儀表校準(zhǔn)程序(Meter Calibration Procedures)

Meter Calibration Procedures
Introduction
Why Calibrate?
A meter fresh out of production will almost certainly expose some error when displaying energy, voltage or current
(and time, if the RTC is used). This error is the sum of the errors introduced by various sources, such as:
?? Voltage divider resistors or voltage transformers (VTs)
?? Current transformers (CTs) and their burden resistors, combined with cable and contact resistance
?? Errors introduced by the phase angle associated with CTs and by the meter power supply
?? The reference voltage of the 71M65XX chip
?? Crystal oscillator
Calibration is the process of trimming the meter so its error becomes minimal. At calibration time, TERIDIAN
energy meter chips typically are given information about the current temperature and characteristics of the
reference voltage over temperature so that they can function within the specified limits at all temperatures.
How Do the TERIDIAN 71M65XX Chips Support Calibration?
Table 1 shows the energy-related calibration factors for a typical three-phase meter (71M6513). When the meter
powers up, it loads these factors from non-volatile memory and writes them to the CE RAM.