figaro product information applications: features: tgs 3870 - for the detection of both methane and carbon monoxide the figure below represents typical sensitivity characteristics, all data having been gathered at standard test conditions (see reverse side of this sheet). the y-axis is indicated as sensor resistance ratio (rs/ro) which is defined as follows: rs = sensor resistance in displayed gases at various concentrations ro = sensor resistance in 3000ppm of methane * combination methane and carbon monoxide detectors tgs 3870 is figaro's new metal oxide semiconductor gas sensor for the detection of both methane and carbon monoxide. using a micro-bead gas sensing structure, both methane and carbon monoxide can be detected with a single sensor element by periodic application of two different heater voltages (high and low). miniaturization of the gas sensing bead results in a heater power consumption of only 38mw (average). tgs 3870 has low sensitivity to alcohol vapors (a typical interference gas in the residential environment) and has high durability, making the sensor ideal for consumer market gas alarms. * miniature size and low power consumption * high sensitivity and selectivity to both methane and carbon monoxide (co) * low sensitivity to alcohol vapor * long life and low cost sensitivity characteristics (methane): important note: operating conditions in which figaro sensors are used will vary with each customers specific applications. figaro strongly recommends consulting our technical staff before deploying figaro sensors in your application and, in particular, when customer s target gases are not listed herein. figaro cannot assume any responsibility for any use of its sensors in a product or application for which sensor has not been specifically tested by figaro. the figure below represents typical sensitivity characteristics, all data having been gathered at standard test conditions (see reverse side of this sheet). the y-axis is indicated as sensor resistance ratio (rs/ro) which is defined as follows: rs = sensor resistance in displayed gases at various concentrations ro = sensor resistance in 100ppm of co sensitivity characteristics (co): 0.1 1 10 100 10 100 1000 10000 methane hydrogen co air rs/ro gas concentration (ppm) 0.1 1 10 100 1000 10 100 1000 10000 100000 methane hydrogen co air rs/ro gas concentration (ppm)
structure and dimensions: basic measuring circuit: rev: 12/05 the sensor requires two voltage inputs: heater voltage (v h ) and circuit voltage (v c ). the sensor has three pins: pin #3- -heater (+), pin #2--sensor electrode (+), and pin #1--common (-). to maintain the sensing element at specific temperatures which are optimal for sensing two different gases, heater voltages of 0.9v and 0.2v are alternately applied between pins #1 and #3 during a 20 second heating cycle. circuit voltage (v c ) is applied between both ends of the sensor (rs) and a load resistor (r l ), which are connected in series, to allow measurement of voltage (v rs ). circuit voltage (vc) should be applied only at the moment when the signal is taken from the sensor. please refer to the document "technical information for TGS3870" for details regarding the timing and application of vc and v h . specifications: bottom view top view side view the value of power dissipation (p s ) can be calculated by utilizing the following formula: p s = sensor resistance (rs) is calculated with a measured value of v rs by using the following formula: r s = x r l (v rs ) 2 r s sensor r s r h v h v c (+) (-) v rs (+) (-) 1 3 2 r l basic measuring circuit 0.25 0.05 5.0 0.5 0.8 0.1 2.54 0.2 13.0 0.5 top view side view bottom view pin connection: 1: common(-) 2: sensor electrode(+) 3: heater(+) f 9.2 0.2 f 8.1 0.2 unit:mm 1 2 3 r e b m u n l e d o m0 7 8 3 s g t e p y t t n e m e l e g n i s n e sd a e b - o r c i m e g a k c a p d r a d n a t s d n a e s a b c i t s a l p n a c l a t e m s e s a g t e g r a t e d i x o n o m n o b r a c d n a e n a h t e m e g n a r n o i t c e t e d l a c i p y t m p p 0 0 5 2 1 ~ 0 0 5 - e n a h t e m m p p 0 0 0 1 ~ 0 5 - e d i x o n o m n o b r a c t i u c r i c d r a d n a t s s n o i t i d n o c e g a t l o v r e t a e h v h v h h v 9 . 0 = . c e s 5 , % 3 v l h v 2 . 0 = . c e s 5 1 , % 3 e g a t l o v t i u c r i c v c 0 . 5 e s l u p c d v 2 . 0 ) 0 7 8 3 s g t r o f n o i t a m r o f n i l a c i n h c e t o t r e f e r ( e c n a t s i s e r d a o l r l k 5 7 . 0 > ( e l b a i r a v w ) l a c i r t c e l e s c i t s i r e t c a r a h c t s e t d r a d n a t s r e d n u s n o i t i d n o c e c n a t s i s e r r e t a e h r h 3 3 . 0 w . p m e t m o o r t a r e w o p r e t a e h n o i t p m u s n o c p h w m 0 2 1v h h c d v 9 . 0 = w m 1 1v l h c d v 2 . 0 = w m 8 3e g a r e v a e c n a t s i s e r r o s n e s s r k 5 . 3 ~ 5 3 . 0 w e n a h t e m m p p 0 0 0 3 n i k 4 2 ~ 8 . 1 w o c m p p 0 5 1 n i y t i v i t i s n e s ) s r f o o i t a r e g n a h c ( b 5 6 . 0 ~ 0 5 . 0 h c s r 4 m p p 0 0 0 3 h c s r 4 m p p 0 0 0 1 6 . 0 ~ 1 . 0 m p p 0 0 3 o c s r m p p 0 5 1 o c s r t s e t d r a d n a t s s n o i t i d n o c s n o i t i d n o c s a g t s e t r i a n i s a g t e g r a t 0 2 t a 5 6 , c ? 2 h r % 5 s n o i t i d n o c t i u c r i c v h h v 9 . 0 = . c e s 5 , v % 2 v h l v 2 . 0 = . c e s 5 1 , v % 2 v c 0 . 5 = e s l u p c d v 2 0 . 0 ) 0 7 8 3 s g t r o f n o i t a m r o f n i l a c i n h c e t o t r e f e r ( t s e t e r o f e b d o i r e p g n i n o i t i d n o c 3 s y a d 5 (v rs - 0.5v h ) (vc-v rs ) caution : do not apply a constant circuit voltage (5.0v) or the sensor would not exhibit its specified characteristics. figaro engineering inc. 1-5-11 senba-nishi mino, osaka 562 japan phone: (81)-727-28-2561 fax: (81)-727-28-0467 www.figaro.co.jp email: figaro@figaro.co.jp
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