MICS-2614

Whilst e2v technologies has taken care to ensure the accuracy of the information contained herein it accepts no responsibility for the consequences of any use thereof and also reserves the right to change the specification of goods without notice. e2v technologies accepts no liability beyond the set out in its standard conditions of sale in respect of infringement of third party patents arising from the use of tubes or other devices in accordance with information contained herein.

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e-mail: enquiries@https://www.wendangku.net/doc/654170092.html, Internet: https://www.wendangku.net/doc/654170092.html, Holding Company: e2v technologies plc

e2v technologies inc. 520 White Plains Road, Suite 450, Tarrytown, NY10591 USA Telephone: (914) 592-6050 Facsimile: (914) 592-5148 e-mail: enquiries@https://www.wendangku.net/doc/654170092.html,

This datasheet describes the use of the MiCS-2614 in ozone detection applications. The package and the mode of operation described in this document target the detection of the oxidising gas O 3 in indoor or outdoor environments. Ozone is a hazardous gas, which can cause respiratory problems at concentrations above 100 ppb.

FEATURES

? Low heater current ? Wide detection range ? High sensitivity ? Fast thermal response ? Miniature dimensions

? High resistance to shocks and vibrations

IMPORTANT PRECAUTIONS

Read the following instructions carefully before using the MiCS-2614 sensor described in this document to avoid erroneous readings and to prevent the device from permanent damage.

? The sensor must not be wave soldered without

protection, or exposed to high concentrations of organic solvents, ammonia, or silicone vapours, to avoid poisoning the sensitive layer. ? Heating powers above the maximum rating of 95 mW

can destroy the sensor due to overheating. ? After exposing the sensor to high concentrations of O 3,

make sure the sensor is given enough time to recover before taking new measurements. ? For any additional questions, email enquiries@https://www.wendangku.net/doc/654170092.html,

or telephone +44 (0)1245 493493.

OPERATING MODE

The recommended mode of operation is a constant voltage mode. A heater power of P H = 80 mW is applied. This causes the temperature of the sensing resistor (R S ) to reach about 430 °C.

Detection of the O 3 concentration is achieved by measuring the sensing resistor R S during operation.

Product shown without cap

SENSOR CONFIGURATION

The silicon gas sensor structure consists of an accurately micro machined diaphragm with an embedded heating resistor and the sensing layer on top.

The internal connections are shown below.

Pin Connection A

B C Rh1 D Rs1 E F Rh2 G Rs2 H J K

Fig. 1: MiCS-2614 configuration (bottom view).

MiCS-2614O 3 Sensor

Rs: sensor resistance Rh: heater resistance

POWER CIRCUIT EXAMPLE

As shown below, one external load resistor can be used to power the heater with a single 5 V power supply.

Figure 2: MiCS-2614 with recommended supply circuit (top view)

R is 82 Ω. This resistor is necessary to obtain the right temperature on the heater while using a single 5 V power supply. The resulting voltages is typically VH = 2.35 V.

MEASUREMENT CIRCUIT EXAMPLE

As shown below, the sensitive resistance shall be read by using a load resistor.

Figure 3: MiCS-2614 with measurement circuit (top view)

The voltage measured on the load resistor is directly linked to the resistance of the sensor. RLOAD must be 820 Ω at the lowest in order not to damage the sensitive layer.

SENSOR CHARACTERISTICS

Fig. 4: R S /R 0 as a function of gas concentration at 50% RH and 25 °C.

0.01

0.11

10

10

1001000

O 3 [ppb]

R S / R 100p p b

ELECTRICAL CHARACTERISTICS

Unit Rating Symbol

Value/Range

Maximum heater power dissipation (see

P H 95 mW

note 1)

Maximum sensitive layer power dissipation P S 1 mW

Voltage supply V supply 4.9 – 5.1 V

Relative humidity range R H 5 – 95 %RH

Ambient operating temperature T amb-40 – 70 °C

Storage temperature range (see note 2) T sto-40 – 50 °C

Storage humidity range RH sto 5 - 95 %RH

OPERATING CONDITIONS

Max

Unit

Typ

Min

Parameter Symbol

Heating power (see note 3) P H 80 66 95 mW

Heating voltage V H 2.35 - - V

Heating current I H 34 - - mA

Heating resistance at nominal power

R H 68 58 78 Ω

(see note 4)

SENSITIVITY CHARACTERISTICS

Unit

Max

Characteristic Symbol

Min

Typ

O3 detection range FS 10 1000 ppm

Sensing resistance in air R0 11 3 60 kΩ

Sensitivity factor (see note 5) S R 2 1.5 4 -

Notes:

1. Heating powers above 95 mW can cause permanent damage to the sensor due to overheating.

2. Storage of parts in original shipping package.

3. To ensure a correct operating temperature, the heater voltage should be ajusted so that the resulting heating power equals

80 mW. Lower heating power will reduce the sensitivity and increase the response time. Heating powers above 95 mW can

cause permanent damage to the sensor due to overheating.

4. Heating resistor values from sensors out of production range between 58 and 78 Ω measured at V H = 2.35V. Due to material

properties of the heating resistor its value increases during operating life.

5. Sensitivity factor S R is defined as R s at 100 ppb of O3 divided by R s at 50 ppb of O3. Test conditions are 50 ± 5% RH and 25

±2 °C.

PACKAGE OUTLINE

SOLDERING PADS GEOMETRY

e2v semiconductor gas sensors are well suited for leak detection and applications requiring limited accuracy. Their use for absolute gas concentration detection is more complicated because they typically require temperature compensation, calibration, and sometimes as well, humidity compensation. Their base resistance in clean air and their sensitivity can vary overtime depending on the environment they are in. This effect must be taken into account for any application development (1087-1.1).