how to calculate reverse value with scale

[Jerson]

output = (reading+130)*10/16
should do it. Where I assume you are reading -130 to +30.

Thus, a reading of -130 will give output = 0
and a reading of +30 will give output = 100

[richard]

or

output = 130-reading
should do it. Where I assume you are reading 130 to 30.

Thus, a reading of 130 will give output = 0
and a reading of 30 will give output = 100

[harryweb]

Ohhh yes yes ! I'm so tired... didn't saw as simple as it is !
Regards