Hello Jose. We're sorry to hear your HD800 is not functioning properly for you. There are variables in construction that can cause a StudSensor to give false readings and quite often these issues have to do with the environment you’re operating on. There are tried and true techniques we can help you with that can explain why the tool is reacting to density changes that may not be studs and will also promote consistent scanning results. We would be happy to trouble shoot this with you, whatever the problem may be. We stand behind our product. Please contact us through the Zircon website and we’ll figure it out for you. Thank you.