I have had a Tech-mate leak detector for about 3 years. I have been able to find r-22 leaks with no problems, but 410 leaks it could not find too well. I was in the market for a new detector until I ran across a youtube video that stated that there was a new sensor available for the tech-mate that was better at finding 410 leaks.
Anyway, I bought the $50 sensor...it's black and not silver like the old one. Bam, it found a leak right away on a system that was leaking 2 lbs a year. Granted, I was unable to find leaks of 4 lbs a year before even when the detector was new. I hope that I can find the 1 lb a year leak and I will be happy.
Just letting you know that the newer black sensor is good so far.