ADIS16227 데이터 시트보기 (PDF) - Analog Devices

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ADIS16227

Digital Triaxial Vibration Sensor with FFT Analysis and Storage

Analog Devices 

Data Sheet

ADIS16227

POWER-DOWN

Set GLOB_CMD[1] = 1 (DIN = 0xBE02) to power down the

Table 14. Sample Rate Settings and Filter Performance

Sample Rate Bin Width Bandwidth Noise

Setting (SPS)

(Hz)

(Hz)

(mg)

ADIS16227. To reduce power consumption, set REC_CTRL[7]

= 1 to automatically power down after a record has completed.

Toggle the CS line from high to low to wake the device up and

SR0

100,189

196

SR1

12,524

25

SR2

1566

3.1

26,000

467

6,262

260

783

100

place it in an idle state, where it waits for the next command.

SR3

196

0.38

98

38

When configured as an external trigger option, toggling DIO1

or DIO2 can wake the device up as well. Using DIO1 or DIO2

for this purpose avoids the potential for multiple devices

contending for DOUT when waking up with the CS line

Table 15 provides the data sampling time (TS) for each sample

rate setting. This represents the time it takes to record data for

all three axes of vibration data.

approach. After completing the record cycle, the device remains

awake. Use GLOB_CMD[1] to put it back to sleep after reading

the record data.

RECORD STORAGE MODE

E After the ADIS16227 finishes processing FFT data, it stores the

data into the FFT buffer, where it is available for external access

using the SPI and x_BUF registers. REC_CTRL[3:2] provides

programmable conditions for writing buffer data into the FFT

T records, which are in nonvolatile flash memory locations. Set

REC_CTRL[3:2] = 01 to store FFT buffer data into the flash

memory records only when an alarm condition is met. Set

E REC_CTRL[3:2] = 10 to store every set of FFT data into the

flash memory locations. The flash memory record provides

space for a total of 16 records. Each record stored in flash

memory contains a header and frequency domain (FFT) data

L from all three axes (x, y, and z). When all 16 records are full,

new records do not load into the flash memory. The

REC_CNTR register (see Table 13) provides a running count

for the number of records that are stored. Set GLOB_CMD[8] =

O 1 (DIN = 0xBF01) to clear all of the records in flash memory.

Table 13. REC_CNTR Bit Descriptions

Bits Description (Default = 0x0000)

S [15:5] Not used

[4:0] Total number of records taken, range = 0 to 16, binary

SAMPLE RATE OPTIONS

B The analog-to-digital converter (ADC) samples each accelero-

meter sensor at a rate of 100.2 kSPS (fs). REC_CTRL[11:8] provide

four different sample rate options for FFT analysis: SR0 (fs),

O SR1(fs ÷ 8), SR2 (fs ÷ 64), and SR3 (fs ÷ 512). The reduced rates

Table 15. Sample Times, TS

Sample Rate Setting

SR0, REC_CTRL[8] = 1

SR1, REC_CTRL[9] = 1

SR2, REC_CTRL[10] = 1

SR3, REC_CTRL[11] = 1

Sample Time (ms), TS

5.27

42.15

337.17

2697.39

If more than one sample rate setting is active in REC_CTRL[11:8],

the sample rate setting automatically updates after each FFT

event and waits for the next trigger input. The order of priority

starts with the highest sample rate enabled and works toward the

lowest after each REC_CTRL[11:8] write cycle. When used in

conjunction with automatic trigger mode and record storage,

FFT analysis for each sample rate option requires no further

user inputs, except for collecting the data. Depending on the

number of FFT averages, the time period between each sample

rate selection may be quite large. Note that selecting multiple

sample rates reduces the number of records available for each

sample rate setting, as shown in Table 16.

Table 16. Available Records

Number of Sample Rates Selected

1

2

3

4

Available Records

16

8

5

4

WINDOWING OPTIONS

REC_CTRL[13:12] provide three options for pre-FFT

windowing of time data. For example, set REC_CTRL[13:12] =

01 to use the Hanning window, which offers the best amplitude

resolution of the peaks between frequency bins and minimal

come from a decimation filter, which reduces the bandwidth

broadening of peak amplitudes. The rectangular and flat top

and bin widths. See Figure 13 for the filter location in the signal

windows are also available because they are common windowing

processing diagram and Table 14 for the performance trade-offs

options for vibration monitoring. The flat top window provides

associated with each sample rate setting.

accurate amplitude resolution with a trade-off of broadening

the peak amplitudes.

Rev. B | Page 11 of 24

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