I have recently received nine pieces of IC's marked LM34DZ, however five of them read out in Celsius and are apparently actually LM35DZ. The mismarked pieces all bear the NS logo and a date code 01AD, which National Semiconductor says is an erroneous date code. I have offered to send one of the incorrect parts to NS, but don't know if they really want to see it or not.
In my opinion, the mismarked parts could be knockoffs or they could be the result of an error at NS. Either way, check your LM34DZ parts before you use them. I wasted a fair amount of time troubleshooting a prototype because of this error.
ETA: Just got an e-mail from the woman I talked to at NS. She provided an address and I'll mail a sample of the mismarked part.
In my opinion, the mismarked parts could be knockoffs or they could be the result of an error at NS. Either way, check your LM34DZ parts before you use them. I wasted a fair amount of time troubleshooting a prototype because of this error.
ETA: Just got an e-mail from the woman I talked to at NS. She provided an address and I'll mail a sample of the mismarked part.