gauge configuration (configs/gauge/example-gauge.conf)

• Example:

[Serial]
port = /dev/ttyUSB0
baudrate = 19200                                    # needs to match the gauge baudrate
address = 01                                        # needs to match the gauge address
timeout = 1.0                                       # see core/ion_gauge_354.py for more info
min_delay = 0.05                                    # minimum time between sending commands via serial port (taken from manual)

2. Recording configuration (configs/recording/5-min-intervals.conf)

• Example:

[Logging]
store_data = true
h5file = ${VIPER_DIR}/data/vacuum_data_5min.h5      # path to h5 file
interval = 5.0                                      # time between each recording in seconds
duration = 300                                      # total number of pressure recordings (0 for infinite)

Warning

Currently the interval is about 3 seconds shorter than how long there actually is between each measurement. This is due to inefficient writes to h5 files. Therefore, if you want to record measurements every 10 seconds, an interval of 7.0 seconds will give close to 10 second intervals.

How to use

• Clone github repository.

• Then, in the same directory as the flake.nix file, run the command:

nix develop

• or if that doesn't work, try:

nix develop .#default

• This enters you into a Nix shell with all the required packages and variable names. You can leave the Nix shell by running exit in the command line.

• Finally, run the command:

viper /path/to/gauge_config.conf /path/to/recording_config.conf

• For example, you can run VIPER using the example configuration files by running the command:

viper configs/gauge/example-gauge.conf configs/recording/5-min-intervals.conf

Output

• VIPER stores all information in h5 files.

• The h5 file that VIPER writes to is defined in the recording configuration file. If this h5 file exists and is formatted correctly, VIPER will append new data to the existing data in the h5 file.

• The structure of the h5 file is:

Index | Timestamp (s) | Ionisation Gauge (Torr) | Convection Gauge 1 (Torr) | Convection Gauge 2 (Torr)

• If the Ion Gauge 392 doesn't give back a pressure after being prompted to, that pressure value will be stored as 0.

• On top of storing data to h5 files, VIPER will also continuously print data read from the Ion Gauge 392 to the console.

• If the Ionisation Gauge is turned off, the gauge will send a pressure of about 9.8 x 10^8 Torr. That pressure will be printed to the console but will be stored as 0 Torr in the h5 file.

• If either of the Convection Gauges are turned off, that gauge won't send a pressure back. That pressure will be converted to None in the python code and that None is printed to the console. If this occurs, similar to the Ionisation Gauge, 0 Torr will be stored in the h5 file.