Non-numeric values in analog I/O points

[djs 169]

I have a system with a FP-3000 controller and a series of TC-120 and RLY-420 modules. At various times I am receiving erros for non-numeric values in some of the analog I/O points. The value, as stated by Ni-FIBUS is "-1.#IND".
Does any one know what this is? Also once this value appears, It is impossible to get rid of it. The function must be completely deleted and re made from scratch.

[S.G.]

Some general suggestions:
1. Settings of Function Blocks do not match the real input values, such as type mismatch. You need to verify the value data and type.
2. Invalid Scaling settings, the units of parameters between connecting function blocks may not match. Please check the block input and output.