A measuring system for measuring signal characteristics on a node is disclosed. The measuring system includes a contact measuring unit including a probe for contacting the node to fetch a signal on the node, an output interface, a plurality of capacitors coupled between the probe and the output interface where a capacitance of each capacitor corresponds to a frequency range, and a protection circuit, of which one terminal coupled between the probe and the output interface and the other terminal coupled to a ground terminal, and a frequency analyzer coupled to the output interface for displaying information of amplitude vs. frequency of a signal outputted from the output interface to measure the signal characteristic on the node.