A gas sensor (200) including a sensor element (10) having electrode pads (11a-12b); a separator (166); and a plurality of metal terminals (21a, 21b, 22a, 22b) each having a body portion (21a1) and a front end portion (21a2), and being insulated from each other by the separator. The separator has an element storage portion (168) penetrating in the axial-line direction or recessed toward a rear side from a front facing surface of the separator, the element storage portion has a first storage space (168a) at a front side thereof and a second storage space (168b) at a rear side thereof, the second storage space has a rotation restriction wall (168w) configured such that a relative rotation allowable angle 2θ between the sensor element and the separator is smaller than in the first storage space, and the rear end side of the sensor element is stored in the second storage space.

A sensor element for detecting a target gas to be measured in a measurement-object gas includes: an element body including an oxygen-ion-conductive solid electrolyte layer; and a protective layer covering at least a part of a surface of the element body. The protective layer includes a porous material that has a pore inside; and, in the pore in the protective layer, a ratio (Lt/Lf) of a pore length (Lt) in a thickness direction perpendicular to the surface of the element body to a pore length (Lf) in a surface direction perpendicular to the thickness direction is 0.6 to 0.9.

A sensor element for detecting a target gas to be measured in a measurement-object gas includes: an element body including an oxygen-ion-conductive solid electrolyte layer; and a protective layer covering at least a part of a surface of the element body. The protective layer includes a porous material that has a pore inside; and, in the pore in the protective layer, a ratio (Lt/Lf) of a pore length (Lt) in a thickness direction perpendicular to the surface of the element body to a pore length (Lf) in a surface direction perpendicular to the thickness direction is 0.6 to 0.9.

An evaluation and control unit (100) for a broadband lambda probe (200) and a method for operating the same are disclosed. The evaluation and control unit (100) comprises pins (RE, IPE, APE, MES) connectable to electrical wires (201, 202, 203, 204) of electrochemical cells (210, 211) of the broadband lambda probe (200), a controller (103), a ASIC reference potential source (102), wherein the ASIC reference potential source (102) is operable by means of the controller (103), a switch assembly (104) connected to each of the pins (RE, I PE, APE, MES), wherein the switch assembly (104) comprises a first transistor (T.sub.Wire) and a second transistor (T.sub.ECU), wherein the switch reference potential source (105) is connected to a gate side of the first and second transistors (T.sub.Wire, T.sub.ECU), wherein the controller (103) is configured to vary the switch reference potential (V.sub.SW) applied to the gate side of the first and second transistors (T.sub.Wire, T.sub.ECU), wherein the switch assembly (104) is configured to allow a limiting current flowing to the drain side of the first transistor (T.sub.Wire) from the ASIC reference potential if the potential at the gate side of the first and second transistors (T.sub.Wire, T.sub.ECU) is at a predetermined voltage between values of an open and closed switch.

An evaluation and control unit (100) for a broadband lambda probe (200) and a method for operating the same are disclosed. The evaluation and control unit (100) comprises pins (RE, IPE, APE, MES) connectable to electrical wires (201, 202, 203, 204) of electrochemical cells (210, 211) of the broadband lambda probe (200), a controller (103), a ASIC reference potential source (102), wherein the ASIC reference potential source (102) is operable by means of the controller (103), a switch assembly (104) connected to each of the pins (RE, I PE, APE, MES), wherein the switch assembly (104) comprises a first transistor (T.sub.Wire) and a second transistor (T.sub.ECU), wherein the switch reference potential source (105) is connected to a gate side of the first and second transistors (T.sub.Wire, T.sub.ECU), wherein the controller (103) is configured to vary the switch reference potential (V.sub.SW) applied to the gate side of the first and second transistors (T.sub.Wire, T.sub.ECU), wherein the switch assembly (104) is configured to allow a limiting current flowing to the drain side of the first transistor (T.sub.Wire) from the ASIC reference potential if the potential at the gate side of the first and second transistors (T.sub.Wire, T.sub.ECU) is at a predetermined voltage between values of an open and closed switch.

The first electrochemical oxygen sensor includes: a positive/negative electrode; and an electrolyte solution, the electrochemical oxygen sensor further including: a separation membrane for limiting an amount of oxygen supplied to the positive electrode, and a resistance element for connecting the positive electrode and the negative electrode. In one embodiment, a value of current flowing through the resistance element is 7 μA or more in an atmosphere of 50% relative humidity at 25° C. and 1 atm, and a resistance value of the resistance element is set at 1050 Ω or less. In another embodiment, a value of current flowing through the resistance element is 4 μA or more in an atmosphere of 50% relative humidity at 25° C. and 1 atm, and a resistance value of the resistance element is set so that the output voltage between both ends of the resistance element falls within a range from 4 to 9.5 mV.

The first electrochemical oxygen sensor includes: a positive/negative electrode; and an electrolyte solution, the electrochemical oxygen sensor further including: a separation membrane for limiting an amount of oxygen supplied to the positive electrode, and a resistance element for connecting the positive electrode and the negative electrode. In one embodiment, a value of current flowing through the resistance element is 7 μA or more in an atmosphere of 50% relative humidity at 25° C. and 1 atm, and a resistance value of the resistance element is set at 1050 Ω or less. In another embodiment, a value of current flowing through the resistance element is 4 μA or more in an atmosphere of 50% relative humidity at 25° C. and 1 atm, and a resistance value of the resistance element is set so that the output voltage between both ends of the resistance element falls within a range from 4 to 9.5 mV.

In a gas sensor, which measures a measurement pump current Ip3 of a measurement chamber, while switching a preliminary pump cell of a preliminary chamber ON or OFF at a constant period, there are formed in communication with each other sequentially from a gas introduction port in the interior of a structural body made from a solid electrolyte, a preliminary chamber, an oxygen concentration adjustment chamber, and a measurement chamber. The gas sensor rapidly determines a steady-state value of a measurement pump current Ip3, based on a peak value of a rate of change over time dIp3/dt of the measurement pump current Ip3, thereby hastening an ON/OFF switching period of the preliminary pump cell.

In a gas sensor, which measures a measurement pump current Ip3 of a measurement chamber, while switching a preliminary pump cell of a preliminary chamber ON or OFF at a constant period, there are formed in communication with each other sequentially from a gas introduction port in the interior of a structural body made from a solid electrolyte, a preliminary chamber, an oxygen concentration adjustment chamber, and a measurement chamber. The gas sensor rapidly determines a steady-state value of a measurement pump current Ip3, based on a peak value of a rate of change over time dIp3/dt of the measurement pump current Ip3, thereby hastening an ON/OFF switching period of the preliminary pump cell.

A gas sensor includes a sensor element, an elastic insulating member, a plurality of lead wires, a plurality of metal terminals, and a ceramic housing. The plurality of lead wires are inserted in the elastic insulating member. The plurality of metal terminals each have a first end electrically connected to the sensor element, and a second end electrically connected to a corresponding one of the plurality of lead wires. The ceramic housing includes a plurality of insertion portions each including a through hole in which a corresponding one of the plurality of metal terminals is inserted, and at least one of the plurality of insertion portions has a different height from other insertion portions.