A program might be characterised as an instrument. A survey questionnaire could be characterised as an instrument also? Which are the kinds of tools that could be characterised as instruments?
A model, a conceptual framework, a tool that coordinates different elements and carries applicability value in a particular context.
By applying an instrument you assess this environment on specific variables/features that you wish to examine. The instrument yields several indications which you need to evaluate and integrate into your study.
You need to look for applied research methods (this is where instruments belong) within the environment that you are studying. Is it business, social sciences, the arts, information technology, communication? There are countless reliable studies and books authored on different types of evaluation tools/models taking into account their strenghts and weaknesses.