Using multiple LEDs at different angles at the same time to improve accuracy

Hardware, PWM, and Optics
1

Hey everyone,

is it possible to use more than one IR-LED at the same time to improve the accuracy? For example, use 135° up to an OD of 1, 90° between 1 and 3 and 45° above 3?

Cheers

2

Hi @EBTPio,

That’s a neat idea! Nothing like that is implemented yet though.

If you wanted to test some pairs of angles, in the config.ini, there’s a section [od_config.photodiode_channel] that tells the software where the PDs are. By default, it’s

1=REF
2=90

which means PD1 is in REF position, and PD2 is in 90 deg. You can change this to something like:

1=135
2=90

and put PD1 into the 135 spot. Then your live data will have two signals show up: 135 and 90. (you lose the REF signal though, so your data may have some minor artifacts as a result).

3

Hi @CamDavidsonPilon

Thank you. This is helpful. I’m thinking about using two angles to monitor OD as well because I’m working with cells at OD>4. I have few questions relating to this.

  1. Is it possible to move the photodiodes to X1 (as 45) and X2 (as 90)? I have just realized that the opening holes at X1 and X2 are bigger than 90 and 135 angles. What is the reason of that different opening holes for the OD monitoring?

  2. How will the growth rate calculation be based on if we used two angles at the same time?

  3. Will we see separated lines for raw OD or just one line from both angles on UI?

Best regards,
Sansanee

4
  1. Hm, interesting question! Yes, X1 and X2 are shaped differently as we expected users to use them as LED outputs (ex photosynthetic cultures). However, they could work for PDs. My worry is that you’ll get some artifacts from light scattering off the stir bar. So, my answer is: it’s possible, but maybe control angles first: both PDs in 90deg pockets, etc.
  2. The growth rate calculator will combine the two signals into a single growth rate. There’s no control as to how this blending occurs.
  3. You will see two lines in the raw OD, one for each single. They will be labelled with the PD too. Example: pio01-1 and pio01-2 represent the PD1 and PD2 signals respectively in worker pio01. This will make answering 1. above easier.
1 Like
5

Thank you for the answers.
I did a calibration once by putting a photodiode at X1. It gave scattering numbers of measurement, might be the artifacts like you said.

6

Hey,

thanks for your answer.