Changing The Query Based On Value

in the following procedure i want to pass in a value and as a result of the value I want to change the actual body of the query:

example, I pass in the value 'TS2' and I now want my query to see if TS2MIN < 70

i think I am doing it right, but it is throwing an error saying that "Conversion failed when converting the varchar value 'TS2MIN' to data type int."

any idea on what i am doing wrong?

ALTER proc SPU_YearlyTemp 905,'TS2',70,254,2007
@SITEID INT,
@SENSOR VARCHAR(10),
@MIN INT,
@MAX INT,
@YEAR INT


AS
DECLARE @S AS VARCHAR(12)
SET @S=(
SELECT
CASE @SENSOR
WHEN 'TS1' THEN 'TS1MIN'
WHEN 'TS2' THEN 'TS2MIN'
WHEN 'TS3' THEN 'TS3MIN'
WHEN 'TS4' THEN 'TS4MIN'
WHEN 'TS5' THEN 'TS5MIN'
WHEN 'TS6' THEN 'TS6MIN'
WHEN 'TS7' THEN 'TS7MIN'
WHEN 'TS8' THEN 'TS8MIN'
END AS SENSORVALUE)




select top(10)*
into #tempMin
from sitecontroldataarchive
where siteid = @SITEID
and @S < @MIN --this is where the error occurs,
SELECT * FROM #tempMin