The Value of Analog Sensors - Film Level Case Study

When automating a process, it is easy to default to discrete sensors.  While discreet sensors are simpler and less expensive, analog sensors can provide a wide range of benefits.

Case Study – Consumable Film Roll

Many stretchwrap and shrinkwrap machines have a ‘Low Film’ detection photoeye to alert an operator before the film runs out.  These photoeyes are typically mounted parallel to the film roll in a position where the sensor changes state (ON/OFF) when the film roll decreases to a certain level.  These sensors are critical to prevent the film roll from completely running out.

This is an excellent application for an analog sensor.  With a distance sensor positioned perpendicular to the roll to monitor the diameter, not only can you alert operators when the roll is about to run out, but you can monitor the level throughout the life of the roll.

The analog sensor has many advantages:

  • Operators can monitor the level remotely.
  • Shift handoffs can be more informative to incoming operators - "The film level on machine A is down to 35%, you will need to change in first 2 hours of your shift."
  • Low level and shutdown set points can be changed without having to remount sensors.
  • Set points can be variable and recipe controlled if needed.
  • Usage rates can be calculated and run out times predicted.
  • Sensor failure can be detected prior to critical use point.

While the discreet sensor may satisfy the requirements of the machine, the analog sensor is a better tool giving operators improved control of their machine.