Project Description

SiSMoS-4: Site Survey Monitoring System

The SiSMoS-4 provides a PC-based, fast, four-channel, 24-bit data acquisition system with data-logger and spectrum analyzer for Bartington Instruments fluxgate sensors and industry standard ICP accelerometers. Applications include environmental monitoring (of EMI and vibration) for pre-installation surveys for MRI systems, electron microscopes and similar sensitive equipments. The SiSMoS-4 performs data acquisition in three channels for a triaxial sensor fluxgate or a one channel for a uniaxial accelerometers and produces both time domain and frequency domain plots showing either slow or fast trends for magnetic and vibration data in three axes.

The conversion of time-varying information into a frequency spectrum is accomplished using Fast Fourier Transforms referred to as FFT in the text. When used as a data-logger, time-stamped data can be logged (for extended periods) then retrieved and post-processed in both time and frequency domain. The system is software controlled and connection to the user’s PC is via a USB interface. Prior to data acquisition, system configuration is accomplished using the SiSMoS-4 software (Device configurationDevice configurationDevice configuration). Additional functions provided by the SiSMoS-4 system include:

  • Selectable plot of time or frequency data
  • Data post-processing (selectable filtering and averaging)
  • Availability of cursors and markers for effective measurements
  • Exports the graph data to excel file or to the clipboard in a tab-delimited format, which is accepted by most spreadsheet applications
  • Saving of plots (images) in .bmp, .eps and .emf formats for use in reports
  • Up to 10 hours operation powered by a rechargeable battery
  • 51,2 kS/s sampling rate giving a spectral plot up to 25,6 kHz (-3dB point)

The SiSMoS-4 software records time and frequency domain data over a wide frequency range – from DC to 3.5kHz  (-3dB point) for all input channels. Data logging with time-stamping is also provided hence the system functions as a high resolution data logger for magnetic and vibration measurements. The SiSMoS-4 software is compatible with Windows XP or later.

The SiSMoS-4 hardware unit contains a rechargeable battery for up to 10 hours  operation under typical conditions to allow field-work with a laptop computer. In order to extend battery operation, magnetometer power is applied only when the user must use. The system is ideal for magnetic, vibration measurements and is also suited for recording the magnetic fields due to 50/60Hz mains supplies and associated harmonics.

Specification

Number of input channels 3 for magnetic field sensors

1 for accelerometers or acoustic  sensors

Voltage input range ±10 V
Resolution 24 bit A to D converter
ADC Resolution 24 bits
Type of ADC Delta–Sigma (with analog prefiltering)
Sampling mode Simultaneous
Frequency domain display options Amplitude spectrum (RMS, peak-to-peak)

Amplitude spectral density (RMS/√Hz, p-p/√Hz)

Internal master timebase (f M)

Frequency

Accuracy

13.1072 MHz

±50 ppm max

Data rate range (f S) using internal master timebase

Minimum

Maximum

1.652 kS/s

51.2 kS/s

Input coupling AC/DC (software-selectable)
AC cutoff frequency

– 3dB

– 0.1 dB

0.5 Hz

4.6 Hz max

IEPE excitation current (software-selectable on/off)

Minimum

Typical

2.0 mA

2.1 mA

Power on glitch 90 mA for 10 ms
IEPE compliance voltage 19 V max
Overvoltage protection (with respect to chassis ground)

For a signal source connected to AI+ and AI

For a low-impedance source connected to AI+ and AI–

±30 V

-6 to 30 V

Gain drift

Typical

Maximum

0.14 mdB/°C (16 ppm/°C)

0.45 mdB/°C (52 ppm/°C)

Accuracy
Offset drift

Typical

Maximum

19.2 mV/°C

118 mV/°C

   Gain

Typical

Maximum

0.01 dB

0.04 dB

   Phase (fin in kHz) fin ? 0.045° + 0.04 max
Passband

Frequency

Flatness (fs = 51.2 kS/s)

0.45 ? fs

±40 mdB (pk-to-pk max)

Phase nonlinearity (fs = 51.2 kS/s) ±0.45° max
Stopband

Frequency

Rejection

0.55 ? fs

100 dB

Alias-free bandwidth 0.45 ? fs
Crosstalk (1 kHz) -110 dB
Spectrum range Software selected as sample rate or maximum frequency
Output interface USB2
Software Windows® 98/2000/XP/Seven compatible
Operating temperature range -10°C to +50°C (0°C to +45°C  for charging)
Storage temperature range -20°C to +70°C
Humidity 0 – 50% (non condensing)
Enclosure Aluminium
Dimensions 250 x 190 x 80 mm
Weight 3.5 kg
Connectors 1 x DB9 plug to magnetic field sensors

1 x BNC sockets for ICP® piezoelectric vibration sensors/microphone preamplifiers

1 x USB to PC

1 x IEC socket for 110-220V input from mains adaptor for recharging

Power output to sensor ±15 V, ±75mA
Sensor input (magnetic field sensor) Unbalanced
Suitable ICP® vibration sensor PCB Piezoelectronics
Battery Internal rechargeable Ni-Mh 7.2V battery with universal mains adaptor for charging
Battery life 10 hours (typical)
Battery charging time 15 hours for full charge
Power consumption from chassis

Active mode

Sleep mode

900 mW max

25 mW max

Thermal dissipation (at 70°C)

Active mode

Sleep mode

930 mW max

25 mW max

Channel-to-earth ground ±30 V max, Measurement Category I
Input impedance (magnetic field sensor inputs) 1 MΩ
ICP® constant current 4mA ±20% for cables up to 1km in length
Optional accessories Tripod and adaptor for Mag-03 sensors

Rugged carrying case

Carrying case dimensions 616 x 493 x 220 mm
Total weight with carrying case 12kg with SiSMoS–4, Mag-03 sensor, 5m cable and tripod
CE Compliance 2006/95/EC; Low-Voltage Directive (safety)

2004/108/EC; Electromagnetic Compatibility Directive (EMC)