Introductive

 

Graph graph of construction of system of 1 number oscillograph

 

By the graph construction of system of 1 number oscillograph is knowable, after signal enters oscillograph through probe system, through ADC is being entered after attenuator and preamplifier are recuperated. Attenuation circuit and amplifier undertake cooperating with working through relay, when adjusting perpendicular resolution but sudden switch is used. The parameter that measures ADC function index has a lot of, for instance a confusion of voices of sampling rate, DNL, INL, letter is compared, effective etc. What the article basically discusses ADC is effective of an index and oscillograph system effective.

 

ADC is effective a definition

 

The sine wave frequency domain that graph 2 ADC collects distributings

 

Of ADC effective index undertakes to sine wave signal FFT spectrum analyses indirect computation to get. Graph 2 it is the frequency domain that commutation of FFT of repass of sampling of AD of sine wave course gets distributinging graph, still put in a lot of noise, harmonic and stray signal besides main sine wave heft.

 

Of ADC effective the definition is:

 

 

In type: 1.76 be ideal ADC quantify noise;

 

6.02 compare for the coefficient Log10 of Log2 translate into.

 

Of oscillograph effective an ENOB

 

ENOB parameter is accepted extensively to be by industry is a kind decide generally the index of bad of actor of performance of system of A/D digital-to-analogue changeover, oscillograph or other digitlization system. All digitlization are put in a variety of errors in the system, these errors can affect the tension that the system gets and “ ideal”Voltage is put in deviation. good to oscillograph system, inside limits of bandwidth of the biggest input, effective digit should mix the system the changeover resolution of A/D is same. In reality, all instruments cannot be ideal, under its normally A/D changes resolution ENOB.

 

By the graph framework of system of 1 number oscillograph pursues knowable, front collects circuit and ADC sampling circuit to have bigger effect to ENOB. When real work, slant buy error, nonlinear error, gain error, random noise and ADC interweave the noise that cause can affect ENOB.

 

Graph curve of 3 oscillograph ENOB

 

ENOB is affected to what concrete signal measures

 

Graph two 4 oscillograph measure same signal

 

The ENOB target of ● oscillograph is good, stray of time error, frequency (cause by joining together error normally) smaller, broadband noise is lower also at the same time;

● ENOB is phasic without the consideration abhorrent ring with frequency lack fidelity etc;

 

What all oscillograph below good case have evenness is phasic ring with frequency curve and boil identically fall means. But cannot find in oscillograph index manual commonly in fact phasic with frequency noisy curve, noisy without consideration frequency also evenness spends same ENOB or phasic abhorrent sex. Pursue the measurement on the 4 oscillograph that showed one inputs signal to differ in two result. The ENOB of two oscillograph is identical, but 1 indication weaveform is close to oscillograph to input signal truely more, and oscillograph 2 indication weaveform are lack fidelity bigger.

 

● ENOB slants without what introduce possibly considering oscillograph buy error.

 

The undee appearance just the same that two oscillograph that have identical ENOB may show, but absolutely voltage slants buy is different. To this, measure oscillograph to be in different slant the background noise below buy perhaps evaluates dc gain index to be able to offer better assessment technique.

 

The measurement of oscillograph ENOB

 

The measurement of oscillograph ENOB needs to consider the following factor:

 

The ENOB that the ENOB of ● test source wants to compare the oscillograph that be measured is big;

● is measured the test result that whether signal is full of oscillograph span to be able to affect ENOB;

● is measured signal frequency and the test result that oscillograph sampling rate can affect ENOB. This are very important, the following requirement must be satisfied in real test. (click in detail examine toward period small letter text: ” must not miss! The benefit from with these FFT true dried foods ” )

 

 

In type:

 

N: Prime number;

N: The analytic check the number of FFT, take 4096 to nod here;

Fs: Oscillograph sampling is led;

Fin: Frequency of the signal that be measured.

 

According to above when, the general train of thought of the measurement of oscillograph ENOB and relevant move are as follows:

 

1, the perpendicular archives with oscillograph appropriate setting, time base archives, store deepness and sampling rate. Sampling rate can be passed adjust time base archives and store deepness change.

 

Graph 5 oscillograph ENOB checks check scheme

 

2, derive datagram expresses.SCV file.

 

Graph 6 oscillograph derive.SCV file

 

3, use EXCEL to undertake to data Fourier alternates, calculate ENOB.

 

Note: Cloud of Baidu of EXCEL pattern plate links:

 

Https://pan.baidu.com/s/1ciUuB3oKfco-10QkR4o3TA

 

Extract a code: X8i5

 

Graph 7 EXCEL handles data to beg solution ENOB

 

Distinct range and frequency are measured below the circumstance of signal, use EXCEL to handle data to beg solution oscillograph ENOB. The result is shown 8 times like the graph, although ZDS2020B Plus uses 8 ADC, as a result of the influence of extent of the signal that be measured, the ENOB that measures actually does not have a law to obtain good position.

 

Graph record sheet of 8 oscillograph ENOB

 

Summary

 

ENOB is one of index that measure oscillograph ADC digital-to-analogue to change property, but taller ENOB is not oscillograph can the requirement of signal of true returning input. This basically depends on measure what signal, and whether can be ENOB affected measure an outcome. In applying actually, the ENOB that can raise oscillograph through the following in order to obtain taller measurement precision:

 

● oscillograph chooses bandwidth to restrict filter, can restrain so interweave the high frequency heft such as noise of sum of errors, obtain taller ENOB thereby;

 

● is in those who measure repeatability or when low frequency signal, the collection that uses average or high resolution mode, can reduce broadband noise so, use these mode integratedly to be able to undertake effectively more high accuracy is measured;

 

● chooses appropriate perpendicular span, general weaveform occupies screen 80%~90% .