Condensed Fft - Multitech REVEAL User Manual

The range for the temp sensor is 0C to 100C.
The bias voltage should sit at the midpoint of the voltage reference to the accelerometer. For example, if the
accelerometer is powered at 3.3V, the bias should be 1.65V. If the bias voltage is not at this midpoint, it could
indicate a cabling issue, a broken accelerometer, or some other problem in the system. The bias voltage byte in the
uplink message must be divided by 100 to obtain the actual value. For example, if the bias voltage byte is 0xA5 or
165 decimal, the bias voltage is 1.65V.

Condensed FFT

FFTs are important for identifying specific conditions in vibration analysis, but sending a full FFT over a LoRaWAN
network is not feasible with respect to payload sizes, power consumption, on-air time, and other considerations.
Thus, the vibration sensor sends a "Condensed FFT" which provides both total energy and peak energy from
specific frequency bands in the FFT. The following table defines the eight bands that are reported:
Band
0
1
2
3
4
5
6
7
The frequency ranges in the above table represent important bands required for diagnosing common failure
conditions. For all of the eight bands, a total energy value is reported which is the sum of all bins in the FFT
between those two frequencies, and a peak energy value which is just the peak value from a single bin between
the two frequencies.
The uplink messages for the condensed FFT are shown in the table below
Byte
0
1-2
3-4
5-6
7-8
Reveal™ Wireless Vibration Sensor User Guide
Frequencies
10-20Hz
21-40Hz
41-55Hz
56-70Hz
71-110Hz
111-130Hz
131-230Hz
231Hz+
Description
Payload definition byte
Bits 7:4 Payload type (see Condensed FFT Payload
Definitions)
Bits 3:0 Channel (0x00, 0x01, 0x02, or 0x03)
Value for frequency band 0 or 4
Value for frequency band 1 or 5
Value for frequency band 2 or 6
Value for frequency band 3 or 7
SENSOR-SPECIFIC MESSAGES
21