Interlink Electronics FSLP Sensor - Manual (Page 13)

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11
Force Sensing Linear Potentiometer (FSLP)
Integration Guide
Step 3: Take two measurements
 Take an ADC reading on the ADC connected to sensor terminal 3. Call this V1.
 Take an ADC reading on the ADC connected to senor terminal 1. Call this V2.
Step 4: Calculate the pressure
 We know the values of V2 and R
0
. Therefore, the current through R
0
can be
calculated as
 The current I, is the same current that flows through Rp.
 No current flows through R2; therefore, the voltage drop across Rp is simply V1-V2.
 Rp now be calculated using:
 Because the value of Rp decreases with force, what we really want is the reciprocal
of the expression above:
 R
0
is a constant; therefore, we can think of it as a scaling factor. The scaling factor
should be a convenient value, typically a power of 2 (e.g. 32 or 64). Choose the value
of the scaling factor on an application-specific basis to yield the best data.
 The final expression is: