This paper introduces the characteristics, working principle and application of ∑-Δ ADC converter AD7793, including ADC interface circuit design, PCB design and MCU initialization and configuration of AD7793 through SPI interface, and gives the actual measurement of temperature control equipment. result. 2 How the AD7793 chip works disposable vape pen,disposable electronic cigarette,disposable ecigs pen,disposable ecigs stick,disposable e-cigs pen,disposable vape factory,disposable vape pod,disposable vape device,vape pen,vape stick, vape wholesale,wholesale vape,customized dispsoable vape pen,customized vape pen,OEM&ODM disposable ecigs pen,disposable electronic cigarette wholesale, wholesale disposable electronic cigarette,distribute vape pen,vape pen distribute,high quality vape pen,high quality vape pod. Onlyrelx Mini800,High Quality Vape Brand,Onlyrelx Bar,Onlyrelx Ecigs Shenzhen Onlyrelx Technology Co.,Ltd , https://www.onlyrelxtech.com
Temperature control technology has become an important part of industrial, agricultural, scientific research, aerospace and people's lives, especially in the fields of scientific research, aerospace, biomedicine, precision instruments, etc. High, sometimes extremely demanding. The high-precision temperature controller is based on PT1000, MCU, AD7793 and OPA548 as the core chip, featuring high precision, simple structure, small size, good stability and low cost. This paper introduces the characteristics, working principle and application of the AD7793 chip in our high-precision temperature control equipment.
1 AD7793 chip features
The internal block diagram of the AD7793 is shown in Figure 1, which has the following features. 1) High conversion accuracy, 24-bit data output; 2) High chip integration, built-in 24-bit ∑-Δ modulator, buffer, reference voltage source, constant current source, instrumentation amplifier and on-chip digital filter; 3) Three differential analog input channels that can be configured for either buffered or unbuffered mode; 4) Interface circuitry is low and can accept analog inputs directly from strain gauges or sensors. 5) High resolution and low noise, so the requirements for the front-end anti-aliasing filter are greatly reduced. A simple RC low-pass filter is sufficient; 6) The chip has self-calibration and system calibration functions. Eliminate the effects of zero error, full-scale error, and temperature drift. 7) Three-wire SPI interface, through the MCU flexible control and configuration of the AD7793 on-chip registers, to achieve control of the AD7793 chip. 
The AD7793 uses sigma-delta modulation and is highly accurate and accurate compared to dual-integrated ADCs. While in operation, the AD7793 continuously samples the analog input signal at a rate that is controlled by the system clock. The sampled signal is amplified by BUF, PGA, and its output level meets the requirements of the charge-balanced ADC, and then converted into a digital pulse sequence, which is processed by the digital filter to update the data in the data register at a determined rate. The main function of the digital filter is to suppress the serial-mode interference. The digital filter selected by the AD7793 is slightly different at different update rates. The data in the data registers can be read randomly from the SPI interface.
3 AD7793 chip application
The interface circuit of AD7793 is shown as in Fig. 2. According to the measurement accuracy and control accuracy requirements of the system, the RTD sensor PT1000 was selected as the temperature sensor. PT1000 has good long-term stability, good linearity, fast response time, test current within the allowable value range, and small self-heating coefficient to meet the technical requirements of the system. The PT1000 sensor's output change to temperature is generally a microvolt-level weak signal, but the AD7793 has a complete analog front-end function. It integrates a low-noise instrumentation amplifier and can set the gain, so it can directly input the weak signal of the measurement sensor output. The signal passes through the low-pass filter and enters the A/D input of the AD7793. 
RTD sensor PT1000 resistance wiring mainly has three ways: two-wire system, three-wire system and four-wire system. The main difference between them is that the measurement accuracy obtained by different temperature measurement methods is different due to the presence of lead resistance, and should be determined according to the requirements of the application. The accuracy of the two-wire system is low, and the influence of the line resistance cannot be eliminated. The change of the ambient temperature has a great influence on it, and the short-distance can be used; the three-wire system is the mainstream in industrial applications, and one line mainly eliminates the influence of the wire resistance. The balanced bridge is suitable for long distance transmission. The four-wire system is less used, but has high precision and can compensate for errors caused by wires. It is widely used in high-precision measurement. In this device, the four-wire temperature measurement method can completely eliminate the error caused by the lead resistance and meet the requirements of high-precision measurement.