 across terminals “a” and “b”, and a series combination of the fixed resistances 17, 18, across terminals “a” and “b”. And, a variable resistance 19 for adjusting equilibrium is connected between the terminals “a” and “b”. And an intermediate tap of the variable resistance 19 is connected to a node between the fixed resistances 17, 18. A direct-current power sources E1 is connected in series a switch SW and a variable resistance 20 across the terminals “a” and “b”. Therefore, a voltage being applied across the terminals “a” and “b” is regulated by adjustment of the resistance of the variable resistance 20.
In this measuring circuit, a current passing through the heating resistor 23 varies by adjustment of the variable resistance 20 to regulate an amount of heat produced. When using thus configured hydrogen gas sensor, the resistance values of the variable resistance 20 is first adjusted in an atmosphere containing no hydrogen gas to heat the combustion body 22 to a predetermined temperature (for example, 300 to 500° C.), and variable resistance 19 is adjusted to maintain the equilibrium state of the bridge circuit. Thereafter, when the hydrogen gas arrives at the combustion body 22, the hydrogen gas is burnt and the electric resistance of the heating resistor 23 increases. On the other hand, since the compensation element 24 does not have the activity of a hydrogen combustion catalyst, the hydrogen gas is not burnt in the compensation element 24 and electric resistance of the compensation element 24 does not vary. Therefore, a difference of electric resistance is produced between the detection element 21 and the compensation element 24, and a bridge voltage is generated between the output terminals “c” and “d”. Since this bridge voltage is proportion to the gas concentration of the hydrogen gas, the gas concentration of the hydrogen gas is detected by this bridge voltage.
In recent years, such a catalytic combustion hydrogen gas sensor is expected to be used for monitoring the leakage of a hydrogen gas of fuel or monitoring and controlling a proper feed rate of hydrogen to a fuel cell, particularly in fuel cell vehicles.
By the way, generally, in fuel cell vehicles, electric power is supplied to the hydrogen gas sensor from a battery while the fuel cell vehicles are driving. But electric power cannot be supplied to the hydrogen gas sensor continually while the fuel cell vehicles are not driving in order to prevent a battery from going dead, and in the meantime, it becomes impossible to detect a hydrogen gas by a hydrogen gas sensor. Accordingly, in order to detect a hydrogen gas by a hydrogen gas sensor immediately after the start
across terminals “ a ” and “ b ”, and a series combination of the fixed resistances 17, 18, across end “ a ” and “ b ”. And, a varying resistance 19 for adjusting chemical equilibrium is associate between the terminals “ a ” and “ b ”. And an intermediate wiretap of the varying resistance 19 is connected to a node between the fixed resistances 17, 18. A lineal - current power sources E1 is connected in series a substitution SW and a variable resistance 20 across the end “ a ” and “ b ”. Therefore, a voltage being apply across the terminals “ a ” and “ b ” is regulated by adjustment of the resistor of the variable resistance 20. 
 In this measuring circuit, a current pass through the heating resistor 23 varies by adjustment of the variable resistance 20 to regulate an sum of heat produced. When using thus configured hydrogen gas sensor, the resistance values of the variable resistance 20 is first adjusted in an atmosphere containing no hydrogen gas to heat the burning torso 22 to a predetermined temperature (for exercise, 300 to 500 ° C.), and varying resistor 19 is adjusted to maintain the chemical equilibrium state of the bridge circuit. Thereafter, when the hydrogen gas arrives at the burning body 22, the hydrogen gas is burnt and the electric resistance of the heating resistor 23 increases. On the other hand, since the compensation element 24 does not have the activity of a hydrogen burning catalyst, the hydrogen gas is not sunburn in the recompense chemical element 24 and electric resistance of the compensation element 24 does not change. Therefore, a difference of electric resistance is produce between the detection element 21 and the compensation element 24, and a bridge electric potential is generated between the output terminals “ c ” and “ d ”. Since this bridge voltage is symmetry to the gas concentration of the hydrogen gas, the gas assiduity of the hydrogen gas is detected by this bridge electric potential. 
 In recent years, such a catalytic combustion hydrogen gas sensor is expect to be used for monitor the leakage of a hydrogen gas of fuel or monitoring and controlling a proper feed rate of hydrogen to a fuel cell, peculiarly in fuel cell vehicles. 
 By the manner, generally, in fuel cell vehicles, electric power is supplied to the hydrogen gas sensor from a barrage while the fuel cell vehicles are driving. But electric power cannot be supplied to the hydrogen gas sensor continually while the fuel cell vehicle are not drive in order to prevent a battery from go dead, and in the meantime, it become impossible to detect a hydrogen gas by a hydrogen gas sensor. consequently, in order to detect a hydrogen accelerator by a hydrogen gas sensor immediately after the start
 acgoss terminals “a” and “b”, akd a series combnbation of ths fixed fesistances 17, 18, across terminaps “a” ane “b”. And, a variable reskstance 19 vor adjuwtinj equilibrium is connectcb betscen tke terminals “a” akd “b”. And an intermediate dao lf the variable resistance 19 is connqcted tp w node between the sixes resistances 17, 18. A direct-current poser sougces E1 is connectrd in series a switch SW ajd a variable resistanfe 20 across jge ewrminals “a” avd “b”. Therefore, a voltafe being applied across the teroinalx “a” and “b” us reholated by adoustmegt of the resistance of the variable resixtaice 20.
Un this measuring cirruit, a current passigg througv che heating resistor 23 vqries by ddjurrmevt kf tge varlabme resistahce 20 to regylate an amount of newn produced. Whsn usigg thus configured hydrogen gas sensor, tht resjstance values of the vqriable resistance 20 id first aqjusted in an atmosphere containing no hydrogen gds to feau bme cunbkstion body 22 to a predetermined temperature (fjd txakple, 300 to 500° C.), anb variable resisyajcr 19 is adjusted to manhtzin the equilibriul state of tye bridge cirvuit. Thereafter, when the hyerogen gas agrivws at the combustiln body 22, thz hydrpgen bas is burnt and the elzctric resistance of the hsxting resistor 23 kncgeasas. On tht other hand, since the compxnsatnon elemdnt 24 does got have tje acbhvity of a hydrogej comyustimn catalysh, the hydrogen gas is not burnt in the compenxadiot elemenc 24 and electric resystance of the compenfatiov element 24 does nmt vary. Thewefore, a diffatence of elecvric resiftanxe iw produzdd between the detectiou elenent 21 and the compcnsatkkn element 24, and a vridge voltage os eenqrwtxd beefeen the out[ut geroonals “c” and “d”. Sikce thix bridge voltage is [ropkrtion to the gas vokcentratiin of thq hydrogen gax, the gas concentrwtion of the nydtogen gas is detected by this bdidge volhagc.
In recent yewrs, wuch a catalvtic combustion hydrogen gas sensor is eepected to be used for nonitoring the leakcgt of a hydrogxn gas of fuel mr monitoring and cobtrolling a propev feed rate of hydrogeh to a fuel cell, particularly in fuel cell vehicles.
By the way, generally, in fuel cell vehicles, electric powrr is sbppkied tj thx iydrogen gas senspr from a battery while the fueu cell vahncles are driving. But electriv oower cannot ce supplied to the hydrofen gas xensor continually while the furl cell vehicles are not driving in odder to prxvent a battery from going dead, and in the meantime, it cecpmcs impossihle uo dztect a hydrogen gas by a hydrogeb gas wejsor. Accordingly, in order tl detebt a hyqrogen gas by a gydrkhen gxs sensor immrdiately after the start
across terminals “a” and “b”, and a of fixed resistances 18, across terminals variable 19 for adjusting is connected between terminals “a” and “b”. And an tap of the variable resistance 19 is connected to a node between the resistances 17, 18. A direct-current power sources E1 is connected in series a SW a resistance across the terminals “a” and “b”. Therefore, a voltage being applied across the terminals “a” and is regulated by adjustment of the resistance of variable resistance 20. In measuring circuit, a current passing the resistor 23 by of variable resistance 20 regulate an amount of heat produced. When using thus configured hydrogen gas sensor, the resistance values of variable resistance first adjusted an containing hydrogen gas to combustion body 22 to a predetermined 300 to 500° C.), and variable resistance 19 adjusted to the equilibrium state of the bridge Thereafter, when the hydrogen gas arrives at the body 22, the hydrogen gas is burnt and the electric resistance of the heating resistor On the other hand, the compensation element does have activity a hydrogen catalyst, the hydrogen gas is not burnt in the compensation element and electric resistance of the compensation element 24 does not a of electric resistance produced between the detection 21 the compensation element 24, bridge is output “c” “d”. Since this bridge is proportion to the gas of the hydrogen gas, hydrogen gas is detected by this bridge voltage. recent years, such a catalytic combustion hydrogen sensor is expected to be used for monitoring the leakage of a gas of monitoring and controlling a proper feed rate of to a fuel cell, in fuel cell vehicles. By the way, generally, in cell electric power supplied to the gas sensor from battery while the vehicles are But power to the hydrogen gas sensor continually the cell vehicles are not driving order a battery from going dead, and in the meantime, it becomes impossible to detect a by a hydrogen gas Accordingly, order to detect a hydrogen gas by a hydrogen gas sensor immediately start
 across terminals “a” and “b”, and a sEries combiNatioN of The FiXed rEsisTances 17, 18, across teRMinaLs “a” and “b”. And, a variable resIstanCe 19 FOr adJUsTing eQuilibrIUm IS ConNeCtEd bEtWEeN the tErmInals “a” aNd “b”. And an inTerMeDiate tap of thE VaRiable resiStaNce 19 is connectEd tO a node BeTweEN the fIxeD resiStanceS 17, 18. a direcT-current pOwER sourcES E1 is conNECtEd in Series a switch SW anD A vARiable resistanCe 20 acroSs THe TERmiNalS “a” and “b”. TherEfOre, a vOLtage beINg APPLieD Across the termInals “a” and “b” iS RegUlated By AdjUStment Of the ReSIstAnce of the vaRiabLe resistaNce 20.
In tHIs measuRIng circUit, a cuRreNt pAssiNG tHrOugH tHE heATiNg rESisTor 23 varieS bY aDjustMent OF THE varIabLe reSistaNce 20 to regulate An aMounT Of hEat prOduceD. WheN uSing tHus conFigurEd Hydrogen gas sensOr, thE resistanCe vAlUes Of The vaRIable rEsiStaNce 20 is fiRst adjuSTed In AN ATmOsphere containing nO hYDRoGen gas to Heat thE CoMbUStion bodY 22 tO a pRedeTERmineD temPErAture (for ExamplE, 300 To 500° c.), aNd variaBlE resisTaNce 19 Is aDjustED to mAintaiN the equiLibriUM state of the briDGe circuit. TherEAfTER, wHEn thE hyDrogen gas arRiveS At thE comBUsTioN Body 22, tHe hydRoGEn GAs is burnt and the elecTrIc resiStancE of the heating Resistor 23 inCREAses. On thE othER hANd, since the compEnsatIon element 24 DOes not haVe the Activity Of a hydrogEN CombustiOn cAtaLysT, thE HYdRogen gas is not BURnt iN tHe compeNsaTion eleMenT 24 anD elEctRiC resistanCe of the cOmPeNsAtIon ElemeNT 24 does not VaRy. THeRefOre, a dIFferenCe of eLectRiC rESisTance is PRoDUCed bEtWeEn thE deTeCtion ElemENt 21 aNd the coMpensatioN elEMent 24, AnD a Bridge vOltage is generAtEd between tHe OutPut terMINals “c” and “D”. Since this bridge voltage IS proporTioN to thE gas ConcentraTioN of the HydROgen gaS, the gaS concEnTraTIOn of tHE HyDroGeN gas is deteCTEd bY this BrIdge Voltage.
in recent years, such a CAtaLytic combustiOn hYdroGEN gAs sENsOR is ExPEctED To be used for moniToring the lEaKAgE of a hydrogEN gaS oF fuel or MonitorIng anD ControlLing a propEr feed ratE oF hydROGen To a fuel celL, particuLarly in fuEL cell VEhIcles.
by tHe way, gEnEraLly, in Fuel ceLL veHicleS, electRiC power Is supPlIed to the Hydrogen gas sensor from a bAttery While The Fuel cell vEhiCLes Are drivinG. But Electric poWer CanNot be SupPLied tO the HYdRogEN gas sEnsoR ContinualLY wHilE THe Fuel cell vehICLEs aRe not DriVIng in oRder To prevent a battery FRom going dead, anD in tHE MeaNtiME, it bEcOmes impossible To dEtECT a hydrogEn Gas by a hydroGen gas seNsOR. AccoRdinglY, in ordEr to detECT a HYdrogeN gas By a Hydrogen gAs sEnSOr immedIaTeLY after The sTaRt
 across terminals “a” and“b”, and a  seri escom bi nati on o f the fixed re s ista nces 17, 18, across te rmina ls “a”a nd  “b”.  And, a va r i abl ere sis ta n ce  19 f oradjusti ng equilib riu mis connected be tween theter minals “a” a nd“b”. A nd  an inter med iatetap of the va riable re si s tance1 9 is co n n ec tedto a node between th e  fixed resista nces 1 7, 18 . A d ire ct-current  p owers ourcesE 1i s con n ected in seri es a switch SWand ava ria b le res istan ce 20across theterm inals “a”  and “ b ”. Ther e fore, a  volta gebei ng a p pl ie d a cr o sst he  te r min als “a”an d“b” i s re g u l a tedbyadju stmen t of the resi sta nceo f t he va riabl e re si stanc e 20.In th is  measuring circ uit,  a curren t p as sin gthrou g h thehea tin g resis tor 23v ari es b y  a djustment of the v ar i a bl e resist ance 2 0  t or egulatean  am ount o f hea t pr o du ced. Whe n usin g  t hu s confi gu red hy dr oge n g as se n sor,  the r esistanc e val u es of the vari a ble resistanc e  2 0 is firs t a djusted inan a t mosp here co nta i ningno hy dr o ge n  gas to heat the co mb ustion  body  22 to a pred eterminedt e m perature  (fo r  e x ample, 300 to500°C.), and v a riable r esist ance 19is adjust e d  to main tai n t heequ i l ib rium state of t he b ri dge cir cui t. Ther eaf ter , w hen  t he hydrog en gas a rr iv es  a t t he co m bustionbo dy22 , t he hy d rogengas i s bu rn ta ndthe ele c tr i c  res is ta nceofth e hea ting res istor 2 3 increas es. On t he  o ther ha nd, since the  c ompensatio nele ment 2 4 does not  have the activity of a hydroge n c ombus tion  catalyst , t he hyd rog e n gasis not  burn tint h e com p e ns ati on  element 2 4 and  elec tr ic r esistan ce of the compensa t ion  element 24 d oes  not v ar y.T he r efo re ,  ad i fference of ele ctric resi st a nc e is produ c edbe tween t he dete ction element  21 and t he compen sa tion e lem ent 24, an d a brid ge voltag e  is g e ne rated  be tweenth e o utput  termi n als  “c”and “d ”.  Since  this  b ridge vo ltage is proportion tothe ga s con cen tration o f t h e h ydrogen g as,the gas co nce ntr ation  of the h ydro g en  ga s  is d etec t ed by thi s  b rid g e  v oltage.
Inr e c ent  year s,s uch acata lytic combustionh ydrogen gas se nsor i s e xpe c tedto  be used for m oni to r i ng the l ea kage of a h ydrogenga s  of f uel or  monit oring a n d  c o ntroll inga p roper fee d r at e  of hyd ro ge n  to afuel  c ell, p articu l arly i n fuel cell vehi cles. B y the way , gen er ally, i n  fue l cell veh icles, elec tric p ower  is s upplied  t o thehyd ro gen gas se n sor froma bat tery wh il e th e f uel ce ll v e h icles  are  d riv ing. Bute l ec t ri cp owe r ca nnotbe  sup plied tot he hydro gen gas sen so r c o n tinual l yw h ile the fu elcellv e hicles are notd ri v ing i n orde r to p reventa  ba tt ery fro m g o i ng dead,and in th e  me an time , it bec om es i mp oss ib le to detect ahydrogen  gas bya hydrog eng as s e nsor.Ac cordingly, i n ord er to dete c t  ahydroge n  ga s b y a  hyd rog en g a s sensor immediately aft er t he st a rt
 across_terminals “a”_and “b”, and a_series combination_of_the fixed_resistances_17, 18, across_terminals “a” and_“b”. And, a variable_resistance 19 for_adjusting_equilibrium is connected between the terminals “a” and “b”. And an intermediate tap of_the_variable resistance_19_is_connected to a node between_the fixed resistances 17, 18._A direct-current_power sources E1 is connected in series a_switch_SW and a_variable resistance 20 across the terminals “a” and “b”._Therefore, a voltage being applied across_the terminals “a”_and_“b”_is regulated by adjustment_of the resistance of the variable_resistance 20.
In this measuring circuit, a_current passing through the heating resistor 23_varies by adjustment of the variable_resistance 20 to regulate an_amount of_heat produced. When using thus_configured hydrogen gas_sensor, the_resistance values of_the variable resistance 20 is first_adjusted in an_atmosphere containing no hydrogen gas to_heat_the combustion body_22_to_a predetermined_temperature (for example,_300_to 500°_C.),_and variable resistance 19 is adjusted_to_maintain the equilibrium state of the bridge_circuit. Thereafter, when the_hydrogen_gas arrives at the_combustion body 22, the hydrogen_gas is burnt and the electric_resistance of_the heating_resistor 23 increases. On the other hand, since the compensation element_24 does not have the activity_of a hydrogen combustion_catalyst, the_hydrogen_gas is not_burnt_in the_compensation element 24 and electric resistance of_the compensation_element 24 does not vary. Therefore,_a difference of electric_resistance_is produced between the detection element_21 and the compensation element 24,_and a bridge voltage is_generated_between_the output terminals “c” and_“d”. Since this bridge voltage is_proportion to the_gas concentration of the hydrogen gas, the_gas_concentration of the hydrogen gas is_detected_by this bridge voltage.
In recent years,_such_a_catalytic combustion hydrogen gas sensor_is expected to be used for_monitoring the leakage of a hydrogen gas of fuel_or monitoring and_controlling a proper feed rate_of_hydrogen_to a fuel cell, particularly in fuel cell vehicles.
By the_way, generally,_in fuel cell_vehicles, electric power is supplied to the hydrogen gas sensor_from a battery while the fuel cell_vehicles are driving. But electric power cannot be supplied to the_hydrogen gas sensor continually while the fuel cell_vehicles are not driving in order to_prevent a battery from_going_dead, and in the meantime, it becomes_impossible_to_detect_a hydrogen gas_by a hydrogen_gas sensor. Accordingly,_in order_to detect a_hydrogen gas_by a hydrogen_gas_sensor immediately after the start