ADIS16204 Просмотр технического описания (PDF) - Analog Devices

Номер в каталоге

Компоненты Описание

производитель

ADIS16204

Programmable High-g Digital Impact Sensor and Recorder

Analog Devices 

ADIS16204

THEORY OF OPERATION

OVERVIEW

IMPACT/SHOCK RESPONSE

The ADIS16204 integrates a dual-axis ±70 g/±37 g MEMS

The sensor’s mechanical structure provides a linear meas-

acceleration sensor into a complete impact/shock measurement

urement range that is 8 times that of each axis’ actual output

and recording system. The integrated mixed signal processing

measurement range. Therefore, when considering the response

circuit digitizes the sensor data, applies corrections factors,

to high-g, short duration events, the 2-pole, 400 Hz, low-pass

provides many user-programmable features, and offers a simple

Bessel filter network influences the output response. Figure 18

communication conduit: the serial peripheral interface (SPI).

provides a frequency response for this signal chain. In Figure 19,

ACCELERATION SENSOR

the X-axis accelerometer experiences a 560 g shock event that

lasts 0.1 ms, causing the output response to reach 70 g. For users

The ADIS16204 base sensor core provides a fully differential

sensor structure and circuit path, resulting in substantial

rejection of electromagnetic interference (EMI) effects. It

uses electrical feedback with zero-force feedback for improved

accuracy and stability. The sensor’s resonant frequency is well

E beyond the cut-off frequency of the filter, which adds further

noise rejection to the sensor signal conditioning circuit.

ANCHOR

T PLATE

CAPACITORS

UNIT

E SENSING

CELL

FIXED

PLATES

MOVABLE

FRAME

L MOVING

PLATE

UNIT

FORCING

CELL

ANCHOR

O Figure 17. Simplified View of a Sensor Under Acceleration

Figure 17 is a simplified view of one of the differential sensor

S elements. Each sensor includes several differential capacitor

unit cells. Each cell is composed of fixed plates attached to the

substrate and movable plates attached to the frame. Displace-

ment of the frame changes the differential capacitance, which

B is measured by the on-chip circuitry.

Complementary 200 kHz square waves drive the fixed plates.

Electrical feedback adjusts the amplitudes of the square waves

O such that the ac signal on the moving plates is 0 V. The feedback

that need to avoid output saturation, keeping the integration of

the event’s acceleration response (acceleration-time product in

the case of Figure 19) below 56 g-ms is critical.

10

X: 418.9

0

Y: –3.291

–10

–20

–30

–40

–50

10

100

1k

10k

FREQUENCY (Hz)

Figure 18. ADIS16204 Frequency Response

600

550

560g, 0.1ms, SIMULATED SHOCK

500

450

400

350

300

250

200

150

70g, FILTERED RESPONSE

100

50

signal is linearly proportional to the applied acceleration. This

0

–0.50 –0.25 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00

unique feedback technique ensures that there is no net electro-

TIME (ms)

static force applied to the sensor. The differential feedback control

Figure 19. ADIS16204 Shock Response

signal is also applied to the input of the filter, where it is filtered

and converted to a single-ended signal.

TEMPERATURE SENSOR

This sensor reflects the sensor’s junction temperature and

provides a convenient temperature measurement for system-

level characterization and calibration feedback.

Rev. B | Page 10 of 24

Share Link: