ALTA Advanced Vibration Meter Configuration and Installation Guide

Overview

The ALTA® Wireless Advanced Vibration Meter (AVM) includes an accelerometer within a sealed cube at the end of its lead that attaches to a surface. By the end of each user-defined report interval, or Heartbeat, the Advanced Vibration Meter collects at least one measurement of 256 samples to generate a report. The report details the vibrations detected by the accelerometer through data about each of the three orthogonal axes:

1. Vibrations—peak acceleration, root mean square (RMS) acceleration, RMS velocity, or peak-to-peak displacement
2. The predominate frequency of those vibrations in Hz or RPMs
3. The crest factor—the ratio of peak acceleration over the RMS acceleration—indicates whether non-fundamental vibrations could damage a machine with a mechanically coupled surface. Or whether the surface experiences greater accelerations than the sensor is configured to measure.

The Advanced Vibration Meter also reports the duty cycle—the percentage of time between reports when vibration is present—and the temperature of the electronics within the cube.

Features

• Three-axis measurement

• Configurable Vibration Measurement modes to report Peak Acceleration, RMS acceleration, RMS Velocity, or Peak-to-Peak Displacement

• Configurable Frequency Range

• Configurable Hanning filter

• Measure vibration frequencies up to 4200 Hz / 252,000 RPM

• Configurable Measurement Interval as low as one second

• Configurable critical Vibration Aware Threshold

• Runtime indication via Duty Cycle

• Three configurable Data Report modes (Most Recent, Average, Max)

Settings to Configure

● Vibration Mode—Option to select what information the meter will generate: Velocity RMS, Acceleration RMS, Acceleration Peak, or Displacement Peak-to-Peak.

● Vibration Aware Threshold—The measured value above which the device will immediately report and enter its Aware State.

● Vibration Hysteresis—A buffer to prevent the sensor from bouncing between Standard and Aware States when the vibrations are very close to a threshold.

● Vibration Sensitivity Threshold—Measured values below this limit are ignored and will not count toward the Duty Cycle. Setting this to 0 will force the sensor to analyze every measurement (including noise) fully, and the Duty Cycle will always be 100 percent.

● Window Function—Determines which filter to apply to the FFT results. Rectangular means no filtering. Hanning minimizes spectral leakage.

● Accelerometer Range—Determines the accelerometer’s maximum observable g-force. If the actual measured values are above this setting, the peaks of the vibration waveform may be clipped, distorting the data and typically resulting in a Crest Factor below 1.41.

● Measurement Interval—In minutes between vibration measurements, each vibration measurement consists of 256 digital samples collected at the configured Sample Rate.

● Sample Rate—Determines the digital sampling frequency of the accelerometer.

● Frequency Range Minimum—Vibrations below this limit are filtered/ignored and may be set as low as Sample Rate * 2 / 256.

● Frequency Range Maximum—Vibrations above this limit are filtered/ignored and may be set as high as Sample Rate / 2.

● Power Mode—Control the power consumption of the accelerometer during measurements by changing the amount of oversampling performed. Low Power averages one reading per sample. Medium Power averages 16 readings per sample. High Performance averages up to 128 readings per sample and consumes the most power.

● Data Mode—Determines what data to display on each Heartbeat. Most Recent (Recently captured data), Average (Average of data captured over the Heartbeat), and Maximum (Maximum data captured over the Heartbeat).

Additional Feature or Option

● Scale—Permits viewing the meter’s frequency data in Hertz or RPM.

Installation Recommendations

The meter base (housing the radio and microcontroller) features mounting flanges and can be attached to most surfaces using the two included mounting screws or double-sided tape.

• For a wooden, a metallic surface, or a dry-wall surface, you can use the double-sided tape (use two pieces) or the screws.
• For masonry, use the included double-sided tape. If the screws aren’t available, use two #7, 7/16” (0.4375”) screws.
• If the included double-sided tape isn’t available, use one or more pre-cut, double-sided foam squares of dimensions 1/32” x 3/4” x 3/4” from ULINE as model number S-11695 or similar.

Mount the Accelerometer Cube

The leaded cube can be adhered to surfaces using a threaded stud, adhesives, double-sided tape, magnetic base, or a combination of all three. It is critically important that the cube is rigidly mounted to the system you wish to assess to ensure the sensor can accurately read the vibrations in the system.

Loose or non-rigid mounting can result in signal loss, unpredictable resonant frequencies, and less accurate results. The cube includes an axis indicator label to aid installation and improve the physical understanding of data reported to iMonnit.

Mounting Approaches: a through d below indicate typical mounting approaches and the generalized best-case frequency response associated with that mounting style.*

Things to Avoid: The graphic below indicates some things to avoid when mounting the cube.