AD5933YRSZ Analog Devices Inc, AD5933YRSZ Datasheet - Page 34

• Manufacturer Part Number: AD5933YRSZ
• Description: IC NTWK ANALYZER 12B 1MSP 16SSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5933YRSZ

• Resolution (bits): 12 b
• Master Fclk: 16.776MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Supply Voltage Range: 2.7V To 5.5V
• Operating Temperature Range: -40°C To +125°C
• Digital Ic Case Style: SSOP
• No. Of Pins: 16
• Frequency Max: 0.1MHz
• Termination Type: SMD
• Pin Count: 16
• Screening Level: Automotive
• Package Type: SSOP
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Communication Function: Network Analyzer
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD5933EBZ - BOARD EVALUATION FOR AD5933
• Tuning Word Width (bits): -
• Lead Free Status / Rohs Status: Compliant
• Other names: AD5933BRSZ; Q2204656A

AD5933
ELECTRO-IMPEDANCE SPECTROSCOPY
The AD5933 has found use in the area of corrosion monitoring.
Corrosion of metals, such as aluminum and steel, can damage
industrial infrastructures and vehicles such as aircraft, ships,
and cars. This damage, if left unattended, may lead to premature
failure requiring expensive repairs and/or replacement. In
many cases, if the onset of corrosion can be detected, it can
be arrested or slowed, negating the requirement for repairs or
replacement. At present, visual inspection is employed to detect
corrosion; however, this is time consuming, expensive, and
cannot be employed in hard-to-access areas.
An alternative to visual inspection is automated monitoring
using corrosion sensors. Monitoring is cheaper, less time
consuming, and can be deployed where visual inspections are
impossible. Electrochemical impedance spectroscopy (EIS) has
been used to interrogate corrosion sensors, but at present large
laboratory test instruments are required. The AD5933 offers an
accurate and compact solution for this type of measurement,
enabling the development of field deployable sensor systems
that can measure corrosion rates autonomously.
Mathematically, the corrosion of aluminum is modeled using an
RC network that typically consists of a resistance, R
with a parallel resistor and capacitor, R
would typically have values as follows: R
R
a typical Bode plot, impedance modulus, and phase angle vs.
frequency, for an aluminum corrosion sensor.
P
1 is kΩ to 1 MΩ, and C
P
is 5 μF to 70 μF. Figure 44 shows
P
and C
S
is 10 Ω to 10 kΩ,
P
. A system metal
S
, in series
Rev. C | Page 34 of 44
To make accurate measurements of these values, the impedance
needs to be measured over a frequency range of 0.1 Hz to 100 kHz.
To ensure that the measurement itself does not introduce a
corrosive effect, the metal needs to be excited with minimal
voltage, typically in the ±20 mV range. A nearby processor
or control unit such as the ADuC702x would log a single
impedance sweep from 0.1 kHz to 100 kHz every 10 minutes
and download the results back to a control unit. To achieve
system accuracy from the 0.1 kHz to 1 kHz range, the system
clock needs to be scaled down from the 16.776 MHz nominal
clock frequency to 500 kHz, typically. The clock scaling can be
achieved digitally using an external direct digital synthesizer
like the AD9834 as a programmable divider, which supplies a
clock signal to MCLK and which can be controlled digitally by
the nearby microprocessor.
100k
10k
100
1k
10
0.1
Figure 44. Bode Plot for Aluminum Corrosion Sensor
1
10
FREQUENCY (Hz)
100
1k
10k
100k
–75
–50
–25
0