通常改变阻值是通过可变电阻人工调节，现在用DS2890通过程序来控制DS2890的阻值，不再用人工的方法，具有准确、简单的效果。-Often change resistance is through the variable resistor artificially adjustment, now DS2890 through with DS2890 procedures to control the resistance, no longer use artificial method, h