AN2299

An innovative STPM01 approach to calibrate the energy meter: fast digital calibration

Rev2

9/26

2

An innovative STPM01 approach to calibrate the

energy meter: fast digital calibration

The calibration procedure is a key feature among the main meter requirements. In fact, it

impacts directly on accuracy, cost, manufacturability and reliability of the meter.

After the final assembly phase, an energy meter requires a calibration procedure due to

unknown sensitivities of its following blocks:

●

built-in voltage and current sensors

●

oscillator frequency

●

internal reference voltage source

●

analog to digital converters' gain

assuming that the above listed values will not significantly change with environment

temperatures changes and/or by aging.

2.1

Digital calibration procedure: traditional approach

The frequency of the output pulse signal is proportional to active energy.

As shown in Figure 2., the error on the frequency is weighed up by the following

equipments:

●

Precision current and voltage source (Gen)

●

High class precision energy meter (EMp)

●

Meter under calibration (EM)

Figure 2.

Meter calibration set-up

Gen equipment generates the line signals at the same frequency and well known phase

between them. EMp and EM equipments measure the same line signals, but EMp computes

the error by comparing those readings (energy, voltage and current RMS) with the

measured frequency of the EM output pulse signal.

The resulting error has to be minimized acting on some design parameters, known as

calibrators.

Current and voltage

source

Meter under calibration

High class precision

energy meter