WinCC 6 I/O field rejects negative inp

I have configurated a float type tag and a I/O field with default limits and decimal data format.
The positive numbers enter correctly, but I cannot input negative numbers, the field reject "+" and "-" characters.
What do I set? thanks in advace.

Go to the Object properties. On the left pane click output/input. Double click Output Format property, and select format with sign for example "s99.99". This is for WinCC 5.1, probably is the same in 6.0.

Well, it works fine. Thankyou