Data items in the DIFFRN_STANDARDS category record details
               about the set of standard reflections used to monitor intensity
               stability during the measurement of diffraction intensities.
               Note that these records describe properties common to the set of
               standard reflections, not the standard reflections themselves.
 
    _diffrn_standards.diffrn_id         's1'
    _diffrn_standards.number            3
    _diffrn_standards.interval_time     120
    _diffrn_standards.decay_%           0