What does Tokuchu mean in Yokogawa products? [Product print page]

What does Tokuchu mean in Yokogawa products? 

What does Tokuchu mean and what does the /Z denotation signify?

While general specifications contain product information and specifications, Yokogawa also supplies products with additional specifications that are not mentioned in the general specifications. Products with such additional specifications are Tokuchu models. A Tokuchu request is made to specify these additional specifications, and a Tokuchu model is denoted by “/Z” in the model code. TOKUCHU