12 Oscilloscope Functions You Must Know

The oscilloscope is a widely used test instrument. How many of the following 12 functions do you know?

1. Protocol decoding

The original oscilloscope was just a simple waveform display and data measurement. If we want to get the deeper meaning of the protocol waveform, we need to analyze it section by section.

For example, if we observe the IIC protocol, we have a clock signal and a data signal. We need to convert the clock and data signals one by one, and then "translate" them into the form we need, and then correspond them to the corresponding physical quantity. This is not only labor-intensive and inefficient, but also prone to errors.

The current protocol decoding directly decodes the waveform data and presents it in the form of hexadecimal, decimal or characters, eliminating the conversion process for engineers and greatly speeding up development efficiency. Figure 3 shows the decoding of a CAN protocol, which can be done in one step.

CAN protocol decoding under dual ZOOM

2. Network Analyzer

Usually we need a lot of measurement practice to achieve accurate amplitude and phase parameter measurement and avoid major errors. Due to the uncertainty of RF instrument measurement, small errors are likely to be ignored. As a precision instrument, the network analyzer can measure extremely small errors.

Network analyzers can be divided into two types: scalar (only contains amplitude information) and vector (containing amplitude and phase information). Scalar analyzers were once widely used due to their simple structure and low cost. Vector analyzers can provide better error correction and more complex measurement capabilities. With the advancement of technology, the improvement of integration and computing efficiency, and the reduction of costs, the use of vector network analyzers is becoming more and more popular.

Electronic networks are measured in a similar way to optical devices. The network analyzer generates a sinusoidal signal, usually a swept frequency signal. As the DUT responds, it transmits and reflects the incident signal. The strength of the transmitted and reflected signals usually varies with the frequency of the incident signal.

The response of the DUT to an incident signal is an indication of the performance of the DUT as well as discontinuities in the characteristic impedance of the system. For example, a bandpass filter has a high reflection coefficient outside the band and a high transmission coefficient inside the band. If the DUT deviates slightly from the characteristic impedance, it will cause an impedance mismatch and generate additional undesired response signals. Our goal is to establish an accurate measurement method to measure the DUT response while minimizing or eliminating uncertainty.

3. Play the movie on the DVD drive

What else can you do with a large LCD screen? Sure, you can watch a tutorial on signal integrity analysis on your oscilloscope, but even better, you can watch recent movies (no 3D video, though).

4. Filtering

Oscilloscopes generally have a bandwidth limit of 20MHz, which is a hardware filter. Some oscilloscopes also support software filters with adjustable cutoff frequencies. The ZDS2024Plus can be infinitely adjusted from 100Hz to 100MHz.

TDS5000 can perform 20MHz and 150MHz low-pass filtering, and can also perform a digital low-pass filtering called high-resolution acquisition. In this mode, the vertical resolution of the sampling point can be increased from 8 bits to 12 bits. The above system can output a sine wave waveform similar to a signal such as PWM according to the trend of pulse width change.

5. Broadband radar test

Agilent's Infiniium oscilloscope combined with 89601 vector signal analysis software forms a wideband radar analyzer that can perform a variety of radar measurements and analyses from pulse, baseband, intermediate frequency and RF/microwave angles, including:

1. Radar pulse parameter test, such as rise time, pulse width and stability, pulse interval and stability, etc.;

2. Test and analysis of radar pulse jitter, clock, PLL jitter, etc.;

3. Radar intra-pulse initial phase test;

4. Vector analysis of radar signals;

5. Radar receiver I/Q channel consistency test;

6. Wideband test and online test of various radar amplifiers, etc.

Infiniium oscilloscopes have a variety of options, including 600MHz to 1GHz bandwidth (4GSa/s sampling rate), 2GHz to 7GHz bandwidth (20GSa/s sampling rate), and 10GHz to 13GHz bandwidth (40GSa/s sampling rate). Combined with 89601 vector signal analysis software, the analysis bandwidth can reach up to 13GHz, making it a true broadband radar analyzer.

The signal enters the oscilloscope through a cable or an oscilloscope probe (online testing can be performed using an oscilloscope probe). Inside the oscilloscope, the signal first passes through an attenuator and a preamplifier, and then is coupled to the ADC for digitization. The digitized waveform can be displayed directly, or converted into I and Q signals through I/Q conversion and digital filtering (I and Q signals can be displayed directly); the time domain data is then transformed by FFT to obtain frequency domain data; the time domain data is demodulated for demodulation analysis, such as displaying a constellation diagram or code domain data. As can be seen from the figure, the broadband radar analyzer is actually a data acquisition and data processing process that combines hardware and software. Because the ADC has a high enough real-time sampling rate (up to 40GSa/s), the broadband radar analyzer has a high enough analysis bandwidth, up to 13GHz.

6. Improve vertical resolution

Most oscilloscopes have an A/D resolution of 8 bits. Using different acquisition modes, the vertical resolution can be increased by averaging adjacent samples as described below. So how much resolution can be increased by averaging and using high resolution mode? Theoretically, the increase is 0.5Log2N, where N is the number of adjacent samples averaged.

In practice, the 2-byte memory depth limits this increase. Two bytes are 16 bits. One of these bits is reserved as a sign bit, and the remaining 15 bits are used for the data value. Rounding errors make the 14th and 15th bits random values, making the actual limit 13 bits. Therefore, the improvement starts at about six significant bits and increases to about 13 bits with high oversampling.

Improve vertical resolution