Welcome to Entech Electronics Inc

Touch Screens

Operational Principles

Our resistive touchscreens are constructed from two layers of electrically conductive, transparent polyester film separated by an array of small dielectric insulators.

The polyester film is sputter coated with ITO (Indium Tin Oxide) to give it a conductive but transparent finish.

Each sheet is screen printed with a set of bus bars, one set in the X direction, the other set in the Y direction.

A controller chip periodically applies a voltage across the resistive coating of each sheet in turn. When the screen is touched, the two layers of polyester are brought into contact.

The controller senses the resulting voltage and converts it into X and Y coordinates of the touch location. This information is then transmitted to the host computer via the selected interface (eg PS2, USB, RS-232).

Electrical Specifications

Electrical specifications are typically as follows, however some performance parameters can be customised to suit individual requirements:

  • Input voltage : 4-6 VDC
  • Sheet resistivity : 300 ohms/square
  • Circuit impedance (X direction): 400ohms
  • Circuit impedance (Y direction): 225ohms
  • Maximum current : 25mA
  • Non-linearity : 1% typical (2% maximum)
  • Standard Interface : 0.1" pitch female connector

Mechanical Specifications

Touchscreen mechanical specifications are typically as follows, however some parameters can be customised to suit individual requirements:

  • Fascia material : hardcoat polyester (matt or gloss)
  • Backing plate : polycarbonate or glass
  • Light transmission : up to 85% (surface finish dependent)
  • Standard sizes : for 6", 10", 12" and 15" screens
  • Thickness : typically 2.1mm
  • Up to 35,000,000 actuations (5 wire versions)
  • Surface hardness : 3H (pencil test JIS K5400)
  • Operational : 0 to 60 deg C (95% RH)
  • Storage : -20 to 75 deg C (95% RH)
  • Actuation force : 10-30 grams