SEA LCL CTLR EXPERIENCED OPERROR ON FINAL INVOLVING WAKE TURB SEPARATION.

Narrative

I WAS WORKING THE LCL CTL POS ON DAY X. THE FINAL CTLR ON POS AT THE TIME WAS VECTORING ACFT INBOUND WITH MINIMUM SEPARATION. JUST PRIOR TO THE ERROR I HAD AN ACFT FOLLOWING TOO CLOSE TO A HVY JET. WHEN I WAS IN COM WITH THE FOLLOWING ACFT I ASKED IF HE SAW THE PRECEDING ACFT IN SIGHT; HE SAID HE DID AND I WAS ABLE TO ALLOW THE ACFT TO CONTINUE HIS APCH. 2 ACFT LATER I HAD A B767 FOLLOWED BY AN MD80. LOOKING AT MY STARS DISPLAY I DETERMINED THAT I HAD ENOUGH SPACING AND COMPARABLE SPDS TO ALLOW THE MD80 TO CONTINUE THE APCH. IN MY OPINION I HAD THE REQUIRED SEPARATION AT ALL TIMES. AN AUDIT WAS PERFORMED ON THE DATE ABOVE. IT WAS DETERMINED BY ELECTRONIC MEANS THAT I DID NOT HAVE THE REQUIRED SEPARATION AND I WAS ACCESSED AN OPERROR BASED ON THE AUDIT. IT IS MY UNDERSTANDING THAT THE PEOPLE WHO DO THESE AUDITS USE A PROGRAM THAT TRACKS SPACING AT ALL TIMES THROUGHOUT AN ACFT'S FLT. IT SEEMS TO ME THAT IF WE AS AIR TFC CTLRS ARE BEING HELD TO THIS TYPE OF PRECISION WE SHOULD HAVE THE EQUIP THAT WILL ALLOW US TO MAINTAIN WHAT IS REQUIRED OF US. THE SEPARATION WAS 4.72 MI WHEN THE HVY JET WAS JUST INSIDE OF 1 MI FINAL. THAT MEANS THAT; ACCORDING TO MGMNT; I SHOULD HAVE BEEN ABLE TO TELL THE DIFFERENCE BTWN 5 MI AND 4.72 MI ON MY STARS SCOPE. I DO NOT KNOW IF THOSE WHO ARE READING THIS HAVE EVER LOOKED AT A STARS SCOPE BUT THEY DO NOT PROVIDE YOU WITH ENOUGH RESOLUTION TO DETERMINE THIS AMOUNT OF DIFFERENCE; .28 MI!