A piezoelectric device includes a piezoelectric element, a package, a temperature sensitive component and a conductive adhesive. The package includes a base body and a connection conductor. The base body has electric insulation and configures a space. The space is sealed and holds the piezoelectric element. The connection conductor is located on a predetermined surface of the base body. The predetermined surface is on an outer side relative to the space. The temperature sensitive component includes apart terminal and converts temperature to an electrical signal. The conductive adhesive is configured by a thermosetting resin containing a conductive filler and is bonded to the connection conductor and the part terminal.

A piezoelectric device includes a piezoelectric element, a package, a temperature sensitive component and a conductive adhesive. The package includes a base body and a connection conductor. The base body has electric insulation and configures a space. The space is sealed and holds the piezoelectric element. The connection conductor is located on a predetermined surface of the base body. The predetermined surface is on an outer side relative to the space. The temperature sensitive component includes apart terminal and converts temperature to an electrical signal. The conductive adhesive is configured by a thermosetting resin containing a conductive filler and is bonded to the connection conductor and the part terminal.

In a crystal unit, a substrate is rectangle-shaped. A frame includes a pair of portions located in regions on the sides of a pair of short sides of the substrate on the lower surface of the substrate and forms a concave portion between these pair of portions. An electrode pad is located on the upper surface of the substrate. A connection pad is located on the lower surface of the substrate within the frame. A plurality of external terminals are located on the lower surface of the frame. A crystal element is mounted on the electrode pad. A temperature sensing element is mounted on the connection pad. A ratio S2/S1 of an area S1 of a rectangular region formed by an outer edge of the lower surface of the frame and an area S2 of a smallest rectangular region containing all of the external terminals is 0.75 to 0.91.

In a crystal unit, a substrate is rectangle-shaped. A frame includes a pair of portions located in regions on the sides of a pair of short sides of the substrate on the lower surface of the substrate and forms a concave portion between these pair of portions. An electrode pad is located on the upper surface of the substrate. A connection pad is located on the lower surface of the substrate within the frame. A plurality of external terminals are located on the lower surface of the frame. A crystal element is mounted on the electrode pad. A temperature sensing element is mounted on the connection pad. A ratio S2/S1 of an area S1 of a rectangular region formed by an outer edge of the lower surface of the frame and an area S2 of a smallest rectangular region containing all of the external terminals is 0.75 to 0.91.

An AT-cut crystal element includes a vibrator and a supporting portion. The vibrator has a planar shape with an approximately rectangular shape. The supporting portion is connected to one short side of the vibrator and has a thickness thicker than a thickness of the vibrator. The AT-cut crystal element has an oscillation frequency of approximately 76 Mhz. The vibrator has a distal end portion that is an end portion on a side opposite to the supporting portion. The distal end portion is formed to have a protrusion shape toward a distal end side thereof. The vibrator has both ends formed to have a protrusion shape toward an outside direction along the short side. The vibrator has a long side dimension L and a short side dimension W. A W/L is in a range of 0.74 to 0.79 or in a range of 0.81 to 0.93.

An AT-cut crystal element includes a vibrator and a supporting portion. The vibrator has a planar shape with an approximately rectangular shape. The supporting portion is connected to one short side of the vibrator and has a thickness thicker than a thickness of the vibrator. The AT-cut crystal element has an oscillation frequency of approximately 76 Mhz. The vibrator has a distal end portion that is an end portion on a side opposite to the supporting portion. The distal end portion is formed to have a protrusion shape toward a distal end side thereof. The vibrator has both ends formed to have a protrusion shape toward an outside direction along the short side. The vibrator has a long side dimension L and a short side dimension W. A W/L is in a range of 0.74 to 0.79 or in a range of 0.81 to 0.93.

A piezoelectric resonator for use in a sensor arrangement for detecting or measuring an analyte in a medium, comprises a quartz crystal plate, having a first crystal surface and a second crystal surface. The first crystal surface is provided with a first electrode, which has a surface area of less than 15 mm.sup.2 and the second crystal surface is provided with a second electrode. The first electrode may have a rectangular surface shape. A flow cell for use in an apparatus for detecting or measuring an analyte in a medium, comprises walls that form a sensing chamber together with the resonator, and inlet and outlet openings for leading a fluid through the sensing chamber. A part of the resonator constitutes one of the walls of the sensing chamber and is arranged such that the first electrode is situated inside the sensing chamber.

A piezoelectric resonator for use in a sensor arrangement for detecting or measuring an analyte in a medium, comprises a quartz crystal plate, having a first crystal surface and a second crystal surface. The first crystal surface is provided with a first electrode, which has a surface area of less than 15 mm.sup.2 and the second crystal surface is provided with a second electrode. The first electrode may have a rectangular surface shape. A flow cell for use in an apparatus for detecting or measuring an analyte in a medium, comprises walls that form a sensing chamber together with the resonator, and inlet and outlet openings for leading a fluid through the sensing chamber. A part of the resonator constitutes one of the walls of the sensing chamber and is arranged such that the first electrode is situated inside the sensing chamber.

Embodiments of the invention provide a quartz crystal vibrator including an AT-cut quartz crystal piece having a long side in an X axis direction and including first and second crystal planes formed on at least one side surface thereof in a Y′ axis direction, and an electrode layer formed on the AT-cut quartz crystal piece.

Embodiments of the invention provide a quartz crystal vibrator including an AT-cut quartz crystal piece having a long side in an X axis direction and including first and second crystal planes formed on at least one side surface thereof in a Y′ axis direction, and an electrode layer formed on the AT-cut quartz crystal piece.