Measurement Validation And Testing - Analog Devices ADICUP3029 User Manual

UG-1292

MEASUREMENT VALIDATION AND TESTING

Body Impedance
The 4-wire bioimpedance analysis (BIA) approach uses a high
precision excitation voltage source to excite the sensor with a
known high frequency voltage, V
measured and the impedance (Z) is calculated by the following
equation: Z = V /I.
AC
The AD5940 impedance test board is used to validate the
accuracy of the AD5940 measurements. The impedance test
board features an array of standard valued resistors and capacitors,
which are separated into banks labeled S1, S2, S3, S4, and S5.
Any of the resistor values can be used for body impedance tests.
The S1 bank on the board is highlighted in Figure 17 for
reference.
Select the desired resistor value to test by pushing the switch
downwards toward the row of numbers (1 to 12) on the S1 (or
S2, S3, S4, or S5) bank. Use a paperclip (or another thin, pointed
object) to change the switches by moving the switches back and
forth. Multiple resistors can be selected simultaneously to put the
resistors in series and increase the total equivalent resistance.
To perform a body impedance validation test using
the AD5940 evaluation board, take the following steps:
1. Plug the AD5940ARDZ
Arduino connectors.
2. Plug the ADICUP3029
on the board.
3. Plug the AD5940-BioElectric
the AD5940ARDZ board as in Figure 19.
4. Plug the AD5940 impedance test board into the microUSB
port on the AD5940-BioElectric
as in Figure 19.
. The response current (I) is
AC
Figure 18. AD5940
into the ADICUP3029 via the
into the PC via the microUSB port
evaluation daughter card into
evaluation daughter card
EVAL-AD5940 Evaluation Kit User Guide
Figure 17.
A schematic of the S1 bank is shown in Figure 18, with units in
ohms (Ω). R1 in the schematic corresponds to Switch 1 on the
S1 bank (S1_1). The full schematic of the impedance test board
can be found here. The S2, S3, S4, and S5 banks on the board
can additionally be used to simulate contact impedance on the
electrodes.
Impedance Test Board S1 Bank Schematic
5. Select the desired resistor value on the Z Test Board using
the S1 bank switches. The resistor selected for this test was
the S1_2 resistor, which has a value of 200Ω.
6. Ensure the
micro-USB port.
7. Open the SensorPal GUI and ensure the correct COM port
is selected.
8. Under the Bio-Electric Techniques section in the tool belt,
drag the Body Impedance measurement into the work
area. Delete any other existing measurements in the work
area by hovering over the measurement and pressing the
trash bin icon in the bottom right corner.
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AD5940 Impedance Test Board with S1_2 Activated
Figure 19. Body Impedance Hardware Setup
ADICUP3029 is connected to the PC via the