[2SMPP-02] Application Note No.MDMK-13-0184 Application Note 01 Usage of Pressure Sensor 2SMPP-02 Copyright 2013 OMRON Corporation. All Rights Reserved. 1 [2SMPP-02] Application Note No.MDMK-13-0184 INDEX 1 OUTLINE ..................................................................................................................................3 2 STRUCTURE OF PRESSURE SENSOR .................................................................................3 3 DIMENSIONS ...........................................................................................................................4 4 PRINCIPAL OF PRESSURE DETECTION...............................................................................5 5 SPECIFICATIONS OF 2SMPP-02............................................................................................7 6 FEATURES OF PRODUCT ......................................................................................................7 7 USAGE .....................................................................................................................................8 7.1 7.2 7.3 7.4 CONNECTION METHOD .............................................................................................................8 EXAMPLE OF RECOMMENDED CIRCUIT ....................................................................................10 OUTPUT CHARACTERISTICS 1: BASIC OUTPUT CHARACTERISTICS OF 2SMPP-02 ELEMENTARY SUBSTANCE ..........................................................................................................................11 OUTPUT CHARACTERISTICS 2: BASIC OUTPUT CHARACTERISTICS BY USING RECOMMENDED CIRCUIT ................................................................................................................................11 8 GLOSSARY............................................................................................................................12 9 WARRANTY AND LIMITED LIABILITY .................................................................................13 10 CONTACT ..............................................................................................................................15 11 HISTORY ................................................................................................................................15 Copyright 2013 OMRON Corporation. All Rights Reserved. 2 [2SMPP-02] Application Note No.MDMK-13-0184 1 Outline This document shows an overview of plus an example of a circuit and the recommended connection method to use with the Omron Gauge type pressure sensor (2SMPP-02). 2 Structure of Pressure Sensor Fig. 1 shows the structure of 2SMPP-02. Each unit is [mm]. Air inlet hole Stem ステム Lead frame リードフレーム Sensor Chip センサーチップ Cover bonding material カバーボンド樹脂 Wire ワイヤー Cover カバー 9.85mm Fig. a TOP View Lead frame リードフレーム Sensor Chip センサーチップ 8.25mm 4.75mm PP02 1234 Cover カバー Bonding material ボンディング樹脂 Stem ステム Stem ステム Pressure 圧力 Wire ワイヤー Fig. b Inside TOP View Fig. 1 Fig. c CROSS Section The structure and parts name of 2SMPP-02 Copyright 2013 OMRON Corporation. All Rights Reserved. 3 [2SMPP-02] Application Note No.MDMK-13-0184 3 Dimensions Fig. 2 shows the outline dimension of 2SMPP-02. Each unit is [mm]. ① Air inlet hole ④ Cavity No. Height of Character 0.4mm The recommended tube inside diameter is 2 mm. Fig. 2 Outline dimension of 2SMPP-02 Copyright 2013 OMRON Corporation. All Rights Reserved. 4 [2SMPP-02] Application Note No.MDMK-13-0184 4 Principal of Pressure detection Omron’s 2SMPP series pressure sensors utilize a piezo-resistive type sensing element. Fig. 3 shows image of overview of Piezo-resistive pressure sensor chip. The diaphragm (blue circle of a Fig. a) is a thin disc, formed on a silicon wafer and deformed by pressure difference between upper and lower. Piezoresistors (green part of Fig. b & Fig. c) are arranged on four points of this thin diaphragm. Aluminum アルミ配線 wire Piezoresistance ピエゾ抵抗 Vout(+) Bonding-Pad ボンディング・パッド Vcc Nsub Piezoresistance ピエゾ抵抗 1.3mm Contact コンタクト GND Vout(-) 1.3mm Fig. a Top view Pressure 圧力 Fig. b Fig. 3 Null Pressure Fig. c Add Pressure Piezoresistive pressure sensor image and state of change diaphragm Atmospheric pressure (Light blue arrow) pushes down on the diaphragm, and the pressure to be measured (Pink arrow in Fig. c) pushes up from the bottom of the diaphragm. In Fig. b, the target pressure (green arrow) is equal to atmospheric pressure, so it is a condition that does not bend the diaphragm. In Fig. c, the target pressure (Pink arrow) is bigger than atmospheric pressure (Light blue arrow), so the diaphragm is pushed up. Under this condition, the deflection of the diaphragm changes the piezoresistance's value on the upper surface of diaphragm. Copyright 2013 OMRON Corporation. All Rights Reserved. 5 [2SMPP-02] Application Note No.MDMK-13-0184 Fig. 4 shows how to convert from piezoresistance value change to output voltage change. If the pressure applied to the upper and lower diaphragms are balanced, the bridge output voltage V0 is represented by formula 1.1. In theory V0 is zero if R1=R2=R3=R4, as the voltage is generated by a slight variation in manufacturing , and is defined as Voffset . Upon deflection of the diaphragm, pressure equilibrium is broken and each of the resistances of the piezoresistive are changed from R to R ± ⊿ R. Piezoresistive change in the resistance value which is arranged diagonally as shown by the arrows in the figure has the same tendency (increase or decrease). In case of the condition R=R1=R2=R3=R4 formula 1.1 applies, however when the piezoresistive value has changed from R to R ± ⊿ R formula 1.2 applies. This voltage is called the span voltage, by supplying a constant current I, the amount of change can be detected as a voltage V0 resistance value change amount(⊿ R). Since there are manufacturing variations in the piezoresistive R1/R2/R3/R4 as described above, the approximate expression of the span voltage is found in formula 1.3. Icc R1 R1 Bridge output voltage（Vo） R2 R2 ⎞ ⎟⎟ ⋅ I ⎠ ・・・Eq 1. 1 Span Voltage（Vo） ⎛ ( R + ⊿R ) ⋅ ( R + ⊿R ) − ( R − ⊿R ) ⋅ ( R − ⊿R ) ⎞ ⎟⎟ ⋅ I V 0 = ⎜⎜ ( ) ( ) ( ) ( ) + + − + + + − R R R R R R R R ⊿ ⊿ ⊿ ⊿ ⎝ ⎠ Vo R4 R4 ⎛ R ⋅ R − R2 ⋅ R4 V 0 = ⎜⎜ 1⋅ 3 ⎝ R1 + R 2 + R3 + R 4 R 3 R3 = ⊿R ⋅ I ・・・Eq 1.2 Span Voltage（Vo） V 0 = ⊿R ⋅ I + V offset Fig. 4 ・・・Eq 1.3 Theoretical formula and the electrical equivalent circuit of Piezo-resistive pressure sensor Copyright 2013 OMRON Corporation. All Rights Reserved. 6 [2SMPP-02] Application Note No.MDMK-13-0184 5 Specifications of 2SMPP-02 Table 1 shows the main specifications of 2SMPP-02. Table 1 Specifications of 2SMPP-02 Item Pressure Type Applicable gases Driven method Item Description Gauge Pressure （Note 1）（Note 3） Air （Note 2） Constant Current Supply Min Typ Max Unit Note Pressure Range 0 37 kPa Withstand Pressure 0 53 kPa Supply Current 100 uADC Max Supply Current 130 uADC Ambient Operating Temp 0 50 ℃ Ambient Storage Temp -30 85 ℃ Ambient Operating 15 90 %RH Humidity Ambient Storage Humidity 10 95 %RH Electrical Characteristic（Temperature：23[℃], Drive current：100[uA] Constant current） Item Min Typ Max Unit Bridge Resistance Offset Voltage（Note 3） Span Voltage（Note 3） Non-Linearity（Note 3） Hysteresis（Note 3） Temp influence of Span 18 20 22 kΩ -6.5 -2.5 1.5 mV 27.9 31.0 34.1 mV %FS（Note 3） -0.8 0.8 %FS（Note 3） -0.5 0.5 -0.5 0.5 1.5 %FS（Note 3） -0.7 0.3 1.3 %FS（Note 3） Temp influence of Offset -3.0 3.0 （Note 1）：Standard product is not calibrated for negative pressures. （Note 2）：Please use dry gases, and avoid dust or corrosive gases. （Note 3）：For the meaning of the unit, characteristics, refer to Chapter 8. 6 Note at 37[kPa] pressure 0～37[kPa] 0～37[kPa] 0[℃] 50[℃] 0～25[℃]/0～50[℃] Features of Product As discussed in the section on the principle of pressure sensing, piezoresistive type sensors to minimize the variation in piezoresistive leads to minimization of measurement error. By using CMOS technology which is applied to the production of highly integrated semiconductor, our gauge pressure sensor is able to achieve a good offset voltage, span voltage and temperature variation characteristics. Copyright 2013 OMRON Corporation. All Rights Reserved. 7 [2SMPP-02] Application Note No.MDMK-13-0184 7 Usage 7.1 Connection method As shown in Fig. 5, when a constant current of 100uA is provided to the Piezoresistor between terminals 6 and 3. the output voltage, depending on the pressure change, will be output between terminal 1 and 4. Short-circuit terminals 5 and 6 in use and solder terminal 2 to the board, but leave open connection. Refer to the 100uA constant current circuit (Chapter 8.2) before use. i＝100uA → ５ ６ Constant current source ＋ Ｒ２ ↑ Ｒ１ １ Output Voltage ４ Ｒ３ － Ｒ４ ３ ③ ② ① Pin No. 1 2 3 4 5 6 ④ ⑤ Pin Name Vout(+) No Connect GND Vout(-) N-sub Icc ⑥ Fig.5 Equivalent Circuit and Connection Diagram of 2SMPP-02 Be sure to check that there is no leak path between each terminal by solder paste before actual use. The desired characteristic may not be achieved if there is the influence of a leak path. Copyright 2013 OMRON Corporation. All Rights Reserved. 8 [2SMPP-02] Application Note No.MDMK-13-0184 Fig. 6 shows the recommended mounting pad layout of 2SMPP-02. In order to penetrate the pressure port through the mounting board, through-hole of Φ4.0 mm needs to be made on a mounting board. Through-hole of Φ4.0mm for pressure port. Fig. 6 Recommended Mounting PAD Layout of 2SMPP-02 Copyright 2013 OMRON Corporation. All Rights Reserved. 9 [2SMPP-02] Application Note No.MDMK-13-0184 7.2 Example of recommended circuit An example of a recommended circuit is shown in Fig. 7. A constant current circuit and an instrumentation amplifier are used with an example of Gain=21. Herein, a power supply voltage is 5 [V]. ○ Calculation of constant current ( R1=40[kΩ] , R2=10[kΩ] ） ⎤ ⎡ 10[kΩ] ⎢5[V ] ⋅ ( 40[kΩ] + 10[kΩ] )⎥ ⎦ => Icc = ⎣ = 100[uA] 10[kΩ] R2 ⎤ ⎡ ⎢VDD ⋅ ( R1 + R 2 )⎥ ⎣ ⎦ Icc = R3 ○ Calculation of Gain ( R4～R5 , R7～R10=10[kΩ] , R6=1[kΩ] ) ⎛ 2 ⋅ 10[kΩ] ⎞ ⎛ 10[kΩ] ⎞ ⎛ 2 ⋅ R5 ⎞ ⎛ R9 ⎞ ⎟⎟ ⋅ ⎜⎜ ⎟⎟ = 21[ratio] Gain = 1 + ⎜ ⎟⋅⎜ ⎟ => Gain = 1 + ⎜⎜ ⎝ R6 ⎠ ⎝ R 4 ⎠ ⎝ 1[kΩ] ⎠ ⎝ 10[kΩ] ⎠ Herein, R4=R8, R5=R7, R9=R10 Then, final output voltage of Vout is defined as Vout = Gain ・Vs. ( Vs is sensor output voltage ) VDD = 5VDC Constant current circuit unit Amplifier circuit unit Pressure Sensor R1 = 40kOhm I s = 100uADC + + R4 = 10kOhm R9 = 10kOhm - - R5 = 10kOhm ⑥ R2 = 10kOhm ① ④ ③ R6 = 1kOhm + Vout R7 = 10kOhm + R8 = 10kOhm R3 = 10kOhm R10 = 10kOhm Reference Input EX) Ref = 1VDC Fig. 7 Example of Recommended Circuit Diagram for 2SMPP-02 In such recommended circuit diagram, instrumentation amplifier such as Texas Instruments LMV324 with four operational amplifies can be used for gain adjustment. A metal film resistor with good temperature characteristics should be used for R3. In addition, it is necessary to adjust the Ref voltage value connected to R10 according to the gain to be used. For example, if Gain = 21 then Ref = 1.0 [V], if Gain=201 then Ref = 1.5 [V] would be needed. Copyright 2013 OMRON Corporation. All Rights Reserved. 10 [2SMPP-02] Application Note No.MDMK-13-0184 7.3 Output Characteristics 1: Basic output characteristics of 2SMPP-02 elementary substance Fig.8 shows the output characteristics at room temperature (25deg-C) when applying the pressure from -10 [kPa] to 50 [kPa] at the condition of the constant current 100 uA. Note that the guaranteed measurement range of 2SMPP-02 is 0 [kPa] to 37 [kPa] that is shown by a break line in red. Span voltage at 0 [kPa] to 37 [kPa] is typically 31 [mV]. 50 Ouput Voltage[mV] 40 30 20 10 0 -10 -20 -10 0 10 20 30 40 50 Rated Pressure[kPa] Fig. 8 Output Characteristic of 2SMPP-02 (raw output voltage between Terminal 1 and 4) 7.4 Output Characteristics 2: Basic output characteristics by using recommended circuit When using the circuit configuration at the condition of Gain =21 as described in Fig. 7, the output characteristics for low pressure range between 0 [kPa] and 7 [kPa] is shown in Fig.9. In this case, Ref voltage is connected to 1.0 [V]. This is a result of monitoring the output Vout shown in Fig. 7. 2SMPP-02 Reference Circuit Result at 100uA/Gain=21 Output Voltage[V] 1.1 1 0.9 0.8 0.7 0.0 Fig.9 1.0 2.0 3.0 4.0 Rated Pressure[kPa] 5.0 6.0 7.0 Output characteristic of 2SMPP-02 after Gain=21 times In this result, it has only 0.3% of an error, even if it compares with the ideal Span voltage. The ideal Span voltage is 123mV [=7kPa / 37kPa x 31mV x 21] and actual Span voltage is 122.6mV at the condition of 0kPa to 7kPa. This means our recommended circuit can be used for even low pressure range. Copyright 2013 OMRON Corporation. All Rights Reserved. 11 [2SMPP-02] Application Note No.MDMK-13-0184 8 Glossary z Various pressure and pressure reference name A gauge pressure is a pressure relative to the atmospheric pressure. A gauge pressure which is greater than atmospheric pressure, is called positive pressure. And a gauge pressure which is smaller than atmospheric pressure, is called negative pressure. Absolute Pressure Gauge Pressure Negative Pressure Positive Pressure Differential Pressure Perfect Vacuum Atmosphere ● Reference Pressure z Offset Voltage The output voltage at Null pressure. ( 0[kPa] ). z Span Voltage It is calculated by subtracting the output voltage at Null pressure ( 0 [kPa] ) from the output voltage at Maximum rating pressure ( 37 [kPa] ). z Non-Linearity The amount of gap from an ideal output straight line and the output voltage at any pressure within the specified range which makes the deviation maximum. An ideal output line is drawn by connecting the points of output voltage at Null pressure ( 0 [kPa] ) and at Maximum rating pressure ( 37 [kPa] ). %FS notation that is normalized on the Span voltage at the time of 25 deg-C can be used. z Hysteresis The maximum output voltage deviation at any pressure within the specified range when a pressure is repeatedly applied from Null pressure ( 0 [kPa] ) to Maximum rating pressure ( 37 [kPa] ). %FS notation that is normalized on the Span voltage at the time of 25 deg-C can be used. z %FS "Percent Full Scale". Target item and amount of change are normalized on the Span voltage at the time of 25 deg-C. The percentage notation can be used. Copyright 2013 OMRON Corporation. All Rights Reserved. 12 [2SMPP-02] Application Note No.MDMK-13-0184 9 WARRANTY AND LIMITED LIABILITY Thank you for your usage of products of Omron Corporation (“Omron”). 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All Rights Reserved. 14 [2SMPP-02] Application Note No.MDMK-13-0184 10 Contact z z OMRON Electronic Components Web http://www.omron.com/ecb/index.html Contact Us For further inquiry such as delivery, price, sample and/or specification, please contact your local agency or Omron sales representative. ¾ Global Sales Office http://www.omron.com/ecb/service/network.html ¾ Mail Contact http://www.omron.com/ecb/contact/index.html ¾ Phone Micro Devices Division Tel: (81) 77-588-9200 686-1 Ichimiyake, Yasu, Shiga, 520-2362 JAPAN Place an order, accepting this Terms and Conditions. http://www.omron.com/ecb/products/order/index.html 11 History Revision Rev 1.0 DATE Oct01,2013 Note New Released Copyright 2013 OMRON Corporation. All Rights Reserved. 15