The instrument is a high quality multi-purpose charge amplifier. It is intended for joint work with piezoaccelerometers and other piezoelectric measuring transducers.

The input charge amplifiers of the instrument allow to apply long connecting cables. The work of the input and output stages of every channel is carried out in the condition with "floating" earth, which allows to maintain high qualitative indications of the instrument under the conditions of real industrial interference. A universal block of formation carries out selection of the necessary range of transduction and filtration of signals, which promotes combined operation with different accelerometers in vibro-measuring systems.

The regulated filters of high and low frequencies envisaged in the instrument determine its operational frequency range and provide for effective suppression of noise, transducers own resonance frequencies and other interferences. These active filters of high and low frequencies with the slope of the curve of the frequency characteristic of 20 and 80 dB/dec, respectively, have got a discretely regulated cut-off frequency.

The values of the cut-off frequency of filters corresponding to the fall of the frequency characteristic by 3dB are marked around the knobs of the appropriate switches and have additional light-emitting diode indication. As the control of the parameters of measuring channels is carried out by electronic contactless keys, the glow of the LED means their operation. In case of failure of mechanic turning switches, the appropriate light-emitting diode does not produce any light. This fact allows to localize the trouble, which is especially important in unique unreproducable experiments.

Miniature input jacks are located on the front panel of the instrument. Outputs are designed on its back panel. Each instrument channel has 2 outputs, which allows to connect two registers to the instrument simultaneously with different sensitivity and it provides the minimum level of cross interferences. The sensitivity of the channels control is carried out by 2 groups using appropriate switches on the front panel. The sensitivity within each group for all of the channels is set equal. The control of the additional sensitivity multiplier and parameters of the filters of high and low frequencies is carried out for all of the channels simultaneously. The instrument operates from the a.c. power network of 220V.

Main technical and operational characteristics:

• Input - 2 to 8 transducers charge-voltage;
  - Output - two separate outputs A and B for each channel with the possibility of different sensitivity;
• Sensitivity - for the outputs of group A 0,25; 0,5; 1; 2; 4; 8; 16; 32; 64 and 128mV/nC;
  - Main relative error in setting sensitivity is not higher than 1%;
  - Additional multipliers of sensitivity for the outputs of group B - 1; 2; 4; 8;
  - Main relative error in setting an additional multiplier of sensitivity is not higher than 0,5%;
• Bandwidth (-3dB) - 0,3 Hz - 50kHz;
  - Irregularity of frequency-response in frequency band 1Hz - 20kHz, not higher than 1dB; the range of the charge measuring 0,05 - 40000 nC;
  - Coefficient of non-linear distortion at frequency of 160Hz with the amplitude of the input signal 7V, not higher than 0,02%;
  - Additional error in setting sensitivity from the change of supply voltage is not higher than 0,3%;
  - Maximum output voltage for all outputs with the loading resistance higher than 2kW, not higher than 10V;
  - High-pass filters - cut-off frequencies 0,3; 1 and 3 Hz (-3dB), the slope of the curve of frequency characteristic - 20dB/dec;
  - Low-pass filter - cut-off frequencies 0,25; 0,5; 1; 2,5; 5; 10; 20 and 50kHz (-3dB), the slope of the curve of frequency characteristic - 80dB/dec;
  - Error of introduced attenuation at the cut-off frequency of filters in respect to the level -3dB, not more than 1dB;
  - Referenced to the input set noise in the frequency band 3Hz - 20kHz with the transducer capacity 1nF and sensitivity 8-128mV/pC, not higher than 0,005 pC;
  - The same with the sensitivity 0,25 - 4 mV/pC, not more than 0,05 pC;
  - Referenced to the output separation between the channels is not worse than -80dB;
• Supply: a.c. network, voltage 200-240V, frequency 50-60Hz;
  - Power used - 30W;
  - Dimensions: height - 135mm, width - 155 or 230 mm, length - 350 mm;
  - Mass, not more than 5kg.

In 1996 the instrument MCA was metrologically attested in Gosstandart in Russia. In November 1997 the device was exhibited at the exhibition "EURIKA-97" in Brussels and was awarded a silver medal. There are 2-, 4- and 8-channel models of the instrument. Due to a set of unique properties the device is quite convenient for system integration. An example to build-up a complex for storing and processing vibroinformation on the basis of the described accelerators, equipment and software by Russian producers is given in the picture.

A Mobil diagnostic complex of collecting and processing information from piezoelectric transducers

Technical characteristics:

• The number of registration channels - 2 to 8;
• Frequency range - 0,3 Hz - 50 kHz;
• The type of transducers - piezoelectric;
• Maximum distance of the analogue module from the computer - 50 m;
• The analogue module of the device - CA-96, 3503, MUF (work in single ended and float ground mode);

The module of registration (company "L-card") - type E-330

• The maximum frequency of conversion - 400 kSPS;
• A signal processor ADSP-2105;
• The frequency of conversion for one channel with 2-channel input (CA-96) - 200 kSPS, with 4-channel input (3503) - 100 kSPS, with 8-channel input (MUF) - 50 kSPS;
• Resolution of ADC - 12 bits;
• Buffer storage (for all channels) - 128 kWords;
• Connection with the computer (cable up to 2,5 m) port LPT;
• Power supply: DC 5V.

Software "GeMis" (ISGI, Moscow)

• buffer storage - 2Gbyte;
• digital filtering, spectral analysis, statistical analysis, integration, differentiation;
• two-dimensional graphics, documenting;
• multimedia processing of signals.

The field of application collecting and processing information in bench impact and vibration tests, vibrodiagnostics (certification of products included). The degree of availability for service: the complex has been tested in the PHYSICAL TECHNICAL INSTITUTE Ural Branch Russian Academy of Sciences. Technical effect: increasing reliability and accuracy of vibro-measurements. The complex is portable.

Out address is:

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Sergey Mikhailovich Molin
GROUP OF EXPERIMENTAL EQUIPMENT BUILD,
PHYSICAL TECHNICAL INSTITUTE Ural Branch Russian Academy of Sciences
132, Kirov St., Izhevsk, 426000, Russia
Telephone: +7 (3412) 430302, +7 (3412) 217900
Fax: +7 (3412) 722529