The SP-53A is a tin dioxidesemiconductor gas sensor whichhas a good sensitivity to highconcentration ranges of

ammonia with improvedresponse speed compared withconventional models.

Structure

Gas sensitive semiconductormaterial is formed on the aluminasubstrate on which the goldelectrodes are printed. A thick filmheater of ruthenium-oxide (orplatinum) is printed on the reverseof the substrate and placed in the

housing (Fig 1).Operating conditions

Fig 2 shows the standard operatingcircuit for this model. The change ofthe sensor resistance (RS) isobtained as the change of theoutput voltage across the fixed orvariable resistor (RL). In order to

obtain the best performance andspecified characteristics, the valuesof the heater voltage (VH) circuitvoltage (VC) and load resistance (RL)must be within the range of valuesgiven in the standard operatingconditions shown in the

Specification table on the nextpage.Sensitivity characteristics

Fig 3 shows the sensitivitycharacteristics curves of the SP-53A (typical data). Sensitivitycharacteristics of the FIS gassensors are expressed by therelationship between the sensorresistance and gas concentration.The sensor resistance decreaseswith an increase of gasconcentration based on alogarithmic function.The sensitivity characteristics ofthe SP-53A is specified by thefollowing parameters.

•Sensor resistance level: atammonia 600 ppm

• Sensor resistance changeratio: between ammonia200 ppm and 600 ppmSee the specification table on thenext page for further details. The SP-53A is a tin dioxidesemiconductor gas sensor whichhas a good sensitivity to high

concentration ranges ofammonia with improvedresponse speed compared withconventional models.

Structure

Gas sensitive semiconductormaterial is formed on the aluminasubstrate on which the gold

electrodes are printed. A thick filmheater of ruthenium-oxide (orplatinum) is printed on the reverseof the substrate and placed in thehousing (Fig 1).Operating conditions

Fig 2 shows the standard operatingircuit for this model. The change ofthe sensor resistance (RS) isobtained as the change of theoutput voltage across the fixed orvariable resistor (RL). In order toobtain the best performance andspecified characteristics, the valuesf the heater voltage (VH) circuitvoltage (VC) and load resistance (RL)must be within the range of valuesgiven in the standard operatingconditions shown in theSpecification table