I bought this one to replace another more ornate unit which I'd misplaced. It has taken me a while to master the fiddly nature of this device. I still mess up the process and get the error message. It does seem more stable in terms of its readings reliability than my last unit though. All told, this unit is functional and is priced well but ultimately, has unsatisfying performance.

I carried out two tests 5 minutes apart in different light levels. The first test result was 4.3 and the second 7.3. The Roche is unwilling or unable to provide the light level design paramaters.The only difference was the level of light present at the time. I have since aquitrd a light meter and will conduct more tests.
Easy to use
No technical information relating to design limitations.