Hall Effect Sensor A3144 magnet strength?

Other Hardware General Electronics
1

Hi Guys

Can anyone give me a rule of thumb as to the strength of magnet required to change the state of a A3144 hall effect sensor?
I have a batch of 10 of these sensors and not one of them is affected in any way by a neodymium magnet that takes a pull of about 20lb plus to remove from a metal surface. They are connected as per the data sheet. As I don't have access to a gauss measuring device, its a mechanical figure I'm looking for.

2

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3

Hi Spycatcher

Yes I'm using the internal pull-up resistor.
Here's the sketch I was using to check the sensors.

const int hallPin = 12;     // the number of the hall effect sensor pin
const int ledPin =  13;     // the number of the LED pin
// variables will change:
int hallState = 0;          // variable for reading the hall sensor status

void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);      
  // initialize the hall effect sensor pin as an input:
  pinMode(hallPin, INPUT_PULLUP);     
}

void loop(){
  // read the state of the hall effect sensor:
  hallState = digitalRead(hallPin);

  if (hallState == LOW) {     
    // turn LED on:    
    digitalWrite(ledPin, HIGH);  
  } 
  else {
    // turn LED off:
    digitalWrite(ledPin, LOW); 
  }
}

STOP PRESS...
Would you $%^& believe it? Out of the batch of 10, I have just found one that works. Double checked all the rest and yup, 9 faulty sensors and just one working one! Could they have been damaged by storing them in a small box in close proximity to the magnet for about a year do you think?