Sensor Workshop at ITP :: Reports / Piezo

Initial reported by Erin Kim, 2 November, 2005

Introduction

I chose the LDTM-028K, a laminated Piezo sensor from measurement specialties. It is different from resistive sensors such as the bend sensor and the photocell sensor because they generate electricity in response to applied stresses. When the piezo film is bent from the mechanical neutral axis, a very high strain within the piezo polymer is created and generates a high voltage. This voltage is created only as the sensor is deformed. The sensor produces positive voltages when they're deformed in one direction, and negative voltages when deformed in the other.

Simple Concept Diagram

image from www.makingthings.com

Structure

DT Series Elements

The DT series sensor are the simplest and standard form piezo film sensors.The capacitance is proportional to the area and inversely proportional to the thickness of the element.

LDT Series Elements with Lead Attachment and Lamination

The 'L' in LDT stands for 'laminated' sensor. Typically, a 0.005" (125㎛)polyester layer is laminated to a 28 ㎛ or 52 ㎛ piezo film element. When used in a 'bending' mode, laminated film elements develop much higher voltage output when flexed than non-laminated (i.e., DT series) elements.

Applications

TYPICAL APPLICATIONS FOR PIEZO FILM SENSORS

Accelerometer
- Car Alarm
- Biomedical Monitoring
Vibration/Motion Film Sensor

DT series

Dynamic Strain Gages
Musical Instrument Triggers

LDT series

Antitheft Alarm

Vending

Dispensing Verification
Coin Drop Counters
Antitamper
Penetration Panels

Appliance Monitering

Microwave - Sound Pickup
Washer Imbalance
Water Flow Sensor

Ultrasound
- Shockwave Sensors
- Air-Ranging Proximity
- Robotic Tactile Sensors
Audio/Acoustic
- Microphones
- Speakers
Traffic Sensors
- Vehicle Classification
- Airport Taxiway

Here are more examples using Piezo element.

Make Your Own Acoustic Guitar Pickup__student project

If it ain't got that swing...__student project

Good Application notes from MSI site.