Sorry, I meant a light sensor. I also used the Light Meter app with my phone, but needed it to receive calls and messages. A second phone would be as expensive as a second hand /new lux data logger, but with extended battery life.
I could never figure that out either. So . . . . .
In my Reed Instruments, I always zero the hours/minutes/seconds just before I start a runtime graph. I have to do this every time I do a runtime, but it only takes seconds once you figure it out. Excel then accepts this as starting at 12:00am.
The Benetech GM1020 is ok if you master installing the driver (the device apparently uses a fake FTDI chip and needs an old driver) and upload the settings (doing this the first time is tricky). Beware: Windows 10 eliminates your driver in more recent versions, so it has to be reinstalled from time to time. And it’s getting harder each time.
Last time I did this I had to deinstall the Win driver and install the old driver before Windows could find the new, non-working one. Disconnecting from the net might work, too.
I can help if anyone wants to take this route. The GM1020 is the only budget meter able to store that many data points.
Good call Terry, that is a great idea. This is one of the things they could have improved, but on the other hand, most people probably use it for something else, and not for runtime graphs :)
I could find a driver and software online for the Extech, so I think I'm okay.. not sure if something could cause troubles in the future of course.
Thanks Unheard, thanks for sharing. If anybody goes that route, they know what to do.
I wonder if any of these companies would consider doing a group buy for a luxmeter that could log to USB.
I like the idea !
Note that the Reed Instruments does NOT have to be tethered to a computer. It has a memory card slot - that I remove when done with runtime tests. It also has an optional external power supply that can keep the data logging going for days if necessary (see sample below). I don't think the Extech has either. I wonder how long the Extech can run on one 9V battery? The Reed Instruments uses six AA's.
Just letting you know the pros and cons.
Although I already have 2 log meters, 1 being less than ideal and including some problems (Extech HD400) the SDL400 does a good job at what I want it to do.
But for the sake of other reviewers, a little bump to see if there are any other alternatives.
This looks like an upgraded GM1020?
Benetech GM1030
https://aliexpress.com/item/33010626789.html
I have the UT382… it can be either of these:
-Completely useless because the drivers are impossible to install on anything running windows 7 or newer.
-After installing the drivers on a W10 machine running a virtual instance of windows XP it works great and can easily export values to excel, you can set minimum/maximum value for start/stop, customize data logging interval and real time monitoring. When I was doing reviews I set up a macro to automatically export the values to my runtime graph on excel and after some quick value touch ups I would have a nice runtime graph in less than 5 minutes.
Downsides are it uses a proprietary port so the meter dies with the cable, and it won’t receive power from USB meaning it will drain your batteries QUICK unless you buy one of those Li-Ion to 9V adapter with usb charging from eBay.
Once past the initial setup it is a breeze to use and export the values to your runtime chart. I’d recommend buying one and try to get the drivers sorted out, worst case scenario you get a light meter with no data log function 
I contacted UT asking them to update the drivers (they just need to sign them) but received no response.
Thanks Will! Added a link to your post in the OP
Will the 1030 connect to a PC for uploading data?
No, bluetooth to your phone.
Thanks, so I’ll stick to the 1020.
I'm currently spending some of my spare time on a personal project I've had my sights set on for a while - a standalone runtime test setup based off of the Adafruit TSL2591 light sensor and a Raspberry Pi Zero.
Making it standalone is a bit of a learning experience for someone like myself with little coding skills, but if you want to use it connected to a PC it would be very easy. The sensor and RPi0 together are less than $20, and the rest of the pieces needed to get up and running you probably have in a junk drawer somewhere (microUSB cable, microSD card, some wire).
Edit: If I were going to use this tethered to a PC, I would probably replace the RPi0 with an Arduino Micro or similar.
Arduino is interesting. I did a lot with the Leonardo with its native USB port. You can make it a keyboard to transfer data. And I think there’s a SD shield available. Add LCD and sensor and be done with the hardware.
If you build one and if you make a thread about it, please let me know so I can add that here
I’ll be sure to make a post and link to here if it ever gets to a complete state
Awesome, thanks!
I have a fully functioning proof of concept with a Raspberry Pi Zero W and my TSL2591 sensor. The code is a bit sloppy still, but it works.
Pros:
- Output is fairly clean, no excess noise
- Sensor quality is known unlike using an old Android phone (the one I'm using has a pretty low measurement resolution)
- Includes an IR sensor, though I haven't added code to measure that yet
- Extremely configurable
- Cheap! The Pi Zero W and the sensor are less than $20. I've added some indicating LEDs to my build, and you'll need some wire, a microSD card, and probably a microHDMI adapter for initial setup
Cons:
- Some assembly and soldering is required
- To use this standalone you'll need a basic understanding of ssh and scp tools. If you're using Linux or OS X, it's very easy
If anyone is interested, contact me and I can send a copy of my script to test. If it works I may make it available somewhere in the future.
Interesting, does it work as a stand alone product?
I still have a raspberry doing nothing for over 1,5 year