What’s the difference between a Certified Reference Material (CRM), a Standard Reference Material (SRM) and a Reference Material(RM)?
A. These definitions came under considerable debate when ASTM E1724-95 “Standard Guide for Testing and Certification of Metal and Metal Related Reference Materials” was being drafted. Basically a CRM is a standard which is accompanied by a certificate which expresses both the value of the property being measured and an uncertainty. It is generally believed that it must come from a recognized certifying body with demonstrated capability to make these measurements. Some believe that it can only come from a government agency such as NIST. We do not. Alcoa Standards are CRM’s. By definition, an SRM is a certifed reference material produced at a national metrology laboratory such as NIST. An RM is a material that has shown to have a property which is sufficiently homogeneous and established that it can be used to establish a calibration curve or judge the performance of the measurement system. In the absence of a CRM they can be used to assign values to unknowns.
