CIRCUIT OF IMPROVED NITRIC OXIDE RESPONSE FOR GAS ANALYZER Cross Reference Related Request This application claims the benefit of the provisional patent application of the US. No. 60 / 059,523, filed September 22, 1997. BACKGROUND OF THE INVENTION The present invention relates in general to test and diagnostic equipment for testing motor vehicles, particularly vehicles energized by internal combustion engines. The invention has particular application to diagnostic equipment that incorporates gas analyzers, to analyze exhaust emissions from internal combustion engines, and even more specifically to nitric oxide (NO) detector circuits for these gas analyzers. The present invention is an improvement of a NO detection circuit of the type employed with a diagnostic system, such as that sold by Sun Electric and known as the Service Inspection System. This system includes a module of infrared shelf structure (IR) that includes a bank of non-dispersive infrared optics (NDIR = non-dispersive infrared) that detects the concentration of hydrocarbons, carbon monoxide, carbon dioxide and other gases within the system of vehicle exhaust gases. The NDIR optics bank includes optional input / output circuits and peripheral transducers for additional power supplies, including a NO supply. There are government regulations that establish specifications for the performance of engine diagnostic equipment and in particular emission analyzers. Among these specifications is a response time specification for certain constituent gas detectors. The specifications essentially require that the detector output reach a certain percentage of a nominal output reading within a certain period of time, for example within four or five seconds, the specified period of time varies with the ambient temperature at which it is performed. the proof. Applicants have found that when the NO detector is used in the emission analyzer, its response times, that is, the times of rise and fall of the detector output, may exceed the specifications established by government regulations, particularly at low levels. ambient temperatures. Applicants have attempted to heat the NO detection cell, such as a resistive heater, but the heater does not decrease the response times sufficiently to meet the specifications. SUMMARY OF THE INVENTION A general objective of the present invention is to provide an improved fluid constituent detection apparatus, which avoids the disadvantages of the previous apparatus while producing additional operational and structural advantages. An important feature of the invention is the provision of a detection circuit for a gas constituent that provides relatively fast response times. In connection with the above feature, another feature of the invention is to provide a detection circuit of the established type, which does not require any auxiliary heating. Still another feature of the invention is to provide a detection circuit of the established type that responds to temperature, in order to alter circuit operation depending on the ambient temperature. Certain of these and other features of the invention can be achieved by providing an apparatus for analyzing exhaust emissions from an internal combustion engine, comprising: a transducer structure that includes a detector that responds to nitric oxide in the emissions to generate a signal of electrical output, a processor and a response enhancer circuit, adapted to be coupled between the transducer structure and the processor to reduce the response time of the detector. Other features of the invention can be achieved by providing a fluid constituent detection apparatus, which comprises: a transducer that responds to a predetermined constituent of a fluid to generate an electrical output signal, a response improvement circuit adapted to be coupled to the transducer to reduce the response time of the transducer and a switching mechanism having a first condition for electrically connecting the response improvement circuit to the transducer and a second condition for electrically disconnecting the response improvement circuit from the transducer. Still other features of the invention can be achieved by providing a method for detecting a constituent gas in the exhaust emissions of an internal combustion engine, comprising: exposing the emissions to a constituent transducer, to produce an electrical output signal indicative of the presence of the constituent gas, detecting the ambient temperature and improving the output of the transducer only below a predetermined ambient temperature. The invention consists of certain novel features and a combination of parts which will now be fully described and illustrated in the accompanying drawings, it being understood that various changes in the details may be made without departing from the spirit or sacrificing any of the advantages of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS In order to facilitate an understanding of the invention, illustrated in the accompanying drawings, a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, the invention, its construction and operation and many of its advantages, should be easily understood and appreciated. Figure 1 is a partial schematic and partially functional diagrammatic block view of a gas analyzer for a service inspection system of the type with which the present invention is intended to be used; Figure 2 is a block diagram of a relevant portion of the gas analyzer of Figure 1, illustrating the location of the detector response control circuitry of the present invention; Figure 3 is a schematic diagram of the detector response control circuit of the present invention; and Figures 4 and 5 are graphs illustrating the effect of the response control circuit of Figure 3. DESCRIPTION OF THE PREFERRED MODE With reference to Figure 1, a detector or transducer structure of an exhaust analyzer of the prior art 10, of the type with which it is intended to employ the present invention, including an optical IR bank 35 and a nitric oxide cell 30, which is an electrochemical cell sensor or transducer and produces an electrical output indicative of the amount of nitric oxide in the gas sample. More specifically, the optical IR bank 35 includes gas sample tubes 11, 12 and 13 which respectively can be designed to detect carbon monoxide (CO), hydrocarbons (HC) and carbon dioxide (C02). The sample tube 12 communicates with each of the other sample tubes 11 and 13, and the sample tube 11 also communicates with a gas inlet conduit 14, which is adapted to be coupled to receive the exhaust emissions from a associated internal combustion engine (not shown) under test, while the sample tube 13 is coupled to a gas outlet conduit 15. The sample tubes 11-13 respectively are provided with infrared (IR) sources 16 to 18, located respectively at one end of the tubes 11-13 for radiating infrared energy through the tubes, the sources 16 to 18 are coupled to an associated DC voltage source Vcc through a switching structure 19 operated by a control circuit of switching 19a. Preferably, IR sources 16-18 are controlled by duty cycle (periodic cut) to provide a reference state of ON / OFF for each detector. The optical bank IR 35 also includes an optical detector / filter structure 20, which includes 3 detectors 21, 22 and 23 respectively that are provided at the ends of the sample tubes 11-13 opposite the IR sources 16-18 and four filters associated optics 24 to 27. More particularly, the sample tubes CO and C02 11 and 13, respectively have optical filters 24 and 27, while the sample tube 12 has optical filters, a reference filter 25 and a HC 26 filter. It will be appreciated that the gases within the sample tubes 11-13 absorb the IR energy as it passes, and the detectors convert the received IR energy into an output and voltage signal, which is periodically cut off because the Feed to IR sources is subjected to periodic cutting. The output of the optical filters 24-27 is applied through an amplifier circuit 28 and after digital conversion at 29, they are applied to a microprocessor 34 that analyzes the output signals and also regulates the switching control circuit 19a. The output of the cell NO 30 is also provided to the amplifier circuit 28 of the optical bank IR 35. It is a fundamental aspect of the present invention that a response control circuit 14 is interposed between the NO 30 cell and the optical bank IR 35 as illustrated in Figure 2. The details of the response control circuit 40 are illustrated in Figure 3. The NO 30 cell has an inlet duct 31, which communicates with the gas inlet duct 14, and generates an electrical output signal indicative of the presence of a nitric oxide constituent in the input emission gases, this output is also applied to the amplifier circuit 28 as a "NO ENTRY" (NO IN) signal. The optical bank NDIR 35 also includes a temperature sensor 32 and a pressure detector 33 coupled to the gas outlet conduit 15 and produces electrical output signals which in turn are coupled to the amplifier circuit 28. Preferably, the amplifier circuit 28 and the switching control circuit 19a are located on an analog printed circuit board 36, while the analog-to-digital conversion circuits 29 and the microprocessor 34 are located on a digital printed circuit board 37 In accordance with the present invention, the NO (NO IN) signal of the NO cell is applied to the response control circuit 40, the output of which is designated "NO OUT" (NO OUT). amplifier circuit 28 on the analog PCB 36. With reference to Figure 3, the response control circuit 40 includes a response improvement circuit 41. In particular, the NO (NO IN) signal from cell NO 30. , it is applied through a parallel RC circuit, including a resistor 42 and a capacitor 43, to the non-inverting supply of an operational amplifier (op amp) 44, which can be a TLC252C, this supply is also connected through a resistor 45 a tie rra The output of op amp 44 is connected through a resistor 46 to its reversing output, this supply is also connected through a resistor 47 to ground. The output of op amp 44 is also connected through a resistor 48 to a feed (S8) of an analog multiplexer 50, which may be an ADG508A. The NO (NO IN) signal is also connected directly to the SI feed of the multiplexer 50, these two feeds are respectively connected to the NO OUT terminal D of the multiplexer 50 through circuit paths normally open 51 and 52, the selection of which path is closed is determined by the signals in the AO, Al and A2 feeds. The multiplexer 50 also has an activation power connected through a resistor 53 to a +5 VDC supply and feeds VSS and VDD connected respectively to the V- and V + supplies. In this way, it will be appreciated that the R-C circuit that is provided by the resistor 42 and capacitor 43 is normally connected to the NO OUT output. In operation, the RC circuit provides a time constant and the resistor 42 cooperates with the resistor 45 to provide a voltage divider, these circuits serve to reduce the rise and fall times of the NO 30 cell response. the voltage reduction in the op amp supply 44, by reason of the voltage divider, the op amp 44 cooperates with the resistors 46 and 47 to provide a convenient amplification, preferably approximately 1.15. A control circuit responsive to temperatures 60, for multiplexer 50 includes an op amp 61, which may be an LM 311, configured as a comparator, having its non-inverting feed connected to the junction between resistors 62 and 63A in a voltage divider, which is connected between earth and the cathode of a Zener diode 63, the anode from which it is grounded. The cathode of the Zener diode 63 is also connected through a resistor 64 to the +5 VDC supply. The op amp comparator 61 output is connected to its non-inverting supply via a resistor 65. The resistor 62 establishes a reference voltage level corresponding to a predetermined ambient temperature level which may be approximately 26.7 ° C (80 °). F). The inverter supply of the comparator 61 is connected to a temperature detector 66, which detects the ambient temperature and outputs an electrical signal indicative of that temperature. The reversal and non-inverter supplies of the op amp 61 are also respectively connected to ground through capacitor filters 67 and 67a. When the detected ambient temperature exceeds the reference temperature level, the comparator switches to produce an output signal, applied through a resistor 61 to the AO, Al and A2 feeds, of the multiplexer 50 to switch its condition, in this way opening path 51 and closing path 52, so that the NO (NO IN) signal is connected directly to the NO OUT terminal, in this way effectively removing the response improvement circuit 41 from the circuit. This switching will also be visually indicated by illumination of an LED 68, which is energized from a +5 VDC supply through a voltage divider 69 which is provided by the resistors 69a and 69b. The +5 VDC supply is obtained from a voltage regulator 70, which can be an LM7805. Supply voltages V + and V- are provided from an external source and are applied to op amp 44 and multiplexer 50, and supply V + is applied to op amp 61, all these supplies are provided with convenient bypass capacitors. In operation, the response improvement circuit R-C 41 serves to reduce the rise and fall times of the response of the NO 30 cell to levels that are well below the specifications that are provided by the relevant government regulations. However, it has been found that, at ambient temperatures above a certain level, typically approximately 26.7 ° C (80 ° F), the improvement in response time that is provided by the RC network is unnecessary and can undoubtedly result in overvoltage of the desired output voltage level of the detector circuits. In this way, the control circuit 60 serves to automatically withdraw the RC network from the response control circuit 40, when the ambient temperature reaches the predetermined temperature level and will likewise switch back to the circuit when the ambient temperature falls below the level predetermined. Now with reference to Figure 4, a waveform 75 representative of the response of the NO 30 cell without the improvement circuit of the present invention is illustrated. The waveform 75 has an ascent portion 76, which rises from an initial value of -2 volts to a maximum output value of approximately +1.8 volts, ie a total rise of 3.8 volts. Similarly, after disconnection of the exhaust gas emissions, the response falls back to the initial 0 emission level during a descent period 77 of the waveform. The rise time of waveform 75 is calculated as the time required to ascend from the starting point of emissions 0 to 90 degrees of the maximum output value, while the decay time is the time required to fall from the value maximum output to approximately 10% of that value. The rise time is indicated in Figure 4 as the time from ti to t2, which is calculated as 7,072 seconds, while the decay time from t3 to t4 is calculated at 5,576 seconds, with all the measurements taken at 4.4 ° C (40 ° F). With reference to Figure 5, the corresponding waveform 75A using the response improvement circuit of the present invention is illustrated. In this case, the rise portion 76A of the waveform has a rise time from ti to t2 calculated at 2,416 seconds, while the drop portion 77A has a decay time from t3 to t4 calculated at 3.126 seconds. In this way, the response time of the NO cell has been reduced by almost half by the use of the present invention. In a construction model of the present invention the op amp 44 can be a TLC252 CP, the op amp comparator 61 can be an LM311, the Zener diode 63 can be an LM336, the temperature detector 66 can be an LM34C, and the voltage regulator 70 can be a 7805. It will be appreciated that the values of resistors 42 and 45-48 and capacitor 43 will vary depending on the amount of acceleration of the NO cell response that is required. Similarly, the values of the components of the control circuit 60 will vary depending on the ambient temperature at which switching is desired. From the foregoing, it can be seen that gas detector circuits have been provided which provide an improved response time and automatically withdraw the best when not required. While particular embodiments of the present invention have been illustrated and described, it is evident to those skilled in the art that changes and modifications can be made without departing from the invention in its broader aspects. The matter set forth in the foregoing description and the accompanying drawings is offered by way of illustration only and not as a limitation.