Research on automatic range conversion method based on PGA

1 Programmable Gain Amplifier

There are two types of programmable gain amplifiers: one is a specially designed PGA circuit, namely the integrated PGA, and the other is composed of other amplifiers plus some control circuits, called a combined PGA.

1.1 Integrated PGA

There are many types of integrated PGA circuits. The PGA102 produced by B-B Corporation in the United States is a high-speed, digitally controlled gain programmable amplifier. It selects the gain of 1, 10 or 100 by the level of pins 1 and 2. Each gain has an independent input terminal and is selected by a multi-way switch. The gain selection of PGA102 is shown in Table 1.

1.2 Combined PGA

The combined PGA is composed of an operational amplifier , an instrument amplifier or an isolation amplifier, plus some additional circuits. Since this article uses an integrated PGA to achieve automatic range conversion , the combined PGA is not described in detail here.

The principle of a digital voltmeter that uses a programmable gain amplifier and a microcomputer to achieve automatic range conversion is shown in Figure 2.

If a dual-integral A/D converter is used , a flowchart can be drawn to realize automatic range conversion by software programming, as shown in Figure 3.

Theory and practice show that the automatic range conversion of intelligent instruments based on PGA and software programming saves the hardware cost of the system and improves the measurement accuracy and reliability of the system. In addition, it is simple to operate, flexible and convenient to use. When the dynamic range of the measured parameter is relatively wide, the effect of using PGA is more significant.