JJF 1943-2021Calibration Specification for Shock Measuring Instruments (English PDF)

5.2 Standard devices for calibration

5.2.1 Shock acceleration standard/calibration device

The standard shock acceleration meter (or shock acceleration standard kit) or shock acceleration laser meter used as the main standard of the shock acceleration standard/calibration device shall be calibrated with the absolute shock metrology reference or metrology standard device. Other shock meters can be calibrated with the absolute or comparative shock acceleration standard device.

5.2.2 Shock waveform recorder (optional)

5.2.2.1 Digital storage oscilloscope

The oscilloscope shall have a bit number of not less than 12 bits, a sampling rate of not less than 100 MHz, a bandwidth of not less than 1 MHz, an integral error of less than

1%.

5.2.2.2 Data acquisition system

The amplitude resolution, sampling rate, storage space of the data acquisition system or waveform recorder shall meet the needs of shock acceleration measurement. Usually, the amplitude resolution of the acquisition card is not less than 10 bits; the sampling rate is at least greater than 10/T, where T is the pulse duration of the shock waveform.

For a measurement system that uses charge amplifier integration to obtain a shock velocity waveform, its single integral error shall be less than 3%; for a system that uses software integration to obtain an shock velocity waveform, its integral error shall be less than 2%.

5.2.2.3 Dynamic signal analyzer

The frequency indication error of the dynamic signal analyzer is better than 0.01%; the spectrum amplitude indication error is better than 2%; the amplitude consistency between any two channels of the instrument is better than 0.1 dB; the phase consistency is better than 1°.

5.2.3 Filter

To avoid signal aliasing and suppress noise, the filter used shall have appropriate amplitude-frequency and phase-frequency responses; the filter effect of the selected cutoff frequency shall meet the measurement uncertainty requirements.

5.2.4 Standard capacitor (optional)

The standard capacitor of 1000 pF or 10000 pF has an accuracy level of 0.1.

5.2.5 Sine signal generator (optional)

The distortion of the single-frequency sine signal generated by the sine signal generator is less than 0.1%; the frequency stability is better than 0.1%; the amplitude stability is better than 1% (8 h).

6.1 Calibration of shock acceleration peak sensitivity

Use the specified torque value to rigidly fix the accelerometer of the shock measuring instrument to be calibrated on the shock standard/calibration device; the sensitivity of the matching adaptive amplifier is set at 1 pC/Unit (or mV/Unit). It is recommended to select no less than 7 points (including the minimum and maximum acceleration peaks) within the range of the calibrated shock measuring instrument for measurement, to obtain a set of shock acceleration sensitivities Si under the conditions of a standard shock acceleration peak ai, i = 1, 2, ..., N, N is the number of shock calibration points.

The expanded uncertainty of the shock acceleration peak sensitivity Si is evaluated in accordance with Appendix A or Appendix B.

6.2 Calibration of shock acceleration peak indication error

It is recommended to select no less than 7 calibration points (including the minimum and maximum acceleration peaks) within the operating range of the shock meter; the shock meter is set to the corresponding shock acceleration sensitivity gear. Measure once at each of the selected calibration points to obtain two measurement columns {a0, i} and {a1, i} of the standard shock acceleration peak and the shock meter indication respectively. At the same time, record the corresponding pulse duration measurement columns {T0, i} and {T1, i}. The pulse duration is the time interval between the shock acceleration rising to 10% of the peak value and falling to this value. If the shock meter to be calibrated has an integration function, it is also necessary to record the velocity change {v0, i} calculated by the shock acceleration standard/calibration device and the velocity change {v1, i} calculated by the shock meter.

Calculate the acceleration indication error deltaa, i of each point according to formula (1):

6.3 Calibration of shock acceleration peak measurement repeatability

Under the condition that the standard/calibration device can produce repeated shock power; when the accelerometer is stationary, measure and calculate the variance of the noise as sigma2; the maximum measurable sinusoidal voltage peak value of this position is

U (given in the manual), then the dynamic range D (in dB) is: