Monday, 25 September 2017

Wind Chime Wavelength Calibration

This post describes how to perform a wavelength calibration using Wind Chime. The methodology is the same as used on the 7205 UV Diode Array:

  1. A scan of the wavelengths from 198nm to 1000nm of the output of the Xenon lamp.
  2. The data is analyzed to find all the peaks in the scan
  3. These peaks are compared against a set of reference wavelengths
  4. If there is a match you can send the corrections to the Spectrophotometer

Press START SCAN to scan each wavelength from 198nm to 1000nm, this will take some time.

Progress is shown

Once done, enter your reference wavelengths. The app will already have populated the fields with default values, to remove a reference just delete the number.

Press ANALYZE, Wind Chime will find all the peaks in the scan and then attempt to find an overlapping match with the reference peaks.

The status will show the number of peaks found, here it is 16. To find more peaks, reduce the slope threshold, to find less increase the slope threshold. Press analyze to recompute.

If you don't get a match remove one of the more troublesome reference points and press analyze again.

Once you are happy press SUBMIT PEAKS, this will first send an ERASE CALPOINTS command to the spectrophotometer and then ADD CALPOINT commands for each of the reference/match pairs.

The spectrophotometer will store the calibration data in its onboard FRAM

Friday, 15 September 2017

Wind Chime v1.5

This releases sees two new screens, Photometrics and Alignment. There are also a few bug fixes and minor improvements. The navigation menu has now been divided up into categories to make it easier to find a particular function. Find Home command will now wait up to 100s before timing out.


Press blank to take a dark and blank reading, press sample to take a sample reading. You can change the wavelength from the wavelength screen, see below.

There is also a USB logging function that will log each sample to a file called photometrics.csv on an USB memory stick. Makesure you insert a USB stick before turning on logging and that when you finish, you turn off logging and unmount the drive (see my earlier post about removing USB sticks).


The wavelength screen has been revamped, there are now 2 presets for the stray light test.

Optics Alignment

The alignment screen is similar to he 73's alignment screen and has been designed for a engineer to aligned the optics.

The CALIBRATE ENDSTOP button will find the 0nm (white band) and store it in the PCB.

See the release notes for further details

Thursday, 7 September 2017

WindChime v1.4

New Features for version 1.4 of WindChime

  • Bootloader support
  • EMC Testing

Menu highlighted to show new screens
Note that you can update to v1.4 from v1.3 from within the app using the Update screen


Before using the bootloader functions, ensure you are first connected to the spectro. Note also that /dev/ttyO1 is now the default setting, however the app will remember your setting.

Currently the spectro is in Bootloader mode, press JUMP

The spectro is now in Application mode

In order to use the spectro, you will need to issue the jump command to put the Spectro into application mode.

Launch Settings

WindChime will launch automatically on boot up, you can set to connect automatically and send a jump instruction.

EMC Testing

The EMC Test screen will periodically send out the current date and time. You can either send to a printer or to a file on a connected USB memory stick. Note that if you are having problems with your USB memory stick please see How to safely eject a USB memory stick.

Ejecting USB Memory Stick

This post will describe how to safely eject a USB memory stick from the Bibby Beagle Bone Black android computer.

Follow these instructions incase you are having problems reading/writing to a USB stick.

Swipe down to reveal the notification drawer

Press the settings icon

Press the Storage option

Press Unmount shared storage

Press OK

You can now safely unplug your USB memory stick