LTR-329 lux calculation

I am using the LTR-329 on a custom PCB. It is correctly reporting ambient light readings from both channels to me. However, the datasheet you publish mentions using the calculation in Appendix A to convert the two different readings to LUX. I’d like to do this, but there is no appendix in the datasheet. Can you provide the additional documentation?


Looking at online posts it appears you have to request this information from Lite On. I have sent a request to the Product Manager to see if we can get this information for you. We will let you know when we get the information.

It has been more than a week since I made my request - has there been any progress made on getting the extra documentation for the LTR-329?



I have sent in to a specialist a request to assist on this, I am sorry for this delay.

Hi icrowe,

While waiting for the actual information from Appendix A, you might want to look at the following links. It looks like a few people have used the information from Appendix A of the LTR-329 to write some code. They both use specific multiplication factors for sensors 0 and 1, depending on the ratio of the raw values returned from each. If you take a look at these, it should give you some ideas of how to proceed.

Thank you for pointing out that code. I have found and implemented a similar function.

However, I much prefer to understand the theory behind the equation rather than blindly following another implementation. I know nothing about when the corrections might be in scope, nor why they are ignored when the ratio goes out of a certain range.

In addition, that calculation produces a Lux measurement, which is related to the human perception of available light. In our application, we are more interested in the absolute light levels, or perhaps even the light available for photosynthesis. Understanding the math behind the equation will be a great help in establishing that correlation.

It would be really helpful if Digikey could convince Lite-On to provide that datasheet. My direct emails to their tech support email have been ignored so far.

Ian Crowe, P.Eng. 780 885 9201

Proxilogica Corporation