NY10523-1482 - Datasheet Archive

 

Combined CO and NO2 Sensor This datasheet describes the use of the MiCS-4514. This is commonly, but not exclusively, used in

 

MiCS-4514 Combined CO and NO2 Sensor This datasheet describes the use of the MiCS-4514. This is commonly, but not exclusively, used in automobile applications. The package and the mode of operation described in this document describe the detection of reducing gases such as CO and hydrocarbons, and oxidising gases such as NO2. A typical application for this type of sensor is in areas that are subject to emissions from automobile exhausts. FEATURES · Low heater current · Wide detection range · Wide temperature range · High sensitivity · Short pre-heating time · Two sensors in one SMD package with miniature dimensions · High resistance to shocks and vibrations · Compliant with automotive test requirements OPERATING MODE The recommended mode of operation is constant power on each sensor. The nominal power for the RED sensor is PH = 76 mW, while the nominal power for the OX sensor is PH = 43 mW. The resulting temperatures of the sensing layers are respectively about 340 °C and 220 °C, in air at approximately 20 °C. 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 MiCS-4514 includes two sensor chips with independent heaters and sensitive layers. One sensor chip detects oxidising gases (OX) and the other sensor detects reducing gases (RED). The internal connections are shown below. Detection of the pollution gases is achieved by measuring the sensing resistance of both sensors: · RED sensor resistance decreases in the presence of CO and hydrocarbons. · OX sensor resistance increases in the presence of NO2. Pin A B C D E F G H J K Connection Rh1 OX Rs1 OX Rh1 RED Rs1 RED NC Rh2 RED Rs2 RED Rh2 OX Rs2 OX NC Rs: sensor resistance Rh: heater resistance Figure 1: MiCS-4514 configuration (bottom view) 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. e2v technologies (uk) limited, Waterhouse Lane, Chelmsford, Essex CM1 2QU United Kingdom Telephone: +44 (0)1245 493493 Facsimile: +44 (0)1245 492492 e-mail: enquiries@e2v.com Internet: www.e2v.com Holding Company: e2v technologies plc e2v technologies inc. 4 Westchester Plaza, PO Box 1482, Elmsford, NY10523-1482 NY10523-1482 USA Telephone: (914) 592-6050 Facsimile: (914) 592-5148 e-mail: enquiries@e2vtechnologies.us © e2v technologies (uk) limited 2008 A1A-MiCS-4514 Version 2, July 2008 104168 POWER CIRCUIT EXAMPLE MEASUREMENT CIRCUIT EXAMPLE As shown below, two external load resistors can be used to power both heaters with a single 5 V power supply. As shown below, the sensitive resistance shall be read by using a load resistor. Figure 3: MiCS-4514 with measurement circuit (top view) The two voltages measured on the load resistors are directly linked to the resistances of the RED and OX sensors respectively. RLOAD must be 820 at the lowest in order not to damage the sensitive layer. Figure 2: MiCS-4514 with recommended supply circuit (top view) RDRED is 82 and RDOX is 133 . These resistors are necessary to obtain the right temperatures on the two independent heaters while using a single 5 V power supply. The resulting voltages are typically VHRED = 2.4 V and VHOX = 1.7 V. OX SENSOR CHARACTERISTICS 10000 RED SENSOR CHARACTERISTICS 1 Rs/R0 Rs/R0 1000 0.1 100 10 1 10 0.01 1 10 100 1000 CO concentration [ppm] 100 NO 2 concentration [ppb] 1000 Figure 5: RS/R0 as a function of NO2 concentration at 40% RH and 25 °C, measured on an engineering test bench Figure 4: Rs/R0 as a function of CO concentration at 40% RH and 25 °C, measured on an engineering test bench © e2v technologies (uk) limited 2008 Document subject to disclaimer on page 1 A1A-MiCS-4514 Version 2, page2 ELECTRICAL CHARACTERISTICS Rating Symbol Value/Range Unit PH 88 (RED sensor)/50 (OX sensor) mW Maximum heater power dissipation Maximum sensitive layer power dissipation PS mW 4.9 - 5.1 V RH Relative humidity range 8 Vsupply Voltage supply 5 - 95 %RH Ambient operating temperature Tamb -30 - 85 °C Storage temperature range Tsto -40 - 120 °C RHsto 5 - 95 %RH Storage humidity range OPERATING CONDITIONS (RED Sensor/OX Sensor) Parameter Symbol Typ Min Max Unit Heating power PH 76/43 71/30 81/50 mW Heating voltage VH 2.4/1.7 - - V Heating current IH 32/26 - - mA Heating resistance at nominal power RH 74/66 66/59 82/73 Typ Min Max Unit SENSITIVITY CHARACTERISTICS Characteristic (RED Sensor) Symbol CO detection range FS 1 1000 ppm Sensing resistance in air (see note 1) R0 - 100 1500 k Sensitivity CO 60 ppm (see note 2) S60 - 5 50 - Symbol Typ Min Max Unit Characteristic (OX Sensor) NO2 detection range FS 0.05 5 ppm Sensing resistance in air (see note 1) R0 - 0.8 20 k Sensitivity factor (see note 3) SR - 6 - - Notes: 1. Sensing resistance in air R0 is measured under controlled ambient conditions, i.e. synthetic air at 23 ± 5 °C and 50 ± 10% RH for RED sensor and synthetic air at 23 ± 5 °C and 5% RH for OX sensor. Sampling test. 2. Sensitivity CO 60 ppm is defined as RS in air divided by RS at 60 ppm CO. Test conditions are 23 ± 5 °C and 50 ± 10% RH. Indicative values only, sampling test. 3. Sensitivity factor is defined as RS at 0.25 ppm of NO2, divided by RS in air. Test conditions are 23 ± 5 °C and 5 %RH. Indicative values only, sampling test. IMPORTANT PRECAUTIONS Read the following instructions carefully before using the MiCS-4514 described in this document to avoid erroneous readings and to prevent the device from permanent damage. · The sensor must be reflow soldered in a neutral atmosphere, without soldering flux vapours. · The sensor must not be exposed to high concentrations of organic solvents, ammonia, silicone vapour or cigarette-smoke in order to avoid poisoning the sensitive layer. · Heater voltages above the specified maximum rating will destroy the sensor due to overheating. · This sensor is to be placed in a filtered package that protects it against water and dust projections. · e2v strongly recommends using ESD protection equipment to handle the sensor. · For any additional questions, contact e2v. © e2v technologies (uk) limited 2008 Document subject to disclaimer on page 1 A1A-MiCS-4514 Version 2, page3 PACKAGE OUTLINE DIMENSIONS The package is compatible with SMD assembly process. SOLDERING PADS GEOMETRY © e2v technologies (uk) limited 2008 Document subject to disclaimer on page 1 A1A-MiCS-4514 Version 2, page 4 PACKAGING TAPE AND REEL FOR EXPEDITION The sensors are placed in a carrier tape. The dimensions of the cavity are 5.5 x 7.5 x 2.55 mm (the tolerance is ±0.2 mm). The outside diameter of the reel is either 178 ± 1 mm (for a maximum of 700 sensors) or 330 +0.25 / -4 mm (for a maximum of 2000 sensors). 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 (278-11.0). © e2v technologies (uk) limited 2008 Document subject to disclaimer on page 1 A1A-MiCS-4514 Version 2, page 5