To measure the 431 reference voltage of 25 volts, you first need to connect the test instrument to the test pin of the 431 chip and provide normal power to the power supply pin of the chip.
Next, the actual voltage value of the 431 chip is obtained by adjusting the voltage setting of the test instrument to 25 volts, and then using the measurement function of the test instrument. If the actual measured value differs greatly from the set value, the test instrument needs to be calibrated to ensure the accuracy of the measurement results. The whole process requires rigorous operation and repeated checks to ensure the accuracy of the measurement results.