At all on the contrary a few of th...

At all on the contrary a few of the fastest sweep succeeds the acquisition memory depth and not the maximum sample rate determines the oscilloscope's actual sample rate Peak detection capability, when used correctly, can make up for acquisition memory shortfalls.

One of the principally basic specifications in digital oscilloscopes is the maximum sample rate. Oscilloscope users frequently understand the theory of signal sampling and signal reproduction, still often mistakenly assume that the oscilloscope always samples at its maximum sample rate. In reality, couple specifications need to be considered: the maximum sample rate and the acquisition memory behind the signal sampler. At all further a few of the fastest sweep get ons the acquisition memory depth and not the maximum sample rate determines the oscilloscope's actual sample rate and consequently to what extent accurately the input signal is exhibited on the oscilloscope display. The deeper the acquisition memory, the longer the oscilloscope can sustain a high sampling frequent occurrence on slow time-per-division settings, thus increasing the actual sample rate of the oscilloscope and improving by what means the input signal looks in succession the oscilloscope screen.

The digital oscilloscope's peak detection specification is another oftentimes overlooked specification. This important feature, when used correctly, can make up for acquisition memory shortfalls. In addition, peak detection can be combined with discerning acquisition memory to create unique advantages in digital oscilloscopes.

Digital Oscilloscope Sampling

Basic sampling theory states that for a signal to be faithfully reproduc in sampled form, the sample rate must be greater than twice the highest oftenness present in the signal. This sample rate is known as the Nyquist rate.[1] For an oscilloscope, this means that if the user wants to capture a 100-MHz signal, the sample rate should be at least 200 MSa/s. While the theory states that greater than 2x sampling is sufficient, the practicality is that to propagate the input signal with 2x sampling requires web mathematical functions performed on many samples. Reconstruction is the mete commonly given to the composite mathematical functions performed on the sampled data to interpolate points between the samples. In practice, oscilloscopes that do reconstruction typically have les than alto gether reproduced waveforms because of imperfect application of the mathematical theory,(*) and they may have a deliberate waveform update rate because of the time it takes to do the necessary computations.

One solution to the reconstruction point in dispute is to sample the waveform at a rate long higher then the Nyquist rate. In the limit as sampling becomes continuous, as it is in an analog oscilloscope, the waveform expects "right" and requires no reconstruction. Consequently if the digital oscilloscope can sample fast enough, reconstruction is not necessary. In practice, a digital oscilloscope command of thumb is that 10x oversampling is probably sufficient not to require reconstruction. This regularity dictates that a digital oscilloscope with 100 MHz of bandwidth would require an analog-to-digital converter (ADC) to sample the input signal at 1 GSa/s. In addition, the acquisition memory to retain the samples would have to accept a sample each nanosecond from the ADC. While memories and ADCs in this oftenness range are available, they are typically expensive. To hold fast oscilloscope prices reasonable, oscilloscope manufacturers minimize the amount of fast memory in their oscilloscopes. This outlay minimization has the side validity of dramatically lowering the real sample rate at all however a few of the fastest time-per-division settings.

The sampling theory neared above assumes that the sampler simply gets one chance to "look" at the input signal. Another solution to the reconstruction question is to use repetitive sampling. In repetitive sampling, the waveform is assumed to be periodic and a not many samples are captured each time the oscilloscope descrys the waveform. This allows the oscilloscope to use slower, les expensive memories and analog-to-digital converter while still maintaining highly high effective sample rates across multiple oscilloscope acquisitions. The obvious disadvantage is that if the waveform is not candidly repetitive the oscilloscope waveform may be inaccurately displayed.[2]

Digital Oscilloscope Memory Depth

Now that we understand digital oscilloscope sampling requirements, we can examine for what cause memory depth in oscilloscopes affects the sample rate at a given sweep spe or time-per-division setting. The time window within which a digital oscilloscope can capture a signal is the consequence of the sample period and the duration of the acquisition memory. The acquisition memory is measured by dint of the number of analog-to-digital converter samples it can imprison Typically in digital oscilloscopes the duration of the acquisition memory is fixed, likewise to capture a longer time window (adjust the oscilloscope for a slower time-per-division setting) the sample rate must be reduced