533305 A7 _____________B7___ 五、發明説明（1 ) 埜明背景 本發明係有關於一電化學式氣體感測器，尤其是有關於 一小型、二電極式之可以用於量測各種氧化性或還原性毒 性氣體濃度的電化學式氣體感測器。 目前之毒性氣體量測大都採用電化學型式之感測方式， 而此類感測裝置通常包含有一感測電極、一參考電極和一 輔助電極，彼此相隔開，且皆與電解液相接觸。又，其中 之感測電極可以孔隙性、氣體擴散型電極製成，並使用觸 媒披覆在一與電解液相接觸的電極表面；藉此，當一目標 氧體透過擴散限制方式而進入感測電極後，將與電極表面 之觸媒以及電解液相作用，而在介面處產生一氧化或還原 反應’在此同時，輔助電極也會同時產生一還原或氧化反 應；結果’在感測與輔助電極之間將產生一感測電流，且 此電流之大小與目標氣體之濃度成線性關係。 部 中 头 n 消 1V 今 ϋ 印 tl 目前所揭之電化學型式氣體感測器大都採用不導電的鐵 ★氟龍來作爲電極之基材，進而必須從電極之靠近電解液側 的觸媒端來導接感應電流，如此亦相對地增加了電解液由 導接線洩漏的機會，甚至造成短路情形。另一方面，目前 所使用之電化學型式氣體感測器裝置基於不使電解液不致 於因爲糾述原因等造成迅速流失之考量，大都在電解液槽 與電極之間作了多重防護措施，相對地，亦使得其機構複 雜化。這類習用氣體感測器如揭露於美國專利第4 6 3 3 7 〇 4 號者。 因此’現有三電極式電化學型式氣體感測器之缺點可歸 本紙張尺度適m國家標準（CNS)以規格（21GX297公缝） (請先閱讀背面之注意事項再填寫本頁) 4 533305 A7 _____________ ___ 五、發明説明（2 ) ~' 納三點如下。 L因使用複雜機構，因而組裝較困難且費時，進而增加 製作成本，且不易於自動化生產； 2·因鐵氟龍不導電’必須由電極靠電解液之前端接冬 線，因而增加短路機會； 〇 .爲維持電解液與電極充分接觸及長期使用，常使用較 大的電解液槽。 本發明即意欲於提供一可以改進上述各項缺失的電化學 型式氣體感測器；因此，本發明之目的乃在於提供一種新 穎的電化學型式氣體感測器，其除了可以滿足使用功能之 外，並因爲結構之簡化，而能使感測器快速完成組裝，並 易於自動化生產。 經浐部中^ij.^-^h工消矜合竹it印t 爲達成上述目的，本發明之主要特徵乃在於使觸媒燒結 在一具良好導電性之多孔性碳紙上來作成各型電極，以利 採用以背向電解液之電極面來接線之方式，而避免掉導線 與電解液接觸的危險，進而得以簡化感測器之結構以及组 裝。要言之，只要將依前述方式作成之電極、導電環片、 防止電解液蒸發之鐵氟龍膜疊放在電化學槽開口處，再以 端帽密合而將前述組件緊密固定下來即可；至於輔助電極 側亦採用相同方式作成。 藉由上述万式，不僅所使用之組件相當少，且組裝極爲 容易且方便，更有利自動化生產。 此外，爲達成上述目的，並以一根表面經氣化爲氣化銀 之銀線作爲參考電極。另外，並在電化學槽内使用吸水玻 ____ - 5 - 本紙張^^^__^^叫八4規格（21()/297公釐） 533305 好浐部中次«.^-^h_T消贽合作*.印f Α7 Β7 五、發明説明（3 ) 璃纖維及膜片’以使各電極表面得以充分且均勻地接觸到 電解液。 藉此，電化學槽内之電解液容量不需要太多，即足以供 應長期使用。 ，本發明之這些及其它目的'特微、以及優點將由以下更 詳細之附帶圖式的較佳實施例説明而更爲明顯。 _圖式之簡單説明 圖1爲一根據本發明之較佳實施例而成之電化學型式氣 體感測器之分解構造剖面圖。 圖2顯示圖1所示氣體感測器檢測一氧化碳下之測試結 果。 θ 圖式之符號説明 1 感測端帽頭 2，1 5 進氣口 3，13 鐵氟龍膜 4，12 導電環片 5 感測電極 6,10 環墊片 7 電化學槽本體 8 參考電極開 9 電解液注入口 10 干擾氣體瓶 11 輔助電極 14 輔助端帽頭 16 17 電解液及吸水性玻璃纖維 參考電極 螢_明之詳細 以下’爲進一步詳細説明本發明之技術思想，特舉—較 佳實施例作一説明，惟吾人應了解其應僅用以例舉本發明 I較佳構成，而非用以限制本發明。 本纸張尺度適用中關) A鐵格（2ΐ〇χ297公楚） ' ---- ：-I ^ 搛! (請先閱讀背面之注意事項再填寫本頁) 訂 533305 A7 B7533305 A7 _____________B7___ 5. Description of the invention (1) Nominal background The present invention relates to an electrochemical gas sensor, especially a small, two-electrode type that can be used to measure various oxidizing or reducing toxic gases. Concentration electrochemical gas sensor. Most of the current toxic gas measurement uses an electrochemical type sensing method, and such sensing devices usually include a sensing electrode, a reference electrode and an auxiliary electrode, which are separated from each other and are in contact with the electrolyte. In addition, the sensing electrode can be made of a porosity, gas diffusion electrode, and a catalyst is used to cover an electrode surface that is in contact with the electrolyte; thereby, when a target oxygen gas enters the After measuring the electrode, it will interact with the catalyst and electrolyte on the electrode surface, and an oxidation or reduction reaction will occur at the interface. At the same time, the auxiliary electrode will also generate a reduction or oxidation reaction at the same time; A sensing current is generated between the auxiliary electrodes, and the magnitude of this current is linearly related to the concentration of the target gas. The head of the ministry n eliminates 1V today. Ink tl. Most of the currently disclosed electrochemical gas sensors use non-conducting iron. Fluoron is used as the substrate of the electrode, and it must be from the electrode near the catalyst end of the electrolyte side. To conduct the induced current, this will relatively increase the chance of electrolyte leakage from the lead wire, and even cause a short circuit. On the other hand, the electrochemical gas sensor devices currently used are based on the consideration that the electrolyte will not be lost quickly due to misleading reasons, etc. Most of them have multiple protective measures between the electrolyte tank and the electrode. Land also complicates its organization. Such conventional gas sensors are disclosed in U.S. Patent No. 4,363,704. Therefore, the shortcomings of the existing three-electrode electrochemical gas sensors can be attributed to the national standard (CNS) of paper size (21GX297 cm) (please read the precautions on the back before filling this page) 4 533305 A7 _____________ ___ V. Description of the Invention (2) ~ 'Three points are as follows. Because L uses a complex mechanism, it is difficult and time-consuming to assemble, which increases production costs, and is not easy to automate production; 2. Because Teflon is not conductive, the winter wire must be terminated by the electrode before the electrolyte, thus increasing the chance of short circuit; 〇. In order to maintain sufficient contact between the electrolyte and the electrode and long-term use, a large electrolyte tank is often used. The present invention is intended to provide an electrochemical type gas sensor that can improve the above-mentioned defects; therefore, the object of the present invention is to provide a novel electrochemical type gas sensor, which can meet the use function in addition to And because of the simplified structure, the sensor can be quickly assembled and easily automated. In order to achieve the above purpose, the main feature of the present invention is to sinter the catalyst on porous carbon paper with good conductivity to make various types. The electrode is used to connect the electrode surface facing away from the electrolyte, thereby avoiding the danger of contact between the lead and the electrolyte, thereby simplifying the structure and assembly of the sensor. In other words, as long as the electrode, the conductive ring sheet, and the Teflon film to prevent the electrolyte from evaporating are stacked on the opening of the electrochemical cell, and the end cap is tightly fixed to fix the aforementioned component tightly ; As for the auxiliary electrode side is also made in the same way. With the above-mentioned models, not only the components used are quite small, but the assembly is extremely easy and convenient, which is more conducive to automated production. In addition, in order to achieve the above purpose, a silver wire whose surface is vaporized to vaporized silver is used as a reference electrode. In addition, and use water-absorbing glass in the electrochemical cell ____-5-This paper ^^^ __ ^^ is called the 8 size 4 (21 () / 297 mm) 533305 The good middle part «. ^-^ H_T 消贽 Cooperation * .print f Α7 Β7 V. Description of the invention (3) Glass fiber and membrane sheet so that the surface of each electrode can fully and uniformly contact the electrolyte. Therefore, the electrolyte capacity in the electrochemical cell does not need to be too much, that is, it is sufficient for long-term use. These and other objectives, features, and advantages of the present invention will be more apparent from the following description of preferred embodiments with accompanying drawings in more detail. _Brief Description of the Drawings Figure 1 is a sectional view of an exploded structure of an electrochemical gas sensor according to a preferred embodiment of the present invention. Fig. 2 shows the test results of the carbon monoxide detected by the gas sensor shown in Fig. 1. θ Symbol description 1 Sense cap 2, 1 5 Air inlet 3, 13 Teflon membrane 4, 12 Conductive ring 5 Sensing electrode 6, 10 Ring gasket 7 Electrochemical cell body 8 Reference electrode Open 9 electrolyte injection port 10 interference gas bottle 11 auxiliary electrode 14 auxiliary end cap 16 17 electrolyte and water-absorbing glass fiber reference electrode The examples are explained, but we should understand that they should only be used to exemplify the preferred structure of the present invention, but not to limit the present invention. The dimensions of this paper apply to Zhongguan) A Tiege (2ΐ〇χ297 公 楚) '----: -I ^ 搛! (Please read the notes on the back before filling this page) Order 533305 A7 B7
圖1顯示一根據本發明之較佳實施例而成之電化學型式 氣體感測為之分解剖面示意圖。如該圖所示，本發明所揭 電化學型式氣體感測器由上至下大體包含··一感測端帽頭 1、一電化學槽本體7、一輔助端帽頭14，以及依序夾於 感測端帽頭1與電化學槽本體7之間的透氣鐵氟龍膜3、導 電環片4、感測電極5、矽膠製墊片6，和對稱地依序夾於 電化學槽本體7與輔助端帽頭1 4之間的矽膠墊片1 〇、輔助 電極11、導電環片12、以及透氣鐵氟龍膜13。 其中，感測端帽頭1與輔助端帽頭i 4係由鐵氟龍材質或 是其它具較低表面吸附性及抗壓力的塑膠材質製成，且感 測端帽頭1之中心突出，中心並設有一進氣口 2，以供導入 待測試之目標氣體之用；輔助端帽頭1 4亦設有一氣體進氣 口 15。電化學槽本體7由塑膠材質製成，其兩端作成可供 感測端帽頭1與輔助端帽頭1 4嵌入其中，並夾持前述可容 納於其中之電極等組件的擴大開口槽（未標示符號）。另， 孩電化學槽本體7之内徑約9 m m，容量約爲1.2 m 1，且在 靠近感測電極端處開設有一小孔8，供***參考電極1 7之 用；且在本體中心處並設有一電解液注入口 9，供注入電 解液1 6之用。基本上，小孔8和電解液注入口 9在組裝該 感測器之各部構成時，係以環氧樹脂予以密封的。而電解 液1 6則以對應於目標氣體之電解液摻和吸水性破璃纖維所 構成。 此外，透氣鐵氟龍膜3和1 3亦可以具疏水性之透氣膜材 貝所作成，主要用以防止電解液之蒸發；導電環片4和1 2 _ —__ __二 Ί — 本纸張人度適用中园國家標準（CNS ) A4規格（210X297公釐） (請先閱讀背面之注意事項再填寫本頁)FIG. 1 is a schematic exploded cross-sectional view of an electrochemical type gas sensor according to a preferred embodiment of the present invention. As shown in the figure, the electrochemical gas sensor disclosed in the present invention generally includes, from top to bottom, a sensing end cap head 1, an electrochemical tank body 7, an auxiliary end cap head 14, and sequentially A gas-permeable Teflon membrane 3, a conductive ring sheet 4, a sensing electrode 5, a silicone gasket 6 sandwiched between the sensing end cap 1 and the electrochemical cell body 7, and sequentially sandwiched between the electrochemical cell A silicon gasket 10 between the body 7 and the auxiliary end cap head 14, an auxiliary electrode 11, a conductive ring sheet 12, and a breathable Teflon membrane 13. Among them, the sensing end cap 1 and the auxiliary end cap i 4 are made of Teflon material or other plastic materials with low surface adsorption and pressure resistance, and the center of the sensing end cap 1 protrudes. The center is also provided with an air inlet 2 for introducing the target gas to be tested; the auxiliary end cap 14 is also provided with a gas inlet 15. The electrochemical cell body 7 is made of plastic material, and the two ends of the electrochemical cell body 7 are made into which the sensing end cap head 1 and the auxiliary end cap head 14 can be embedded therein, and hold the aforementioned enlarged opening slot (such as the electrode and other components that can be accommodated therein) Unlabeled). In addition, the inner diameter of the electrochemical cell body 7 is about 9 mm, the capacity is about 1.2 m 1, and a small hole 8 is opened near the end of the sensing electrode for inserting the reference electrode 17; and at the center of the body An electrolyte injection port 9 is provided for the electrolyte 16 injection. Basically, the small hole 8 and the electrolyte injection port 9 are sealed with epoxy resin when the parts of the sensor are assembled. The electrolytic solution 16 is composed of an electrolytic solution corresponding to a target gas and a water-absorbing glass breaking fiber. In addition, the breathable Teflon membranes 3 and 1 3 can also be made of hydrophobic breathable membranes, mainly used to prevent the evaporation of the electrolyte; conductive ring sheets 4 and 1 2 _ —__ __ 二 Ί — paper Zhang Rendu applies the National Park Standard (CNS) A4 specification (210X297 mm) (Please read the precautions on the back before filling this page)
533305 A7 B7 好於部中央il^-XJh工消抡合作·ΐ卬^ 五、發明説明（ 則由銅環鍍金而成。感測電極5和輔助電極U基本上係由 含貴重金屬的觸媒燒結於多孔性碳紙基材上而製成一具孔 隙性之高表面積電極，例如，以_媒摻和碳粉燒結在多 孔性碳纸上，而多孔性碳紙之開孔率大約在π。〆 兩 在0.0 93 Qcm左右。矽膠製墊片6和1〇作成中空狀，二 別位於電化學槽開口與感測電極5和輔助電本川之間，用 以塾接並使電解液16與電極5和川目接觸。至於參考電梅 "則由之銀線將其表面加以氯化成爲氯化銀而 成，長度約15ffim，當然亦可單純由銀線構成。 基本上’根據本發明而成之電化學型式氣體感測器於組 裝時可借助簡單爽治具之使用，即能輕易將感測器組裝完 成。以下，即進-步就上述構成之電化學型式氣體感測器 4各構件組裝情形作_説明。首^’將摻和有吸水性玻璃 誠維在吸濕性膜片之輔助下，放置於電化學槽 本體7之中，然後即將該電化學槽本體置放於特製爽且^ (未圖^)，再依序將前述塾片6、感測電接5、導電環片 4、鐵氟龍膜3、以及感測端帽頭以在電化學槽本體之開 口槽中，*後以手壓機對該感測端帽頭丨二約 〇.5kg/cm2之壓力’即可輕易地將前述各组件緊密固定在 電化學槽本體7上。至於輔助電極端之組裝方式由於各構 件與感測電極端相對稱’因而以類似方式即可輕易+成。 藉由上述组裝方式，電解液將可以在不使用膠^劑之 下，輕易地藉由感測電極、導電環片、鐵氟龍膜以及感測 續中目頭卡人該電化學槽開口槽而被封裝在電化學 本纸張尺度ϋ财關緖準（CNS ) Α视格 (請先閱讀背面之注意事項再填寫本頁} 訂 533305 A7 B7 五、發明説明（6 ) 槽内。 以下’進一步就根據上述結構以及組裝方式完成之電化 子型式氣體感測器之測量方式以及動作原理作一説明。感 時’使待測之氧化性或還原性氣體，經由感測端帽體1 <進氣口2進入，且該氣體將進一步通過鐵氟龍膜3、多孔 性感測電極5、而與觸媒5 a及電解液丨6接觸。此時，藉由 控制參考電極17之電位，使感測電位固定於待測氣體之特 足氧化或還原電位，俾使待測氣體分子與觸媒和電解液在 二相介面下產生氧化或還原反應；在此同時，輔助電極亦 會產生對應之還原或氧化反應，進而在感測電極5與輔助 電極1 1 t間產生一反應電流；接著，藉由與該等電極5和 11相接觸t導電環片4和I2，由於靠近電解液端之作爲電 極基板之多孔性紙具有導電性，因而可以依序透過亦具導 電性之觸媒，而使電流流通於導電環片之間，如此一來該 反應電流即可被輸出而感測出一對應於電流大小之氣體濃 度了。其中，由於反應電流將與待測氣體之濃度成一線性 關係，因而由電流大小即可計算得到該待測氣體之濃度。 其次’爲顯示本發明所揭該電化學型式氣體感測器之效 果，特以一氧化碳氣體感測器爲例進一步説明其效能。在 此例下，氣體感測器之構造同前所述，然針對一氧化碳氣 m，特以1 . Ο Μ Η 2 S 0 4爲電解液，依此，一氧化竣氣體感 測器將在感測電極端產生如下式之氧化反應·· 2C0 十 2H20->2C〇2 + 4H + + 4e· 在此同時，輔助電極上將產生氧分子之還原反應如下： _________- 9 - >紙張尺度適州中國國家標準（〔阳）六4規格（210\ 297公楚)~~" -- (請先閲讀背面之注意事項再填寫本頁) •4533305 A7 B7 is better than the central ministry il ^ -XJh industry cooperation cooperation 五 ^ V. Description of the invention (they are made of copper ring gold plating. The sensing electrode 5 and the auxiliary electrode U are basically made of a catalyst containing precious metals Sintered on a porous carbon paper substrate to make a porous high-surface-area electrode, for example, sintered with porous carbon powder on porous carbon paper, and the porosity of the porous carbon paper is about π . The two are about 0.0 93 Qcm. Silicone gaskets 6 and 10 are hollow, and they are located between the opening of the electrochemical cell and the sensing electrode 5 and the auxiliary electric main, for connecting and making the electrolyte 16 It is in contact with electrode 5 and Kawame. As for the reference electric plum, the surface is made of silver chloride by chlorinating it to silver chloride, with a length of about 15 ffim. Of course, it can also be composed of pure silver wire. The invented electrochemical type gas sensor can be easily assembled by using simple and easy fixtures when assembling. The following is the step-by-step configuration of the above-mentioned electrochemical type gas sensor 4 The assembly of each component will be described. The first ^ 'will be mixed with a water-absorbing glass Chengwei is placed in the electrochemical cell body 7 with the aid of a hygroscopic membrane, and then the electrochemical cell body is placed in a special Shuang and ^ (not shown), and then the aforementioned cymbals 6 are sequentially , Sensing electrical connection 5, conductive ring sheet 4, Teflon membrane 3, and the sensing end cap to be in the opening slot of the electrochemical cell body, and then use a hand press to the sensing end cap 丨 II A pressure of about 0.5 kg / cm2 'can easily fix the aforementioned components tightly on the electrochemical cell body 7. As for the assembly method of the auxiliary electrode terminal, since each component is symmetrical to the sensing electrode terminal, it is similar in that With the above assembly method, the electrolyte can be easily used without the use of adhesives by the sensing electrode, the conductive ring sheet, the Teflon film, and the sensing head. The electrochemical cell is opened in an electrochemical cell and is enclosed in the paper size of the paper. The financial standard (CNS) Α Sight (Please read the precautions on the back before filling this page} Order 533305 A7 B7 V. Description of the invention (6) In the tank, the following further describes the type of electrochemical subassembly completed according to the above structure and assembly method. The measurement method and operation principle of the body sensor will be described. When sensing, the oxidizing or reducing gas to be measured is entered through the sensing cap 1 < air inlet 2 and the gas will further pass through the iron. Fluorine membrane 3, porous sensing electrode 5, and contact with catalyst 5a and electrolyte 丨 6. At this time, by controlling the potential of reference electrode 17, the sensing potential is fixed to the specific oxidation of the gas to be measured or Reduction potential, causing the gas molecules to be tested to oxidize or reduce under the two-phase interface; at the same time, the auxiliary electrode will also generate a corresponding reduction or oxidation reaction, and then the sensing electrode 5 and the auxiliary A reaction current is generated between the electrodes 1 1 t. Then, by contacting the conductive rings 4 and I2 with the electrodes 5 and 11, the porous paper as the electrode substrate near the end of the electrolyte has conductivity, so it can A conductive catalyst is sequentially passed through, so that a current flows between the conductive rings, so that the reaction current can be output and a gas concentration corresponding to the current can be sensed. Among them, since the reaction current will have a linear relationship with the concentration of the gas to be measured, the concentration of the gas to be measured can be calculated from the magnitude of the current. Secondly, in order to show the effect of the electrochemical gas sensor disclosed in the present invention, a carbon monoxide gas sensor is taken as an example to further illustrate its effectiveness. In this example, the structure of the gas sensor is the same as described above, but for carbon monoxide gas m, 1.0 Μ Η 2 S 0 4 is used as the electrolyte. Based on this, the gas sensor after the oxidation will be in the sensor. The oxidation reaction at the electrode end is as follows: 2C0 10 2H20-> 2C0 + 4H + + 4e At the same time, the reduction reaction of oxygen molecules on the auxiliary electrode is as follows: _________- 9-> Paper size Shizhou Chinese National Standard ([阳) 六 4 Specifications (210 \ 297 公 楚) ~~ "-(Please read the notes on the back before filling this page) • 4
、1T 533305 A7 B7 五、發明説明（ 4e" + 02 + 4H + ^2H2〇 (請先閲讀背面之注意事項再填寫本頁) 综合上述兩個半反應即構成整個電化學式氣體感測器之 全反應，如可以表示如下； 2 C Ο + Ο 2 2 C Ο 2 此一例子之實驗測試結果如圖2所示，基本上在通入 ⑽㈣之-氧化碳配製在空氣中之標準氣體後，其感應 電流爲2 3 5 μ A，亦即咸廯啻、、云ϊ 1心、應兒机大小可達〇.47uA/Ppm， 待將氣源拿掉，感測器即迅速回到零點，其反應速率 爲2 4秒。 综上所述，由於本發明_之電化學型式氣體感測器使 用不同於習知氣體感測器之結構、材料、以及組裝方式， 因而不僅具備良好之感測能力，並可使用最少之組件以及 快速之組裝方式，且其中之主要組件諸如電化學槽本體、 感測端帽頭、輔助端帽頭、以及環墊片等都易於使用模具 開模量產，將可大幅降低人力成本，且一旦達量產規模， 並能使用自動化量產’ m幅降低人力與製造成本。 又’ 2於以多孔性竣紙作料電基材，將使該等電極具有 相當高的表面積，而提高了量測時之敏感度。 因此’本案在提高效率與應用上，實爲-具有新穎性、 進步性與產業上利用性之發明。惟，雖已例舉本發明之一 較佳實施例作説明，然應了解的是各種對於熟於此技人士 顯而易知 < 變更與修改應都在以下所界定之申請專利範圍 中 〇 本紙張尺度適州中國國家標準（CNS ) A4規格（210x297公釐1T 533305 A7 B7 V. Description of the invention (4e " + 02 + 4H + ^ 2H2〇 (Please read the precautions on the back before filling this page) The combination of the above two half reactions constitutes the whole of the electrochemical gas sensor The reaction can be expressed as follows; 2 C 0 + 0 2 2 C 0 2 The experimental test results of this example are shown in Figure 2. Basically, after passing in a standard gas prepared by carbon dioxide in the air, The induced current is 2 3 5 μ A, that is, the salt water, cloud, 1 heart, and the size of the machine can reach 0.47uA / Ppm. When the air source is removed, the sensor will quickly return to zero. The reaction rate is 24 seconds. In summary, since the electrochemical gas sensor of the present invention uses a structure, material, and assembly method different from the conventional gas sensor, it not only has good sensing capabilities The minimum number of components and rapid assembly methods can be used, and the main components such as the electrochemical tank body, sensing end cap, auxiliary end cap, and ring gasket are easy to use for mold opening and mass production. Can significantly reduce labor costs, and Production scale, and can use automated mass production to reduce labor and manufacturing costs. Also, the use of porous porous paper as the electrical substrate will enable these electrodes to have a relatively high surface area and increase the measurement time. Sensitivity. Therefore, this case is really an invention of novelty, progress, and industrial applicability in improving efficiency and application. However, although a preferred embodiment of the present invention has been described as an example, it should be understood What is obvious to those skilled in the art < changes and modifications should be within the scope of the patent application as defined below. This paper size is in accordance with the Chinese National Standard (CNS) A4 size (210x297 mm)