another fix

src/preprocess.py

@@ -63,7 +63,7 @@ class DbOp(object):
                         'unit': res[2]
                     }
                 logger.debug(f"{variable=}")
-            return application
+            return variable
         except Exception as e:
             logger.error(f"Error getting variable: {e}")
             raise VariableNotFoundException(appId, converterId, deviceId, variableId)
@@ -79,7 +79,7 @@ class DbOp(object):
                 with conn.cursor() as cur:
                     cur.execute("""
                         insert into measurement_t (time, application, variable, value, unit) 
-                            values (now(), %(application)s, %(variable)s, %(value)s, %(unit)s
+                            values (now(), %(application)s, %(variable)s, %(value)s, %(unit)s)
                         """,
                         { 
                             'application': measurement['application'],