ACR Y INADVERTENTLY CLRED TO OCCUPIED ALT HAD LTSS FROM ACR X. SYS ERROR.

Narrative

ACR Y WAS GIVEN A DSCNT TO 5000 FT MSL ON INITIAL CONTACT AND TOLD TO EXPECT ILS 35 APCH. THERE WERE 2 OTHER ACFT BEING VECTORED TO THE SAME APCH; AN MTR AND AN SMT. THE OFFICIAL WX; AND THE WX INFO THAT WAS DISPLAYED ON THE SAIDS (SYS ATL INFO DISPLAY SYS) AND XMITTED ON THE HRLY ATIS DID NOT CORRESPOND. THE WX INFO I HAD AT MY DISPOSAL SHOWED A 1000 FT CEILING AND VISIBILITY OF 7 MI WITH LIGHT RAIN. I TOOK A POINT OUT ON AN ACFT LNDG AT AN AUX FIELD (NGW) AND WAS CONCERNED ABOUT SEPARATION BTWN MTR LNDG NGW AND THE MTR MAKING PRACTICE ILS APCHS AT CRP. AT THIS TIME CRP HAD A WIND SHIFT AND CHANGED TO RWYS 13 AND 17. THE OTHER ACFT INVOLVED IN THE SITUATION; ACR X; DEPARTED CRP RWY 35 NBOUND CLBING TO 6000 FT MSL. I RADAR IDENTED ACR X AND DIVERTED MY ATTN BACK TO 2 MTRS. I ASKED THE CTLR WHO SHOULD HAVE BEEN WORKING 1 MTR IF THAT ACFT WAS IN VMC CONDITIONS AT 1500 FT MSL AS OUR WX WAS SHOWING A 1000 FT CEILING AND THE FINAL APCH FOR THE MTR WAS AT 2000 FT OUTSIDE THE APCH GATE. WHILE THE OTHER CTLR TRIED TO OBTAIN THIS INFO I VECTORED ACR Y TO A HDG OF 250 DEGS AND AMENDED HIS ALT TO WHAT I THOUGHT WAS 7000 FT. I WAS READING THE FLT PROGRESS STRIP OF THE DEPARTING ACR X CLBING TO 6000 FT MSL AND INADVERTENTLY ISSUED ACR Y DSCNT TO 6000 FT. THINKING THAT WOULD MAINTAIN VERT SEPARATION. I ISSUED THE TFC TO ACR X AS 1 O'CLOCK 7 MI WBOUND MLG DSNDING TO 7000 FT THINKING THAT IS WHAT I HAD ISSUED. I DIVERTED MY ATTN BACK TO THE 2 MTRS S OF CRP. THE PLT OF ACR Y ASKED IF HE HAD TFC OFF HIS NOSE; AND I ASKED HIM TO VERIFY HE WAS AT 7000 FT MSL. ACR Y SAID HE WAS AT 6000 FT. I ISSUED THE TFC AND AN IMMEDIATE DSCNT TO ACR Y. THE PLT SAID HE HAD VISUAL SEPARATION.