A Conditioner Optimized for Vibration Measurements on Submarines and Surface Ships in High EMI Environments

Precision Filters’ 8-channel 28918A conditions IEPE accelerometers, CVLD accelerometers, in-line pre-amps and voltage signals and is particularly well-suited for making underwater acoustics noise and vibration measurements, especially in high electromagnetic interference (EMI) environments.

The 28918A is a dual mode card operating in either CVLD mode or IEPE mode.

In CVLD mode, the 28918A is compatible with specialized CVLD sensors that have enhanced immunity from EMI noise sources plaguing modern day submarines and surface ships. In CVLD sensors vibration signals are presented as a proportional output current, rather than proportional voltage as in traditional IEPE type accelerometers. The 28918A converts and conditions the variable output current and provides clean, amplified, and data-acquisition-ready voltage signals for attached A/D convertor systems. Using the 28918A, small AC current signals are detected even in the presence of the high-level noise that is common with cabling in high EMI environments. The constant voltage CVLD excitation is programmable to 10 or 15 V. A buffered system test bus signal can be injected into the CVLD input circuit or connected via a third-wire connection to a CVLD equipped with a calibration input.

In IEPE mode, the 28918A is compatible with either floating or grounded sensors with programmable IEPE current up to 12 mA. The 28918A provides an overall amplifier gain up to x1024 and maximum bandwidths from 30 kHz (filtered) to 190 kHz (wideband).

The 28918A 8-Channel CVLD/IEPE Conditioner is a member of the Precision 28000 family of signal conditioners.

28000 Signal Conditioners

28918A Applications:

  • Vibration Measurements in Environments with High EMI Noise
  • Platform Noise
  • Structure-Borne Noise
  • Acoustic Receivers
  • Dynamic Vibration, Load, Torque, Pressure, and Force Measurements in Industrial Environments
  • Machine Health Monitoring
  • Structural Response Tests

28918A 8-Channel CVLD/IEPE Conditioner Features:

  • 8 channels/card
  • 128 channels per 28016 chassis
    64 channels per 28008 chassis
    32 channels per 28004 chassis
  • IEPE, CVLD or voltage inputs
  • Isolated IEPE mode to break cabling ground loops
  • Bandwidths up to 30 kHz (filtered) or 190 kHz (wideband)
  • Compatible with Constant Voltage Line Drive (CVLD) sensors
  • Programmable IEPE current to 0, 4, 8 and 12 mA
  • Programmable CVLD excitation 10 or 15 V
  • Programmable amplifier: x½ to x1024 with 0.05 x steps
  • 4-pole low-pass filters with filter bypass (wideband)
  • 0.2% measurement accuracy
  • 15nV/√Hz noise floor
  • Sensor CAL signal for CAL equipped CVLD sensors


Signal Conditioning Verification logo

Verification at Test Time

Continual setup, tear down and reconfiguring of sensitive test equipment demands a rigorous protocol to prove that every channel is operating correctly at test time. The 28000 System provides a layer of built-in verification and validation capability to confirm proper operation of the measurement system including sensor and cable. Upon completion of the verification testing, a status report is provided as a defendable means to document system validity at the time of the actual test.

Yearly Calibration

All test systems require periodic calibration. The Precision 28000’s automated built-in test capabilities allow the user to perform convenient, affordable NIST traceable yearly calibration tests on-site without removing the system from the equipment rack. This eliminates the need for expensive off-site calibrations and system downtime.

Learn more about 28000 NIST Traceable Testing >