Learning Lab

A real number a has a unique nonnegative square root, which is called principal square root. It is denoted by √ symbol, where √ is called the radical sign or radix. For example, the principal square root of 16 is 4, which is denoted by √16 = 4, because 16 = 4×4. The number whose square root is calculated is known as the radicand. The radicand is the number or expression underneath the radical sign, in this example number is 16.

The absolute value of a number is its distance from zero on the number line. Absolute value of -5 is 5, thus the absolute value of a number refers to the magnitude of the number irrespective of its sign.

Negation of a number is calculated by multiplying the number with ‘-1’. When you calculate the negation of a signal, all the values of that signal are multiplied with ‘-1’ and signal is generated using that calculated data.
Negation function can be expressed as:
Negation of number x = (-1) * x

Reciprocal function is used to find the multiplicative inverse of that signal. Reciprocal function calculates the reciprocal of the signal values and plots the signal graph using those calculated values. Reciprocal of a number is calculated by dividing 1 by that number. So, it can be expressed as:
Reciprocal of a number x = 1/x = x-1

This function is used to convert data from Linear (Pascal, g, m/sec etc) to dB. It is mostly used in the field of acoustic but any data can be converted into dB with respect to a reference value. For noise data, dB reference is taken as 20E-6 and for all other, it is taken as 1. It is a logarithmic scale. Linear to dB conversion is performed using the formula
Output dB = 20 * log10(Input Data Values / Reference)
This function is used to convert data from decibel to linear. Decibel is mostly used in the field of acoustic but any dB data can be converted into linear with its reference. For noise data, dB reference is taken as 20E-6 and for all others, it is taken as 1. It is a logarithmic scale. Decibel to linear conversion module requires signal unit as input which is used for selecting the reference. The calculation is done using the formula Output Linear = Reference * 10(dB/ 20)
An antilogarithm(antilog) is the inverse of the log function. It is a mathematical function. The basic equation for antilog is: If Logb Y=X then Y= antilog X In ASI Datalab, the user can select whether base 10 or base e to be used for antilog of a signal.

Logarithm, the exponent or power to which a base must be raised to yield a given number. Expressed mathematically, x is the logarithm of n to the base b if bx = n, where one can write x = logb n. So, log function can be expressed as

logb(x) = y
by = x

The logarithm to base 10 (that is b = 10) is called the common logarithm
The logarithm to base e (that is b = e) is called the natural algorithm

Concatenate function is used for joining 2 signals, the 2nd signal will be joint at the end of the 1st signal. This function is useful when data is acquired in different dataset or time and user wants to concatenate all data in the single dataset at the end of the test.
Concatenate function is used for joining 2 signals, the 2nd signal will be joint at the end of the 1st signal. This function is useful when data is acquired in different dataset or time and user wants to concatenate all data in the single dataset at the end of the test.

Reverse function is used to create a mirror image of the signal. The values from the beginning and from the last are interchanged successively to produce the reverse of the signal. For example, first value and last value are interchanged, second value and Second last value are interchanged, and so on.

Workzone function is used to cut/trim a certain region of the signal so that the user can visualize or analyze that particular region of the signal only. A user can give the initial and final time of the region you want to create workzone. This function can be used for any type of signal.

A square wave is a combination of several sine waveform whose amplitude changes from maximum to minimum instantly. Square waveform has all even harmonic frequencies.

The sawtooth wave is a kind of non-sinusoidal waveform. It is so named based on its resemblance to the teeth of a plain-toothed saw with a zero-rake angle. The convention is that a sawtooth wave ramps upward and then sharply drops.

A sine swept signal is a sinusoidal waveform whose frequency varies with time. Thus, the peaks in this signal will get closer together or further apart as time goes on. By applying a sine swept to a system, we can measure the system’s response to sinusoids of various frequencies. System’s response to other inputs can be predicted using these measured responses.

A sine or sinusoidal waveform is a mathematical curve that describes a smooth periodic oscillation. Its most basic form as a function of time (t) is:
 y(t) = A sin(ωt + φ)
where:
A = Amplitude
ω=2πf – angular frequency
t = time
φ = Phase

Integration is the inverse of Differentiation. Integration is a mathematical function which represents area under a curve. Given a function f of a real variable x and an interval [a,b]of the real line…

Differentiation is a calculus function which is used to calculate the rate of change of parameters with respect to another parameter. For example, the user can find the acceleration of a vehicle by differentiating velocity with respect to time. The operand used for differentiation is called a derivative.
“Change Signal Unit Label” function is used to change the Unit label of the signal. It is used when the data is converted from one unit to another, but the label is not changed. For example, when acquired voltage is calibrated using sensitivity and offset values the signal unit shows as Voltage, which need to change as per engineering unit of sensitivity example g or m/sec^2 in case of acceleration data. User can select appropriate unit from the drop-down list that appears when you select the function.

What is "Change Start Time" function and how it can be performed in ASI Datalab?

Change Start Time function is used to change the first x axis value of time domain signal without changing sampling rate and total length of signal. It is useful when some part of whole signal is used for analysis or work zone is applied to dataset. It is also useful for x-axis alignment with another signal acquired at different time.

What is 'revert a signal to volt' function and how it can be performed in ASI Datalab?

Any signal with engineering unit can be converted into volts using this function with the help of values for offset and sensitivity of transducer used during acquisition. Sometimes it is required to see voltage data in place of engineering unit for better interpretation.

What is calibration and how it can be performed in ASI Datalab?

Calibration is used when you have acquired the data from transducer without using its sensitivity in terms of engineering unit and voltage data acquired. Sometimes it happens that during testing we forget to enter the sensitivity of the transducer. This function is helpful to convert data from voltage to an engineering unit like g, m/sec, Newton etc.

What is resampling and how to resample a signal in ASI Datalab?

Resampling function is used when you want either more no of samples often called up-sampling or less no of samples called down-sampling in the signal than the current. Resampling changes the sampling rate (Samples / Sec) of a signal and total no of point keeping the total duration of data same.

What is isolation and how to calculate isolation in ASI Datalab?

Isolation is the ratio of difference between input (Reference/Excitation) and output (Response) to Input (Reference/Excitation). Generally, it means reduction. It can be represented in percentage (%) or dB.

What is a Band-stop Filter (Butterworth Filter) and how to perform it in ASI Datalab?

Band Stop Filters (BSF)can be used to filter out certain frequencies that lie outside a particular band or range (lower and higher cutoff) of frequencies. This filter is combination of lowpass and highpass filter.

What is Transmissibility and how to calculate it in ASI Datalab?

Transmissibility is the ratio of output (Response) to input (Reference/Excitation). Generally, it means amplification & maximum amplification occurs when natural frequency and excitation/reference frequency of the system coincide. It measures the effectiveness of vibration isolating system. Lower transmissibility represents better isolation.

What is a High-pass Filter (Butterworth Filter) and how to perform it in ASI Datalab?

High-pass filter is an electronic filter which passes frequencies higher to cutoff frequencies and attenuate the lower frequencies. It has many uses like removing DC offset, radio frequencies etc

What is a Low-pass Filter (Butterworth Filter) and how to perform it in ASI Datalab?

Low-pass filter is an electronic filter which passes frequencies lower to cutoff frequencies and attenuate the higher frequencies. It mainly used in the field of acoustic, anti-aliasing filters for conditioning signals prior to analog-to-digital conversion (ADC), signal processing, images processing etc

What is a Band-pass Filter (Butterworth Filter) and how to perform it in ASI Datalab?

Band-pass Filters (BPF) can be used to filter out certain frequencies that lie within a particular band or range (lower and higher cutoff) of frequencies. This filter is combination of lowpass and highpass filter.

What is Coherence? How to calculate Coherence in ASI Datalab?

Coherence represents that the response is related to excitation/reference signal. Two signals (Response and excitation/reference) is considered as coherent if it has constant phase difference and same frequencies.

What is Cross Spectral Density (CSD)? How to calculate CSD in ASI Datalab?

Cross Spectral Density (CSD) uses two discrete time domain signals to compare each other in terms of amplitude and phase (time delay).
It uses Welch’s modified periodogram method for computation. It requires two inputs, first being the response signal and second being the excitation/reference signal. The output is a function of frequency (Hz) in complex (Real & Imaginary) form.

What are Arithmetic Operations (Signal and Signal) & How to perform them in ASI Datalab?

Arithmetic Functions (Signal & Signal) are used for Adding, Subtracting, Multiplying and Dividing a Signal value with another Signal.

What are Arithmetic Operations (Signal and Constant) & How to perform them in ASI Datalab?

Arithmetic Functions (Signal & Constant) are used for Adding, Subtracting, Multiplying and Dividing a constant value with the Signal.

What is Mean Fully Developed Deceleration (MFDD)? How to calculate MFDD in ASI Datalab?

MFDD is defined as the maximum deceleration a vehicle can achieve. Normally the deceleration between 80% and 10% of the trigger test speed.
From the test speed, the module scans the data for the last point closest to test speed.

What is Auto RMS Spectrum? How to calculate Auto RMS Spectrum in ASI Datalab?

Auto RMS spectrum is tool to convert time domain data to frequency domain, where amplitude is represented as RMS value of that frequency. It uses Fourier transform and averages of overlapped sections of the input data.

What is Power Spectral Density (PSD)? How to calculate the Power Spectral Density in ASI Datalab?

In simple word PSD represents the power of amplitude on Y axis for each frequency contents in the signal.
Ax(f)=X(f)*X(f)
Quite often PSD is called as ASD (Auto Spectral density). It is because while converting from time domain to frequency domain reference signal is same as response, whereas if reference signal is not same it is called cross spectral density.

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