IEC 61000 vs IEC 61326? Electromagnetic compatibility(EMC)
IEC 61000 are "basic" standards which contains the measurement techniques. IEC 61326 is a Product Family standard which contains conditions, limits and performance criteria for equipment for measurement, control and lab use.

Standards are applicable in this order 


Product Standard, if applicable, otherwise
Product Family Standard, if applicable, otherwise 
Generic Standard


61326 is mentioned in this hierarchy here: 


  The structure of EMC standards
  
  EMC requirements are specified in a vast number of standard documents
  issued by various committees and organizations. The documents are
  organized as follows:
  
  Basic standards: Describe the phenomenon, characterize the test
  equipment and give guidance how tests shall be performed and
  documented. Basic standards like IEC 61000-4-x form the lowest level
  in standard's hierarchy.
  
  Generic standards: Specify test levels for a certain range of
  application, referring to the Basic Standards for general information.
  Generic standards give minimum requirements, e.g. for CE Mark (EN
  61000-6-1). Generic Standards stand above the Basic standards.
  
  Product Family standards: Are used where exist for a certain category
  of products. They specify test levels and performance criteria. EN
  61326, for instance, forms such a Product Family standard dealing with
  the EMC requirements of equipment for measurement, control laboratory
  use.
  
  Product standards: Are the most preferred standards as they give
  strict requirements for a certain product. EN 61800-3 for instance is
  a Product Standard for adjustable speed electrical power drive
  systems. Apart from the requirements for EMC this standard also
  defines special test procedures. Product Standards form the highest
  level in standard's hierarchy.


Source: EM Test

but all can refer to the basic standards for the measurement techniques.