用示波器电流探头做小电流测试的方法.ppt

安捷伦科技 市场部资料 2008 Agilent Digital Test Seminar 安捷伦科技 市场部资料 2008 Agilent Digital Test Seminar Page * 用示波器电流探头做小电流测试的方法 Page * 用示波器电流探头做小电流测试的方法 传统的万用表只能做直流电流测试，而且需要断开供电线 示波器加电流探头的方式即可以测试直流电流，也可以测试瞬态的电流变化。而且不需要断开被测供电电路。 一般电流探头进行几十mA以上电流的测试都没有问题，但如何在测更小电流时还能保证测试精度呢？ . For mA level Page * 用示波器电流探头做小电流测试的方法 current probe amplitude accuracy Agilent’s N2780A/1147A Series AC/DC current probe 3% accuracy for 1mA current measurement 6000 Series oscilloscope Oscilloscope noise matters! Agilent大部分电流探头本身都正常可以提供1%的测量精度。在测低至5mA电流时可以提供约3%的精度。但是由于电流探头是把电流量转成电压量用示波器做测量，因此小电流测量时还需要尽可能减少示波器本身的噪声。 Page * 1. 使用能提供尽可能小量程的示波器，并在测量时尽量使用小量程。 (比如最小能到1mV/格的) 2. 把示波器设置成高分辨率模式或平均模式可以大大减少噪声，同时打开示波卡的带宽限制功能。 (20MHz or 25MHz). 降低示波器底噪声的方法 normal mode – 25mApp high res mode – 3mApp 8x averaging mode – 800uApp 用示波器电流探头做小电流测试的方法 Page * 3. 电流探头使用前先做消磁和调零操作。这能够消除残余的磁性，并防止0点的偏差。 用示波器电流探头做小电流测试的方法 Page * 4. 把要测试的电源线在电流探头的磁芯里多绕几圈，这样可以放大被测电流信号。绕的圈数就是电流放大的倍数。 If a conductor is wrapped around the probe 5 times and the scope shows a reading of 25mA, the actual current flow is 25mA divided by 5, or 5mA. 用示波器电流探头做小电流测试的方法 Tackling High-Speed Digital DesignTest * Lets talk about tackling Multi Gigabit Serial Designs today – both whats involved and some new tools and techniques to help make you successful. Tackling High-Speed Digital DesignTest * In recent years, engineers working on mobile phones and other battery-powered devices have demanded higher-sensitivity current measurement to help them ensure the current consumption of their devices is within acceptable limits. Using a clamp-on current probe with an oscilloscope is an easy way to make current measurement that does not necessitate breaking the circuit. But this process gets tricky as the current levels fall into the low milliampere range or below. Tackling High-Speed Digital DesignTest * A modern AC/DC current probe such as Agilent’s N2783A 100-MHz current probe is capable of measuring 5 mA of AC or DC current with approximately 3% accuracy.