Description
The STPM10 is designed for effective measurement of active, reactive and apparent energy in a power line system using current transformer and shunt sensors. The device can be implemented for peripheral measurement in a microcontroller-based single-phase or poly-phase energy meter. The STPM10 consists of two main sections: analog and digital. The analog part is composed of preamplifier and first-order sigmadelta A/D converter blocks, a band-gap voltage reference and low-drop voltage regulator. The digital part is composed of system control, oscillator, hard-wired DSP and SPI interface. There is also an internal volatile memory, which is controlled through the SPI by means of a dedicated command set. The configured bits are used for configuration and calibration purposes. From a pair of sigma-delta output signals produced by the analog section, the DSP unit computes the amount of active, reactive and apparent energy consumed, as well as the RMS and instantaneous voltage and current values. The results of the computation are available as pulse frequencies and states on the digital outputs of the device, or as data bits in a data stream, which can be read from the device by means of the SPI interface. The system bus interface is also used for temporary programming of bits of internal volatile memory. The STPM10 generates an output signal with a pulse frequency proportional to the energy, and this signal is used in the calibration phase of the energy metering application.