Meaning of 甜-Z (Z is the upper-case English letter)
甜Z is likely the result of imperfect OCR (optical character recognition) for "5Hz". The machine probably sees "5H" as "甜".

It's usually seen in Google's OCR for Chinese patents. If you need to search for original patent text for clarification, you can go to  http://epub.sipo.gov.cn/gjcx.jsp and search the title.