False Piezoresistive Effect Detection

Possibility of the use commercial carbon-polymer pastes for preparation thick-film resistors for linear strain sensors application was tested. The research showed that the polymer thick-film resistors are characterized by the piezoresistive effect up to 2% strain. For higher strain small cracks appeared in the resistive film. Presence of the cracks influenced resistance of the sensor. It is so called false piezoresistive effect. The cracks may cause instability of the sensor. Visual detection of the cracks is hardly possible because of their small dimensions. The indicator of cracks creation in resistive film was found.