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土壤的湿度是否恰当,对于农业科学种植与实验有着密切的关系。附图所示电路能够较好地测试出土壤的湿度是否符合要求,简单适用。 电路的工作原理:电源E经电阻R_1限流,由二极管V_1、V_2箝位于1.2V左右,为三极管V_3提供稳定的工作电压。当A、B两探头插入土壤中时,A、B之间具有一定的电阻R_(AB),如果土壤湿度大,R_(AB)小,V_3导通程度增强,微安表指示数值大;反之,土壤湿度小,微安表指示数值小,以此就能判断出土壤的湿度情况。开关S合“2”时,可检查工作电压及微安表是否正常。
Soil moisture is appropriate for the agricultural science planting and experiment has a close relationship. The circuit shown in the figure can better test whether the soil humidity meets the requirements and is simple and suitable. The working principle of the circuit: The power supply E is limited by the resistor R_1, and clamped by the diodes V_1 and V_2 at about 1.2V to provide a stable operating voltage for the transistor V_3. When A and B are inserted into the soil, there is a certain resistance R_ (AB) between A and B. If the soil moisture is high, R_ (AB) is small and V_3 is conductive, the microampere meter indicates a large value. On the contrary , Soil moisture is small, microamperes table indicates a small value, in order to be able to determine the soil moisture conditions. Switch S together “2”, can check the working voltage and microampere meter is normal.