The Radiant Sensor Die is designed to be used as an experimental device for Individuals to build pressure or temperature sensors in experimental circuits. The die is large enough (10mm x 5mm) to be easily handled and soldered to PC boards. The die has a large 1µ-thick 4/20/80 PNZT film capacitor (4mmx4mm) to which the user can make physical contact in a variety of ways. Using charge sensing circuitry, the capacitor of the Sensor Die can see the temperature changes associated with turbulence in the air around it. For force measurements, the PNZT has a d33 of approximately 200 picocoulombs per newton. However, torque amplifies the effect of a force, increasing the effective piezo constant to almost 1000 pC/N. Because the capacitor is so thin and has a high capacitance, it must be used in charge measurement circuits, not voltage measurement circuits.
The Sensor Die is used in the Sensor Board accessory (see below) for the Radiant EDU educational tester. The PDF file for Sensor Die Detailed User Information explains how to use the Sensor Board with the EDU but also provides circuits and sensitivity information for the Sensor Die itself. It is an excellent starting point for designing your own circuits for experimenting with the Sensor Die.
The customer may recieve bare dice or dice mounted on the Sensor Die PCB, also shown on this page. Mounted dice will be poled on shipment. Bare dice will be unpoled by Radiant before being shipped to the customer. A single 15V hysteresis loop is all that is needed to pole the capacitor after soldering it to a PCB. See the datasheet below.
When soldering bare dice, the user must prevent hydrogen from reaching the capacitor. Hydrogen is the only contaminant that affects PZT. It acts in PZT much like sodium acts in silicon ICs. Hydrogen does not damage the PZT but interferes with its ferroelectric properties. Once in the capacitor, the hydrogen cannot be removed without raising the temperature of the die to 450°C in air or nitrogen, something that cannot be done while it is mounted on an printed circuit board. Hydrogen is evolved by rosin solder when the rosin disassociates from the heat of the soldering iron. To mount a Sensor Die on a PCB, do not heat the die and apply solder. Instead, pre-tin the contacts of the PCB with the solder and heat the solder until all of the rosin has been cleared from the solder. Then place the Sensor Die face down on the pre-tinned PCB pads and heat the back of the die with the iron until the solder melts and melds the die to the PCB.
Sensor Die may also be glued to a PCB face up and wires soldered to the bond bads. In this case, build a droplet of solder on the soldering iron tip and let the rosin bake out. Then touch the droplet the bond pad until adhesion occurs. To attach the wire, heat the droplet after it adheres to the bond pad.
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