As shown in Fig.  system this measure and electric current, voltage sample two parts.

In the sampling circuit of the electric current, the electric current will produce a pressure drop in the electric current which measure the chip sample the passway while flowing through the manganin alloy shunt, different the intersection of electric current and the intersection of signal and formative the intersection of pressure drop and difference at shunt, measure chip, pass, gather formative the intersection of voltage and signal at shunt, thus has realized the collection of the electric current signal.

What has been gathered is a signal on the line that the voltage is sampled, because the voltage signal is relatively large, the way in which this system design steps down through the resistor network directly realizes the sample of the voltage signal.

This system designs liquid crystal drive control chip that the display of the scheme adopts partly as HT1621, this liquid crystal can drive the liquid crystal segment code of 4*32, can meet the request of showing driving, information such as displayable electric quantity, voltage mean value, electric current mean value, active power.

Consider from the space factor of the products, the power of this system design has been adopted and does not isolate the power, this power supply circuit can offer the electric current of about 60mA.