Circuit Note

CN-0582

analog.com

Rev. A | 3 of 10

CIRCUIT DESCRIPTION

The CN0582 is a complete solution capable of measuring data from

analog sensors using the provided software or API libraries.

The system offers a variable amplitude and frequency sinusoidal

signal to drive an external shaker table as a test stimulus for

reading back different sensor responses.

The solution comes with evaluation software that provides full con-

trol over all the board’s functions. These functions include enabling

current sources and ac- or dc-coupling, input bias adjustment, data

capture in both time and frequency domain, providing a single-tone

or sweeping sinusoid, and data export.

The optional software API library is compatible with many different

environments, and was tested using LabVIEW, C#, and Python.

The API enables customers to develop their own custom functions

and complete applications.

Several key features of this solution are as follows:

►

4-channel simultaneous data acquisition

►

On-board IEPE excitation

►

IEPE input channel offsetting

►

Signal Generator:

►

Single tone or linear sweep

►

Electronic loopback testing

►

Shaker table excitation

►

CN0582 Evaluation Software

►

System configuration

►

Graphical display

►

File export (data acquisition, vibration test)

Table 1. Hardware Specifications

Specifications

Min

Typ Max

Unit/Remarks

Power Requirements

Input

Voltage

4.5

5

6

V

Current

500

600 mA

Analog Input

IEPE

Full scale

0.1m*

10

V

Bias

13

VDC

Current

source

4

mA

4 mA to 20 mA (CH3)

Resistance

249 Ω

Power

0.25 W

THD + N

-87

-84

dB, 3.3 Vp-p at

1 kHz

SNR

99

dB, 10 Vp-p at

20 Hz to 20

kHz

Accuracy

1

% error

(at greater than

100 mV)

Table 1. Hardware Specifications (Continued)

Specifications

Min

Typ Max

Unit/Remarks

Analog Output

Voltage

0.5

7

V peak-to-peak

Frequency

0.02

25

kHz

THD + N

-52

-55

dB, 7 Vp-p at

20 Hz to 20

kHz

Accuracy

1

% error

*Based on PGA setting of 1.

VIBRATION SENSOR TYPES

Piezo vs. MEMS Sensor

Traditionally, piezoelectric accelerometers have been the bench-

mark for vibration monitoring and are still the sensor of choice in

the highest sensitivity applications, or where very high accelerations

are involved. Microelectromechanical systems (MEMS) sensors

were previously deemed unusable due to their limited bandwidth,

g-range, and noise performance across frequency.

Recent advancements in MEMS sensor technology (especially with

frequency response and noise performance) make MEMS sensors

a viable alternative in many CbM applications. MEMS sensors are

typically smaller and lower cost, and have a frequency response

that extends to dc (0 Hz). One example is the CN0532, a typical

MEMS based sensor with circuitry implementing an IEPE interface.

The CN0582 is compatible with piezoelectric IEPE sensors as

well as IEPE-compatible sensors based on other technology. The

excitation current sources can be disabled, allowing connection to

voltage output sensors.

IEPE INTERFACE

Unconditioned piezoelectric sensors have a high output impedance,

making it difficult or impossible to drive any length of cable. These

sensors are also sensitive to cable movements and electromagnetic

interference, and require precision, high impedance signal condi-

tioning circuitry.

IEPE refers to a standard in which the signal conditioning electron-

ics are integrated into the sensor. The internal electronics convert

the high impedance charge output into a low impedance voltage

signal, making it easier to transmit. The standard also uses a

single conductor to provide both power and signal, which minimizes

cabling complexity.

Figure 2 shows a high level block diagram of the IEPE interface.

Power is supplied via a constant current source to the sensor.

The sensor then modulates the output voltage depending on the

measured vibration, which allows the signal to be measured across

the same line as the power source.