Analog Devices ADuCM355 Hardware Reference Manual page 162

UG-1262
where:
V(s) is the signal voltage.
I(s) is the calibration current.
CAL
Z (magnitude) is the magnitude of the impedance of the calibration.
CAL
Therefore,
 
V s ( ) I s ( ) Z
CAL
In Step 2,
V s ( )

I s ( )

RE RLOAD
Z

RE RLOAD 02
where:
Z is the impedance of the sensor and Load Resistor 2.
RE + RLOAD02
I(s) is the current flowing through the sensor and Load Resistor 2.
RE + RLOAD02
Therefore,
V s ( )

Z

RE RLOAD 02
I s ( )

RE RLOAD
In Step 3,
V s ( )

I s ( )
RLOAD 02
Z
RLOAD 02
where:
Z is the impedance of Load Resistor 2.
RLOAD02
I(s) is the current flowing through Load Resistor 2.
RLOAD02
Therefore,
V s ( )

Z
RLOAD 02
I s ( )
RLOAD 02
Therefore, based on Step 2 through Step 4,
 
Z Z Z

RE RE RLOAD 02 RLOAD

  

I s ( ) Z
CAL CAL

I s
  
I s ( ) Z
CAL CAL
I s
If Z (magnitude) = 200 Ω and Z
CAL

Z ( magnitude ) Z

RE RE RLOAD
where:
Z (magnitude) is the magnitude of the impedance of the sensor.
RE
I(s) values can be replaced by DFT results.

Z ( phase ) Ang
RE ( Z

RE RLOAD
 
0 Ang
I s ( )
where:
Z (phase) is the phase part of the impedance measurement of the sensor.
RE
Ang() is the function to calculate phase.
02
02
V s ( ) V s
 
02
I s ( ) I s ( )

RE RLOAD 02

1 1



I s ( ) I s ( )

RE RLOAD 02 RLOAD 02

( ) I s ( )

RLOAD 02 RE RLOAD 02

( ) I s ( )

RE RLOAD 02 RLOAD 02
(phase) = 0, it is possible to obtain the following equations:
CAL
  
Z 200 I s
02 RLOAD 02

Z )
02 RLOAD 02
 
Ang

I s ( ) I s ( )

CAL RLOAD 02 RE RLOAD 02
ADuCM355
( )
RLOAD 02

I s ( ) I s ( )
 RLOAD 02 RE RLOAD
( )

CAL
I s ( ) I s ( )

RE RLOAD 02

Ang Ang
I s ( ) I s ( )

RE RLOAD 02 RLOAD 02
Rev. B | Page 162 of 312
Hardware Reference Manual

02
RLOAD 02
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