CITS900s4 is the seventh generation of Impedance test system from polar, and typically the most popular model for customers who are new to impedance control. CITS900s4 provides both differential and single ended measurement capability along with 4 channels to provide flexible probe connection. Controlled impedance PCBs are used across a broad range of applications to help ensure high frequency signal integrity. Designers invariably specify these types of PCBs whenever the edge speeds of digital signals are faster than 1ns, or analog signals climb above 300MHz. The characteristic impedance of a PCB trace is determined by the dimensions of the trace and the properties of the PCB material - which can vary from batch to batch. To control trace impedance, PCB manufacturers usually vary trace width to compensate for different batches of PCB material. Historically, they were then forced to use specialist laboratory equipment, such as a time domain reflectometer (TDR), to measure the characteristics of a representative trace etched on the board or a test coupon. This approach was complex, expensive, and far from ideal in a production environment. Many electronics designers - especially those pushing performance boundaries in the defense/aerospace, communications and IT industries - are now taking controlled impedance PCBs a stage further, by using differential signals and balanced traces to improve noise immunity and reduce timing errors on very high speed interconnects. For PCB manufacturers serving these rapidly-growing electronics sectors, verifying the differential impedance of these balanced traces is now a simple task.