ZETLAB Shaker control system: basic parameters measurement results

ZETLAB Shaker control system consists of:

  • vibration machine (shaker),
  • primary transducers (acceleration sensors),
  • FFT spectrum analyzer perfoming generator and voltmeter functions,
  • Special software ZETLAB shaker control system.

Below you can see the system characteristics based on ВС 133 shaker system and FFT spectrum analyzer ZET017-U4.

Input channels number 

  • 4 or 8 synchronized input channels.

Types of vibration sesnsors connected 

  • Charge output accelerometers.
  • Accelerometers with ICP power.
  • Vibration meters with current output and instant values.
  • Sensors with standard current output 4-20 mA.
  • Velocimeters.
  • Displacement sensors.

Vibration measurements frequency range

  • From 1 Hz up to 10 kHz.

Output signal dynamic range

There are several characteristics for dynamic range measurements:

  • SNR (Signal to Noise Ratio) — ratio of signal and noise
  • SFDR (Spurious Free Dynamic Range) — dynamic range without spurious components
  • SINAD (Signal to Noise Distortion Ratio) — signal ratio / (noise+ distorions)
  • THD (Total Harmonic Distortion) — total harmonic distortion coefficient (non-linear distortion coefficient)

Динамический диапазон входного сигнала

SNR is calculated as a ratio of base signal RMS to a signal without the first five harmonic components and a constant.

SNR вычисляется как отношение среднеквадратичных значений основного сигнала и сигнала без пяти первых гармоник и постоянной составляющей

Two AC voltmeters are used for measurements – the first one measures the signal RMS, the other one – the filtered signal RMS. HF filter with a cut-off frequency over 6-th harmonic components automatically eliminates the first five harmonic components and the constant.

SFDR is calculated as a ratio of carrier frequency RMS to noise harmonic component RMS (or spurious components RMS).

SFDR вычисляется как отношение СКЗ несущей частоты к СКЗ наибольшей гармонике шума (или паразитных гармоник)

The Software LPF enables value representation in dB, which considerably simplifies the calculation process. Amplitudes ratio can be substituted by logarithmic differential. Then it is possible to deduct maximum dB value of the remaining spectrum from the basic harmonic component value in dB. As you can see from the figure, it is the 5-th harmonic component that has the maximum value.

SINAD can be calculated in two ways:

  1. As a ratio of total signal power to the total noise and distortions power
  2. As a ratio of carrier frequency to noise and distortion power after signal switch-off.

SINAD

THD is calculated as a ratio of all input channels spurious harmonics RMS to the basic harmonic component amplitude:

Динамический диапазон - шум при отключенном сигнале

THD вычисляется как отношение СКЗ суммы амплитуд всех паразитных гармоник входного сигнала к амплитуде основной гармоники

The Software “Non-linear distortion analysis” enables calculation of the harmonic distortions total ratio and representation of its value in dB

THD вычисление по спектру и по анализу нелинейных искажений

Amplitude measurement basic tolerance

In accordance with verification procedure «FFT spectrum analyzer ZET 017»

  • ±(0,005Uн + 10,0 mV) up to 7 V pre-amplification coefficient = 1
  • ±(0,005Uн + 1,0 mV) up to 0,7 V pre-amplification coefficient= 10
  • ±(0,005Uн + 0,1 mV) up to 0,07 V pre-amplification coefficient= 100

If 1 V corresponds to 120 dB, then the relative tolerance should not exceed 0,13 dB.

In accordance with the applicable Technical regulations, vibration measurements relative tolerance should not exceed 1,1 dB.

Non-linear distortion coefficient

In accordance with the applicable Technical regulations, non-linear distortions coefficient should not exceed

  • 0,1%.

Galvanic separation

  • no.

Number of output channels

  • 1.

Output chanels coupling

  • Independent channel aligned with the main one, feedback provided by random sensor.

Signals reproduction frequency range

  • 0,03 … 20000 Hz.

Signals reproduction frequency range

Динамический диапазон воспроизведения сигналов

Динамический диапазон генератора

Non-linear distortion coefficient in linear and dynamic ranges

In accordance with the applicable Technical regulations, non-linear distortion coefficient should not exceed

  • 0,1%.

Output channel galvanic separation

  • No.

Available algorythms of the controller

  • Sinusoidal vibration.
  • Broad-band random vibration.
  • Classical shock.

Additional controller algorythms

  • Narrow-band spectrum.
  • Non-linear distortions measurements.
  • Integrator for calculation of vibration speed and displacement.
  • Differentiator for calculation of vibration speed and displacement.
  • Frequency response and phase-frequency response measuremets.
  • Non-linear distortions phase dependence measurement.
  • Amplitude flatness evaluation.
  • Resonance parameters measurements, intrinsic frequencies, reactance factors.
  • Random signals distribution – diagram construction.
  • Three-component sensor oscillations vector control.

Input channels: processing methods

  • By single channel.
  • Average level by several channels.
  • Maximum level by several chanels.
  • Minimum level by several channels.
  • Matched filtering by several channels.
  • Data processing in accordance with a certain formula.

Protection by limit values

Yes.

Maintained resonance: reactance factor

резонанс и антирезонанс в линейном масштабе

Real shaker system frequency responce


вершина резонанса для вычисления добротности

Diagram peak value

Since we know that the resonance reactance factor is equal to the difference of relative frequencies with signal value equal to  1/√2 of the resonance value:

добротность резонанса

прхождение резонанса с 800 Гц

Up to 70 at the speed of 1 oct/min

Sinusoidal vibration: sweep speed 

скорость развёртки по синусу 10 окт в мин

Up to 10 oct/min

Sine sweep: signal rise and fall limit speed 

скорость нарастания и спада

10 dB/sec.

BRV probability density deviation from Gaussian distribution

отклонение плотности вероятности ШСВ от гауссова распределения

BRV probability density deviation from Gaussian distribution below 1%.

System operation: signal / noise ratio 

соотношение сигнал шум

6 dB.

Controller location, connection to PC.

  • Via USB bus – up to 2 m.
  • Galvanic separation of controller and PC.
  • Possibility of placing the controller within the testing area.
  • Controller version: IP 54 or IP 68.

50-60 Hz line interference impact on controller’s operation

  • No impact.