PICO Sampling Oscilloscope
Debugging a differential horn cables with Pico's TDR solution
TDR (Time Domain Reflectometry) is popularly used in the areas of R&D, S&I, Manufacture Lines to verify the characteristic impedance and fault of PCB Traces, Cables, Connectors etc. Pico Technology can provide professional TDR instruments in the most cost-efficiency, portable way. PicoScope 9311-15 and 9311-20 are the recommended models with 15GHz/60ps/single-ended and 20GHz/60ps/differential respectively. Also Pico’s fast edge pulse source PG 900 can also work with any PicoScope 9000 model to become a combined TDR solution with the transition time of 40ps. Figure 1 shows the TDR/TDT connecting diagram and PS 9311-20 as well as the PicoSample 3 software UI
Test Setup
Two horns for automotive showed in figure 2 are the DUTs. One of them is good and the other one is bad. Each horn has two differential twisted-pair cables. We want to find out if there’s any possible difference through TDR measurement.
A differential TDR probe is used to connect the cable with PicoScope through two power dividers. Figure 1 up-left part also gives the TDR connection diagram
Test Results
The test results in two green curves of both horns are displayed in Figure 3. The two curves are almost overlapped totally which seems there’s no difference between the good one and bad one. However, if we zoom in the curve around the part of the bump, we will see distinct difference between the two curves as showed in Figure 4. Although the distinction is pretty slight, PS 9311-20 can still distinguish them well due to its excellent performance.
Fast pulse measurement with the most-efficiency high bandwidth oscilloscope – PicoScope 9400 SXRTO
SXRTO – A new type of oscilloscopes
The PicoScope 9400 Series sampler-extended real-time oscilloscopes (SXRTOs) have two or four high-bandwidth(up to 16GHz) 50 Ω input channels with market-leading ADC(up to 12 bits), timing and display resolutions for accurately measuring and visualizing high-speed analog and data signals. They are ideal for capturing pulse and step transitions down to 22 ps, impulse down to 100 ps, and clocks and data eyes to 8 Gb/s (with optional clock recovery). The PicoScope SXRTOs offer random sampling, which can readily analyze high-bandwidth applications that involve repetitive signals or clock-related streams. Unlike other sampling methods, random sampling allows capture of pre-trigger data and does not require a separate clock input. Most importantly, SXRTO provides a much more affordable solution than traditional digital oscilloscope with high bandwidth, high sampling rate and high resolution for high speed applications without compromising the performance. This is why the SXRTO was developed
Test Setup for Fast Laser Pulse Measurement
This example is to use PS 9404 to test a fast laser pulse with the rising time less than 50ps and pulse width less than 200ps. The optical laser pulse will be converted to the electrical pulse for PS 9404 through an O/E adapter. Figure 4 shows one connection case that the DUT doesn’t have a separate trigger signal so that we have to use the signal under test as a trigger signal simultaneously; Figure 5 shows the other connection case that one separate trigger signal can be provided which is input to another channel of the scope.
Test Result
PicoSample 4 software runs in a PC with PS 9404 connected through USB or LAN interface. It’s a professional software which can test general waveform, eye diagram/jitter of high speed serial data. Figure 6 shows the pulse test results including plotting and general measurement parameters like pulse width, rising time, falling time etc
How are the PicoScope 9000 Series Sampling Oscilloscopes different from normal digital storage oscilloscopes?
Digital storage oscilloscopes (DSOs) work by sampling the input signal at regular intervals. The samples are then reconstructed to draw a picture of the signal. The samples must be taken frequently enough to capture the fastest variations in the signal. This technique is called real-time sampling.
A sampling oscilloscope is a special type of oscilloscope that uses a technique called sequential time sampling. This type of sampling is best suited to repetitive waveforms or those that are derived from a regular clock, such as serial data streams, clock waveforms and pulses in digital circuits, semiconductor test patterns, and amplifier pulse-response and rise-time tests. Signals like these tend to have very high bandwidths or high data rates. A sampling scope captures just one sample from one trigger event, typically a single cycle of the waveform or clock, and then repeats the process over a large number of cycles, varying the timing of the sample by a small increment from one sample to the next. The resulting collection of samples is then assembled into a picture of a typical cycle.
Table 1 below shows the main differences between real-time oscilloscopes and sampling oscilloscopes.
