DA6510.009

6 September, 2018

23 (32)

CAPACITANCE MEASUREMENT MODES (continued)

INT

DIFF

REF

MIN

LIN

EXT

C

K

C

C



−



−

=



%

80

_

_

,

INT

DIFF

REF

MAX

LIN

EXT

C

K

C

C



−



=



%

80

_

_

Equations 8a, 8b.

TOT

EXT

DIFF

REF

MIN

LIN

EXT

MAX

LIN

EXT

TOT

LIN

EXT

C

K

C

C

C

C

_

_

_

_

_

_

_

8

.

0

6

.

1





=



=



−



=



Equation 8c.

Example:

capacitance difference measurement range values.

Capacitance values of offset capacitance matrices:

Overall input range:

Linear input range:

Note that above calculated values are capacitance difference values between external sensor (CS) and external

reference (CR) side capacitances (

that can be measured.

Capacitance ratio mode

RATIO

INT

S

EXT

S

INT

R

EXT

R

RATIO

S

R

K

C

C

C

C

CODEFS

K

C

C

CODEFS

CODE



















+

+

−



=















−



=

_

_

_

_

1

1

Equation 9.

where

CODEFS = M

aximum output code range which depends on OSR selection. See page 7 “Full scale output code

range” specification in the ELECTRICAL CHARACTERISTICS table.

Equation 10.

External sensor + internal sensor matrix capacitance between CS and CC pins

External reference + internal reference matrix capacitance between CR and CC pins