My first thought here is to just use a strain gauge and monitor its output .When I worked in plastic injection factory , they used strain gages for positioning where the injection barrel was and reading out to a numeric display. So you could probably just supply the strain gage with a 5 volt signal from your Arduino , read its value to the Analog out and display it on your serial monitor,think of reading a potentiometer and outputting its value.This is a cut and paste here from a lesson from toptechboy.com, hope I don't violate any rules here.
int LEDPin=9; //assigning LED Pin
int potPin= A0; //Declaring our readValue variable
float Voltage; //Declare Voltage value
int readValue; ///Use this variable to read pot
int writeValue; //variable for writing to LED
int potPinA0On;
int potPinOff;
void setup() {
Serial.begin(9600); //turn on Serial port
pinMode(potPin,INPUT); // set potPin to Input
pinMode(LEDPin, OUTPUT);
}
void loop() {
analogWrite=(potPinA0On,51);
//readValue = analogRead(potPin); //Reads voltage
//writeValue = (255./1023.) * readValue ;//caculate real world value
//analogWrite(LEDPin, writeValue);
//Serial.print("You are writing the value of ");
//Serial.println(writeValue);
//delay(250);