High precision voltage source circuit design in process calibrator

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Overview:
Design Purpose In instrument calibration, we hope that the accuracy and resolution of the DC voltage source can be high enough, because this is the key to whether the meter can be calibrated. However, the method of using a single-chip DAC to implement the source is not only costly, but also the performance cannot be guaranteed, especially in terms of dynamic range and resolution. Therefore, it is envisaged to use a two-channel D/A converter, that is, one channel is used to achieve high precision of the voltage source, and the other channel is used to achieve its dynamic range requirement. In this way, while saving costs, the dynamic range and accuracy are also met. After analysis, the LTC1590 with dual 12-bit D/A converter can fully realize the generation of DC voltage source with dynamic range 0~12.5V and resolution of 0.1mV.

The idea of ​​design and implementation is to first generate a basic voltage signal Vstand with a resolution of 0.02mV and a dynamic range of 0~2.5V, and then amplify the basic voltage by 5 times through an amplifying circuit to obtain 0~12.5V. It is a DC voltage of 0.1mV, thus achieving a high-precision voltage source. Therefore, the most central part of the design is the generation of the standard voltage signal Vstand.
Production of standard voltage signal Vstand This design uses a dual 12-bit D/A chip LTC1590CN, as shown in Figure 1.

D/A1 and D/A2 represent two independent D/A converters with a precision of 12 bits in the LTC1590. The reference voltage is based on the 2.5V voltage provided by the AD780.
D/A1 is used to provide the coarse voltage V1. The voltage V2 outputted by D/A2 is diluted 200 times to obtain the fine adjustment voltage. The precision digital potentiometer added in the middle plays the role of adjusting the resolution. Finally, the fine adjustment voltage and the coarse adjustment voltage are added to obtain the standard voltage Vstand.
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