The VMG transducer (with Sonostics BPS-II sensor) integrates a low noise accelerometer with low and high pass filtering and pre-amplification. The transducer operates in differential mode in order to achieve superior noise reduction, delivering two channels of vibration data along a three meter cable to a converter unit which both converts the signal to single-ended mode and adapts the VMG signal appropriately for use with the BIOPAC research platforms.
VMG software is optimized for the TSD250 and BIOPAC will not support or guarantee the performance of third-party transducers.
Sensor
Operational Frequency Range: 20-200 Hz
Input range: ±2 Volts
Sensitivity: 50 V/g (MP150), 0.6 V/g (MP36R)
Noise Floor: 16 mV rms (MP150), 0.8 mV rms (MP36R)
Temperature range: -55C to +125C
Maximum Shock: 2000 g
Voltage output: ±10 V (MP150), ±0.2 V (MP36R)
Type: Sonostics VMG BPS-II; microelectromechanical (MEMS) accelerometer
Cable
Length: 3 meters
Termination: RJ-25 connector (MP150), 9-pin connector (MP36R)
User Guidance
• Sample acquisition rate must be set to 2,000 Hz for proper operation of the algorithm.
• With a gain of 50 V/g the BPS-II is extremely sensitive to acceleration. To prevent saturation of the signal input when used during movements where impacts, or other high g forces are likely to occur within the pass band of the filters, signal compression technology is incorporated into the transducer. Correspondingly, muscle effort values associated with recording levels approaching the 10 V maximum that the BIOPAC A/D convertor will allow will most likely be inaccurate. Smaller movements or noise (e.g. cavitation sounds emanating from joints will not damage the transducer, and as these transients are typically short-lived (<100 ms) they rarely interfere with data analysis.
• No skin preparation is required.
• For optimal results, place transducer directly against skin surface over the muscle body to be measured.
• Either surface of the transducer can be placed against the skin surface. The convex surface may facilitate use on a concave surface.
• Only a single transducer is required to obtain muscle effort results. • Optimal results are achieved by holding the transducer against the skin with an elastic or athletic wrap using moderate pressure. Double-sided tape is acceptable to prevent movement of the transducer on the skin, though moderate pressure significantly improves recording reliability. The pressure should be sufficient to prevent movement of the transducer. Straps with Velcro attachments are acceptable as long as the Velcro is not detached while signals are being recorded, as noise generated by the detachment could contaminate the VMG signal.
• Excessive pressure, which severely compresses the muscles to be measured, is not recommended and typically results in reduced signal amplitude.
• Avoid dropping transducer onto a hard surface as such impacts can produce accelerations greater than 2000g for more than 0.1ms will destroy the integral sensing unit.
BPS--II Specifications v1.1 ©Sonostics, Inc. 2010 | 
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