GW Instek MSO-2102EA 100 MHz, 2-Ch. Digital Storage Oscilloscope
100 MHz bandwidth
Equipped with a 16-Channel Logic Analyzer and a dual channel 25 MHz arbitrary waveform generator
Real time sample rate for each channel is 1GSa/s
Free Frequency Response Analyzer Software (Download from manufacture website only)
Maximum 10M memory depth and VPO waveform display technology
Waveform update rate up to 120,000 wfms/s
8" WVGA TFT LCD screen display
Maximum 1M FFT provides higher frequency domain resolution measurements
High Pass, Low Pass and Band Pass Filter Functions
29,000 segmented memory sections and waveform search function
I2C/SPI/UART/CAN/LIN serial bus trigger and decoding functions
Data log function is able to track signal changes up to 100 hours
Network storage function
How to choose oscilloscope?
You should know what you plan to use the oscilloscope to observe. What is the special feature of the signal you want to capture? Does your signal have complex characteristics? Is your signal repeat signal or single signal? What is the bandwidth, or rise time, of the signal transition you want to measure? What signal characteristics do you intend to use to trigger short pulses, pulse widths, narrow pulses, etc.? How many signals are you going to display at the same time? Analog or digital?
In all, the traditional view thinks that the analog oscilloscope has the familiar panel control, the price is low, therefore always thinks that the analog oscilloscope "USES conveniently". However, with the increasing speed and price of A/D converter year by year, as well as the increasing measuring capacity and virtually unlimited functions of digital oscilloscope, digital oscilloscope has become the leader.
How is the bandwidth?
Bandwidth is generally defined as the frequency when the amplitude of sinusoidal input signal attenuates to -3db, that is, 70.7%. Bandwidth determines the basic measuring ability of oscilloscope to signal. With the increase of the signal frequency, the oscilloscope's ability to display the signal accurately will decline, if there is not enough bandwidth, the oscilloscope will not be able to distinguish the high-frequency change. The amplitude will be distorted, the edges will disappear, and the details will be lost. Without sufficient bandwidth, all the properties of the signal obtained, such as ringing and singing, are meaningless.
A rule of thumb for determining the bandwidth effectiveness of the oscilloscope you need is the "5x rule"; Multiply the highest frequency component of the signal you want to measure by 5. This will give you an accuracy of more than 2% in your measurements
In some applications, you do not know the bandwidth of the signal you are interested in, but you know the fastest rise time, most digital oscilloscopes use the following formula to calculate the associated bandwidth and the rise time of the instrument: bandwidth = 0.35 ÷ the fastest rise time of the signal.
There are too kinds of bandwidths: repeat (or equivalent time) bandwidth and real time (or single time ) bandwidth. Repeat bandwidth is only applicable for repeat signals to display comes from sampling during multiple signal acquisition. Real-time bandwidth is the highest frequency that can be captured in a single sample of oscilloscope, and the requirements are quite demanding when the captured events do not often occur. Real-time bandwidth is associated with sampling rates.
Since wider bandwidth tends to mean higher prices, evaluate the frequency components of the signals you normally look at against your budget.
How is the sampling rate?
Defined as sampling times per second (Sa/s), the frequency of signal sampling by exponential oscilloscope. The higher the sampling rate of the oscilloscope, the higher the resolution and clarity of the waveform displayed, and the lower the probability of important information and events being lost.
The minimum sampling rate becomes important if the slow signal over a long time range is observed. In order to maintain a fixed waveform number in the displayed waveform record, the horizontal control button needs to be adjusted, and the displayed sampling rate will also change with the adjustment of the horizontal control button.
How to calculate sampling rate? Measuring method depends on the waveform measured and the signal reconstruction method adopted by oscilloscope.
To reproduce the signal accurately and avoid confusion, the Nyquist theorem states that the sampling rate of the signal must be no less than twice its highest frequency component. However, the premise of this theorem is based on infinitely long and continuous signals. Since no oscilloscope can provide a record length of infinite time and, by definition, low-frequency interference is discontinuous, sampling rates of twice the highest frequency components are usually insufficient.
In fact, the accurate reproduction of signal depends on its sampling rate and the interpolation method used in the gap of signal sampling points. Some oscilloscope will provide following choice to operator: sinusoidal interpolation method for measuring sinusoidal signal, and linear interpolation method for measuring rectangular wave, pulse and other signal types.
There is a useful rule of thumb for comparing sample rates and signal bandwidths: if the oscilloscope you are looking at has interpolation (filtered to regenerate between sampling points), the ratio (sampling rate/signal bandwidth) should be at least 4∶1. Without sine interpolation, the ratio of 10∶1 should be adopted.
How fast does the screen refresh?
All oscilloscopes flash. That is to say, the oscilloscope captures the signal at a certain number of times per second, and the measurement between these measuring points is no longer carried out. This is the waveform capture rate, also known as screen refresh rate, expressed as the number of waves per second (WFMS /s). Sampling rate represents the frequency of input signal sampled by oscilloscope in a waveform or period.Waveform acquisition rate refers to the oscilloscope acquisition waveform speed. Waveform acquisition rate depends on the type and performance level of oscilloscope, and has a large range of changes. The oscilloscope with high wave acquisition rate will provide more important signal characteristics and greatly increase the probability of the oscilloscope to quickly capture instantaneous abnormal conditions, such as jitter, short pulse, low frequency interference and instantaneous error.
Digital storage oscilloscope (DSO) can capture 10 to 5,000 waveforms per second using a serial processing structure. DPO digital fluorescence oscilloscope USES parallel processing structure, can provide higher waveform capture rate, some up to millions of waves per second, greatly improve the possibility of intermittent capture and difficult to capture events, and allow you to find the signal problems faster.
What is the storage depth?
Storage depth is a measure of how many sampling points an oscilloscope can store. If you need to capture a pulse string continuously, you need the oscilloscope to have enough memory to capture the entire event. The required storage depth, also known as record length, can be calculated by dividing the length of time to be captured by the sampling speed required to accurately reproduce the signal.
Capturing the effective trigger of the signal in the right position can usually reduce the storage capacity of the oscilloscope.
Storage depth is closely related to sampling speed. The depth of storage you need depends on the total time span to be measured and the required time resolution.
Modern oscilloscopes allow users to select record lengths to optimize the details of some operations.Analysis of a very stable sinusoidal signal requires only 500 points of record length;But to parse a complex stream of digital data, you need a million points or more of record length.
What kind of trigger do you need?
The trigger of the oscilloscope can synchronize the horizontal scanning of the signal at the right position, which determines whether the signal characteristic is clear or not. Trigger control buttons stabilize repeated waveforms and capture single waveforms.
Most users of universal oscilloscopes only use edge triggering, and you may find it useful to have other triggering capabilities in some applications. Especially for the fault search of new design products.Advanced triggering allows the event of interest to be isolated, making the most efficient use of sampling speed and storage depth.
Today there are many oscilloscopes with advanced triggering capabilities: you can trigger based on pulses defined by amplitude (such as short pulses), time-limited pulses (pulse width, narrow pulse, conversion rate, build/hold time), and pulses (logical trigger) described by logical state or graph.The combination of extended and regular triggering functions also helps to display video and other hard-to-catch signals, so advanced triggering capabilities provide a great deal of flexibility in setting up the test process and greatly simplify the job.
How many channels do you need?
The number of channels you need depends on your application. For the general economic fault - finding applications, the need is a dual - channel oscilloscope. However, if you want to observe the interrelationship of several analog signals, you will need a 4-channel oscilloscope. Many engineers working in analog and digital systems are also considering 4-channel oscilloscopes.A newer option, called a mixed-signal oscilloscope, combines the logic analyzer's channel counting and triggering capabilities with the oscilloscope's higher resolution into a single instrument with a time-dependent display.
Main classification and and characteristics of oscilloscopes’ probes
The passive probe is made of wires and connectors and includes resistors and capacitors when compensation or attenuation is required. There are no active devices (transistors or amplifiers) in the probe, so no power supply is required for the probe. Passive probes are generally the strongest and most economical probes, and they are not only easy to use, but also widely used.
1.2 High resistance passive voltage probe
Actually, voltage probes are widely used among which high resistance passive probes are the most. Passive voltage probes provide attenuation 1x, 10x and 100x for different voltages. During these passive probes, 10x passive probes are most widely used probes. For applications where the signal amplitude is 1 v peak-to-peak or lower, a 1 x probe may be appropriate or even necessary. In application where low - and medium-amplitude signals are mixed (tens of millivolts to tens of volts), the switchable 1 x /10 x probe is much more convenient. However, the switchable 1 /10 probe is essentially two different probes in the same product, with not only different attenuation coefficients, but also different bandwidth, rise time and impedance (R and C) characteristics. Therefore, these probes do not exactly match the input of the oscilloscope and do not provide the optimal performance achieved by the standard 10 x probe.
1.3 Low resistance passive voltage probes
Bandwidth of most high resistance passive probes range from less than 100MHZ to 500 MHZ or more than. However, frequency characteristics of low resistance passive probes(also called 50 Ohm probe, Zo probe, voltage divider probe) are very good, adopting probe matching coaxial cable, bandwidth could reach 10GHZ and 100 psec or faster rise time. The probe is designed for use in 50 ohm environments such as high-speed equipment verification, microwave communications and time domain reflectometers (TDR).
1.4 Passive high voltage probes
High voltage is one relative concept. We can define a high voltage as any voltage that exceeds the voltage that a typical generic 10 x passive probe can safely handle. High voltage probes require great dielectric strength to ensure safety of user and probes.
2. Active voltage probe
2.1 Active probes
Active probes include or depends on active circuits, such as crystal valve. Most commonly, an active device is a field effect transistor (FET) that provides very low input capacitance, which leads to high input impedance over a wider frequency band.
2.2 Passive FET probe
Bandwidth of passive FET probes are usually during 500MHZ to 4GHZ. The high input impedance of an active FET probe allows measurements to be made at test points with unknown impedance, and the risk of a load effect is much lower. In addition, because low capacitance reduces the effect of ground wires, longer ground wires can be used.
Active FET probes have no passive probe voltage range. The linear dynamic range of active probe is generally between ±0.6v and ±10V.
2.3 Active differential probe
Differential signals are signals that refer to one another rather than to ground. The differential probe can measure the signal of the floating device, which is essentially composed of two symmetrical voltage probes with good insulation and high impedance to the location, respectively. The differential probe provides a high common mode rejection ratio (CMRR) over a wider frequency range.
3. Current probe
In principle, the current value can be easily obtained by dividing the voltage measured by the impedance measured by a voltage probe. However, in practice this measurement introduces a large error, so generally do not use voltage conversion current method. The current probe can accurately measure the current waveform. The method is to use the current transformer input, the signal current magnetic flux is transformed into voltage by the mutual inductance transformer, and then amplified by the amplifier inside the probe and sent to the oscilloscope.
3.1 Ac current probe
The alternating current in the transformer will generate electric field and induce voltage with the change of current direction. The ac current probe is a passive device that requires no external power supply.
3.2 DC current probe
Conventional current probes can only measure ac and ac signals, because a stable dc current cannot induce current in a transformer. However, using the hall effect, a semiconductor device with a bias current will generate a voltage corresponding to the direct current field. Therefore, the dc current probe is an active device that needs external power supply.
So current probes are basically divided into two kinds: AC current probes and AC/DC current probes. AC current probes are usually passive probes and AC/DC active probes.
4. Logic probe
When observing and analyzing the analog characteristics of digital waveform with oscilloscope, logic probe is needed. In order to isolate the exact cause, digital designers usually need to check the specific data pulse that occurs under specific logic conditions, which requires logic trigger function.
5. Other probes
Because the application scope of oscilloscope is very wide, so in addition to the above types of probes there are a variety of special probes, these professional probes according to the different front-end sensors and have different functions, we introduce two of them below, only for readers to understand.
Photoelectric probe is a combination of common voltage probe and photoelectric conversion device in principle, which can directly measure optical device and optical signal transmitted by optical fiber.
Temperature probe is a combination of common voltage probe and temperature sensor, which can directly measure the temperature of an object.Temperature probe is a kind of sensor probe. Various sensor probes and oscilloscopes can be combined to measure a variety of physical quantities.