2600S-901-01 Rev. C / January 2008 Return to Section Topics 12-7
Series 2600 System SourceMeter® Instruments Reference Manual Section 12: Instrument Control Library
Time and date values
Time and date values are represented as a number of seconds since some base. There are three
time bases:
1. UTC 12:00 am Jan 1 1970.
2. When the Series 2600 is powered on.
3. Time referenced to an event, such as the first reading stored in a reading buffer.
Time can be represented as the number of seconds since UTC 12:00 am on January 1, 1970. The
commands that utilize this format are commands that require an absolute time reference such as
setting the calibration date.
Time can also be represented as the number of seconds since the unit was powered on. The
os.clock() function returns values in this format.
Representing time as a number of seconds will be referred to as “standard time format.” Note that
because numbers are floating point numbers, the precision of date/time values will decrease the
farther the elapsed time gets from its reference base. This decrease in precision is approximately
0.06ppm of the total elapsed time. This precision is generally more accurate than the time base of
the instrument and should not present any problems. It is worth noting, however, because you can
directly see the affects as compared to the less obvious time-base drift.
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