C172 PLT MISSED QNH BY 1 INCH IN N90 CLASS E.

Narrative

I WAS CLRED ON THE WESTCHESTER 1 DEP FROM HPN. CLRED TO MAINTAIN 3000 FT; I INADVERTENTLY CLBED TO 4000 FT. THE CTLR QUESTIONED ME ABOUT THIS; AND I REALIZED WHAT HAD HAPPENED. MY ALTIMETER DID READ 3000 FT; BUT I REALIZED THAT THE WRONG ALTIMETER SETTING HAD BEEN INPUTTED; THUS GIVING ME A FALSE ALTIMETER READING OF 1000 FT TOO LOW. THIS WAS HUMAN ERROR ON MY PART. ON THE GND; I DID MONITOR THE ATIS; AND I DID INPUT THE ALTIMETER SETTING I HEARD; BUT I ENTERED IT INCORRECTLY. I ALSO MISREAD THE ALTIMETER. I THOUGHT IT SHOWED 480 FT; BUT ACTUALLY; IT WAS READING -480 FT. I DID QUESTION THE 480 AS THE KNOWN FIELD ELEVATION WAS 400 FT. I FIGURED THE LCL ALTIMETER SETTING HAD CHANGED AS THE ATIS WAS ALMOST AN HR OLD. I DIDN'T COUNT ON MISREADING THE ALTIMETER; AND I SHOULD HAVE ASKED ATC FOR A NEW ALTIMETER SETTING. UNFORTUNATELY; THE INCORRECTLY INPUTTED ALTIMETER SETTING TOO CLOSELY RESEMBLED THE FIELD ELEVATION IN HUNDREDS. IN RETROSPECT; AFTER TKOF AND ON A DOWNWIND DEP; AS I PASSED THROUGH 1000 FT; I THOUGHT I SEEMED HIGHER ABOVE THE RWY ENVIRONMENT; BUT I DIDN'T MAKE THE CONNECTION. THERE WAS NO WAY I WAS GOING TO PICK UP THE MISTAKE ONCE I WAS AIRBORNE. I FEEL EMBARRASSED AND DEPRESSED ABOUT THIS; AS IT COULD HAVE RESULTED IN SERIOUS INJURY TO MYSELF AND OTHERS. I NEED TO BE MORE CAREFUL ABOUT ROUTINE TASKS LIKE INPUTTING ALTIMETER SETTINGS; AND I NEED TO DOUBLECHK EVERYTHING; WHICH I WILL DO IN THE FUTURE.