一般的专业场强仪电路大多采用专门的宽频带放大器放大后检波，再经过一系列电路送到指示仪表，这种方法的指示性能较高，但电路结构和调整都很复杂，而本人设计的这个简易场强仪是采用先检波后进行直流放大的方案，电路简单，其原理如下： 由天线 TX ；二极管D1 ；电容C1 构成的电路接收到高频信号，经过D2；C2检波后产生的直流电压，再经过BG1；BG2放大后，推动LED发光指示，调节W ，控制BG1的基极电压，进而改变LED的发光强弱，从而达到调节灵敏度的作用。     虽然检波器的灵敏度（检波后输出的直流电压与输入到二极管的高频电压之比）随着高频电压的幅值减小而急速降低，单对于简易场强仪，选择频率特性好的二极管，调节好W，还是可以进行检测的，本场强仪器的频率测试上限取决于二极管D1 ；D2的工作频率。    制作时，按下图所示选择元件即可，图中的"W"可选用带电源开关的线性电位器，这样便于在面板上画出均匀的衰减刻度线，电源可选择6V层叠电池，天线可选用袖珍收音机的小型拉杆天线。制作完成后，应把电路放入屏蔽罩内，以免外界电场干扰，制作成后的外观见下图。    使用方法：使用时，拉出天线，靠近被测电器，旋开W钮，并左右调节，同时观察LED的发光强弱度，结合此时的W钮所在的刻度数即可估测被测电器是否工作及场强大小。使用起来效果不错，简单而且实用！

The General Circuit of professional field intensity meter mostly uses the special wide band amplifier to amplify and detect wave, then passes through a series of circuits to the indicating instrument. This method has high indicating performance, but the circuit structure and adjustment are very complex, the simple field intensity meter designed by me is a simple circuit, which is composed of antenna TX, diode D1, capacitor C1, receiving high frequency signal through D2 After detection, the DC voltage generated by C2 is amplified by BG1, and then the sensitivity of BG2 is adjusted by pushing LED luminescence indicator, adjusting W, controlling the base voltage of BG1. Although the sensitivity of the detector (the ratio of the output DC voltage after detection to the high-frequency voltage input to the diode) decreases rapidly with the decrease of the amplitude of the high-frequency voltage, for simple field strength meters, choose the diode with good frequency characteristics, the upper limit of the frequency test for this field strength instrument depends on the operating frequency of the Diode D1 and D2. When making, select the components as shown in the diagram below. The "W" in the diagram can be selected with a linear potentiometer with a power switch, so as to draw a uniform attenuation scale line on the panel. The power supply can choose a 6V stacked battery, the antenna can be a small tie rod antenna for a pocket radio. After the completion of the production, the circuit should be placed in the shielding case, so as not to interfere with the external electric field, after the appearance of the production as shown in the following figure. Method of use: when in use, pull out the antenna, close to the electric appliance under test, turn the W KNOB, and adjust it left and right, at the same time, observe the LED light intensity, combine the scale number of the W KNOB at this time can estimate whether the electric appliance under test is working and the field intensity. Use Up effect is good, simple and practical!