Abstract:
Described is a method and a device for more accurate measurement of a gas supply with a gas meter. A consumption-weighted correction factor is determined by weight averaging of a sensor error factor of the gas meter with a consumption profile characteristic of the gas supply location and the measuring signal is converted using the correction factor. Embodiments relate inter alia to: operation of the gas meter as volume, mass or energy meter; formulae for determining the correction factor with sensor error factors and consumption profiles relative to volume, mass or energy; and measuring signal correction in the case of a non-registering or registering gas meter. Advantages are inter alia: subsequent customer-specific measuring signal correction; no additional measuring complexity; and improved measuring accuracy, in particular improved energy measurement by means of compensation for inherent deviations of the energy signal in the vase of heat value variations.

Description:
TECHNICAL FIELD 
   The present invention relates to the field of gas supply measurement with through-flow sensors and in particular thermal through-flow sensors. 
   BACKGROUND INFORMATION 
   A gas meter which is calibrated as an energy measuring device is disclosed in WO 01/96819 A1. The calibration is based on the fact that sensor signal values are determined dependent upon the through-flow rate of a calibration gas and are stored in the gas meter in the form of a sensor calibration curve. The sensor calibration curve or the sensor signal values are multiplied by a signal conversion factor and a calorific value factor for the basic gas mixture so that the obtained product indicates gas consumption in an energy unit. With a further correction factor, the actual heat value of a supplied gas mixture can be taken into account at least approximately in the energy calibration. As actual heat value, a measured heat value which is averaged over a specific time span can be used. It is disadvantageous that an external unit is required to determine the heat value. 
   EP 1 227 305, a method and a gas meter for determining a gas consumption from a corrected mass flow signal or energy supply signal are disclosed. On the static gas, diffusivity and therefrom a gas-specific correction value f* for the mass flow or energy supply is determined thereby from a measured heating time. 
   In EP 0 373 965, a method and a device for determining a gas or energy consumption from a corrected mass flow signal are disclosed. During the signal correction, the heat conductivity, specific heat capacity and density of the gas are taken into account. The corrected mass flow signal and hence gas or energy consumption signal is independent of the type of gas and in particular is identical for air, argon, helium, carbon dioxide, methane and propane. It is disadvantageous that a mass flow signal standardised in such a way is not sensitive to the heat value of a gas or gas mixture since combustible gases with different heat values (e.g. methane or propane) produce the same mass flow signals and even the same signals as non-combustible gases (e.g. helium, argon, carbon dioxide or air). 
   In the U.S. Pat. No. 5,311,447, a method and a device for combustion-less determination of the specific heat value of natural gas are disclosed. For this purpose, specific heat value, density or proportion of inert gases are determined by empirical formulae from measured values of viscosity, heat conductivity, heat capacity, optical absorption, etc. The large measuring and computing complexity is disadvantageous in quantitative measurement of a plurality of independent gas type-dependent values and, in the case of combination thereof, with a volume flow measurement in a gas meter in order to determine a consumed quantity of energy. 
   In WO 01/18500, an improved mass flow measurement with two thermal CMOS anemometers is disclosed. On the static gas, measurements are made of heat conductivity in the case of a constant heat output and, in the case of a pulsed heat output, of heat capacity, the gas is identified and, from the specific heat value thereof together with the mass flow measurement, the total calorific value of the gas is determined. The relatively large complexity when determining the consumed quantity of energy from separate values of mass flow and specific heat value is in turn disadvantageous. In addition, the specific heat value for a sufficiently accurate determination of the energy supply must be measured continuously and with great accuracy. 
   In the article by D. Hoburg and P. Ulbig, “Statutory Metering and Calorific Value Reconstruction Systems”, Gas ● natural gas 143 (2002) No. 1, calorific value reconstruction systems for gas networks with different supply calorific values are disclosed. By simulation of the natural gas flows in the mains system, with the assistance of measuring data such as temperature and pressure, the gas constitution at any points in the gas network can be calculated. In particular the delivery calorific value at the delivery point to the customer can be calculated dynamically from the supply calorific values, supply through-flows, delivery through-flows and further auxiliary values such as network pressures. Normal gas constitution data, which must be detected by measurement technology at the supply points, are calorific value, standard density, CO 2  content and H 2  content. It is also disadvantageous that the geometry and topology of the network, in particular pipe roughnesses, are mostly inadequately known and the simulation calculation becomes altogether inaccurate. Also the result of the simulation calculation depends greatly upon the chosen pipe flow model and upon the computer power which is available. 
   SUMMARY OF INVENTION 
   the present invention relates to a method and a device for determining a gas energy supply with improved accuracy. 
   The invention resides in a first aspect in a method for measuring a gas supply, in particular in the private, public or industrial sector, by means of a gas meter which is disposed at a gas supply location of a gas supply network, a measuring signal V s , V ns , M s , E s  for a quantity consumption and/or energy consumption of the gas being determined by the gas meter by means of a through-flow sensor, a sensor error factor f i  (or f i ′, f i ″, f i ′″) of the gas meter being known in order to detect deviations between the consumption measured by the gas meter and the actual consumption, a consumption profile l i  (also l i ′, L i ) for the gas consumption, which profile is characteristic of the gas supply location, being known, the sensor error factor f i  and the consumption profile l i  for an accounting period being definable as a function of a common variable t or T and a consumption-weighted correction factor F relative to the accounting period being determined by averaging the sensor error factor f l  weighted with the consumption profile l i  and, with the correction factor F, the measuring signal V s , V ns , M s , E s  being converted into an output value V n , M, E. The conversion can be implemented in the gas meter or outwith it, e.g. at the gas network operator. The sensor error factor f i  takes into account inherent, typically gas type-dependent measuring errors of the gas meter or through-flow sensor. The consumption profile l i  is intended to reproduce the consumption behaviour of the gas energy subscriber as realistically as possible. It can be given for through-flow rates in any units, e.g. volume flow, mass flow or gas energy flow. The correction factor F is normally calculated by multiplication or in a similarly operating manner by the measuring signals. The method and gas meter according to the invention has the substantial advantage that variations in the gas composition are weighted with the customer-specific consumption behaviour and are used only in such a customer-specific form for correction of the measuring signal V s , V ns , M s , E s . As a result, the accuracy of a gas volume, gas mass or gas energy measurement is significantly increased. 
   In one embodiment, the measuring signal is an operating volume signal V s , standard volume signal V ns , gas mass signal M s  or energy signal E s  measured by the gas meter and/or the output value is a supplied standard volume V n , a supplied gas mass M or a supplied gas energy E. 
   In another embodiment, the averaging comprises summation and/or integration over the common variable of products which contain the sensor error factor and the consumption profile, and/or the averaging is implemented taking into account a heat value profile H i  (or H i ′) relative to the common variable. In particular, the averaging includes a suitable standardisation function. 
   The embodiment according to claim  4 a has the advantage that a measuring signal can be added up in the gas meter over for example half a year or an entire year, read by the gas man or transmitted and corrected only subsequently with respect to variations in gas composition and in particular in heat value. The correction factor F can be determined by an independently implemented averaging, in particular a priori, simultaneously or a posteriori for measuring signal detection. Hence, in the case of non-registering gas meters, the time-averaged measuring signal can be corrected in a customer-specific manner with little complexity without heat value variations and/or gas load profiles requiring to be detected locally or transmitted to the gas supply location. The subsequent measuring signal correction can be implemented in principle also in the gas meter itself. 
   The embodiment according to claim  4 b has the advantage that a measuring signal can be detected during registering operation and converted or corrected immediately or with a slight time delay with a currently determined correction factor F. In the current correction factor F, for example measured or predicted values of the sensor error factor f i , of the consumption profile l i  and if necessary of the heat value H i  can be taken into account. As a result, a registering gas meter can be produced with the highest measuring accuracy. The current measuring signal correction can be implemented in the gas meter or outwith the gas meter. 
   The embodiment according to claim  5  has the advantage that, in the case of a known gas composition, the sensor error factor f i  and, if required, the heat value H i  can be determined immediately. 
   The embodiment according to claim  6  has the advantage that the gas composition is already known to the operator or can be determined easily by the operator and/or can be calculated by means of known simulation models for gas flows in the network. 
   The embodiment according to claim  7  has the advantage that the sensor error factor f i , the consumption profile l i  and if necessary the heat value H i  can be represented as a function of time or temperature and averaged together. 
   The embodiments according to claim  8  and  9  have the advantage that the local gas subscriber can choose that gas consumption or load profile l i  which can be determined easily and can be updated simply if necessary, which demands little computing complexity and in particular memory requirement and/or which has the greatest prediction force for the gas consumption to be expected. 
   The embodiments according to claim  10 – 12  relate to concrete computer specifications for exact calculation of the correction factor F when using the gas meter as volume, gas mass or gas energy measuring device. 
   The embodiments according to claim  13 – 15  relate to calibration of the gas meter as energy measuring device, in particular an inherent dependency of the thermal through-flow sensor signal upon the heat value H i  being able to be taken into account in order to improve the accuracy of the gas energy measurement. 
   The invention resides in a second aspect in a gas meter for measuring a gas supply, in particular in the private, public or industrial sector, the gas meter being disposed at a gas supply location of a gas supply network and having a through-flow sensor and a measuring and evaluating unit for determining a measuring signal V s , V ns , M s , E s  for a quantity and/or energy consumption of the gas, furthermore computing means for determining and/or storing a typically gas type-dependent sensor error factor f i  (also f i ′, f i ″, f i ′″) of the gas meter and a consumption profile l i  (also l i ′, L i ) which is characteristic of the gas supply location and also for calculating a correction factor F by weighted averaging of the sensor error factor f i  with the consumption profile l i  being present and furthermore computing means for converting the measuring signal V s , V ns , M s , E s  by means of the correction factor F into an output value V n , M, E of the gas meter being present. Preferably, a data memory for storing the sensor error factor f i  and the consumption profile l i  as a function of a common time variable and/or temperature variable are present and/or the computing means and/or the data memory are disposed outwith the gas meter or in the gas meter. 
   The embodiments according to claims  18 – 20  enable a particularly simple construction and operation of the gas meter as energy measuring device. 
   Further embodiments, advantages and applications of the invention are revealed in the dependent claims and also in the description and Figures which now follow. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  shows, in cross section, a pipe with a through-flow, having a thermal gas meter with means for improved measuring signal correction according to an exemplary embodiment of the present invention; 
       FIG. 2  shows a gas distribution network; 
       FIG. 3  shows a load profile of a gas consumer at a gas supply location; and 
       FIG. 4  shows measurement curves for natural gas for demonstrating a partially correlated behavior of monthly average values of sensor signals of the thermal gas meter with heat values of natural gas. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a gas meter  1  comprising a thermal through-flow or mass flow sensor  1   a  which comprises a sensor element  1   a,  which is disposed in a flow channel or pipe  2 , and a measuring and evaluating unit  7 . In the pipe  2  flows a gas  3   b  with a flow and velocity profile  4 . The sensor element  1   a  is subjected to a flow velocity v to be measured. The through-flow sensor  1   a  comprises a heating element  6 , a first temperature sensor  5   a  upstream and a second temperature sensor  5   b  downstream. From temperature signals T 1 , T 2 of the temperature sensors  5   a,    5   b,  a mass flow or standard volume flow signal S can be determined in a known manner. The principal mode of operation is based on the fact that a temperature distribution through the flow  4 , produced by the heating element  6 , becomes asymmetric and a temperature difference T 1 −T 2  at the temperature sensors  5   a,    5   b  is used as a measure of the flow velocity v or the mass flow dm/dT. The mass flow signal S is to a good approximation proportional to the temperature difference T 1 −T 2 . In addition in the present case, energy signals E s  are determined and output, by means of a first basic heat value factor H CH  relative to a basic gas mixture, by the measuring means  7  from the mass flow signal S or in general sensor signal S of the through-flow sensor  1   a.  In this way, a calibration of the gas meter  1  as energy measuring device is achieved. The calibration as energy measuring device is disclosed in WO 01/96819 A1, the content of which is herewith introduced in the present disclosure in its entirety by reference. Likewise, the three articles cited therein relating to the CMOS anemometer by J. Robadey and F. Mayer et al. may be introduced here by reference. The CMOS anemometer described there is particularly suitable as sensor element  1   a  of the through-flow sensor. 
   According to the invention, a typically gas type-dependent sensor error factor f i , f i ′, f i ″, f i ′″ and a customer-specific consumption profile l 1 , l i ′, L i  is determined or detected by the gas meter  1 , a correction factor F is calculated therefrom and, with this, a measuring signal V s , V ns , M s , E s  of the gas meter  1 , in particular an energy signal E s , is converted into an output value V n , M, E, in particular a gas energy E, with improved calibration accuracy. The method is represented in detail in the course of the description and in various embodiments. 
   Instead of the through-flow sensor  1   a  with two temperature sensors  5   a,    5   b  and in particular instead of the CMOS anemometer  1   a,  also a thermal through-flow sensor can be used in general for the operability of the gas meter  1  as volume, mass or energy meter  1 , in which through-flow sensor the gas  3   b  is guided via a sensor element which has a heating means for temperature change and a sensor means for determining its temperature, the flow-dependent temperature change in turn being a measure of the through-flow or mass flow. Alternatively, the thermal through-flow sensor  1   a  can also be operated with only one temperature sensor  5   a  which is disposed upstream. The method according to the invention can also be implemented with any non-thermal gas meter  1  which, upon a through-flow, e.g. a mass flow, delivers calibrated signals. In general, the mass flow dm/dt can be indicated in mass or, in the case of a constant gas type, in standard volume units, e.g. in kg/min or can be determined according to dm/dt=ρ*dV/dT by means of the density p from a volume flow dV/dT. 
     FIG. 2  shows a diagram of a gas supply network  11  with gas supply locations  12 , consumers  13  and measuring points  15 , in particular for through-flow measurement and if necessary pressure or temperature measurement. The distribution network  11  is controlled and monitored by a central office or by an operator  10 . The gas supply location, at which a gas meter  1  according to the invention is installed, is designated for example with  14 . A supplied gas composition  3   a  or a gas composition  3   b  present at the gas supply location  14  can be determined by an operator  10  of the gas supply network  11 , for example from empirical values, measuring values, prognosis values or values of the gas quality derived therefrom. The gas composition  3   b  at the gas supply location  14  can also be calculated at least approximately from the supplied gas quality by means of simulation calculation for gas flows in the gas supply network  11 . Methods for this purpose can be deduced for example from the initially mentioned article by D. Hoburg and P. Ulbig, which is introduced herewith in its entirety by reference. 
   Preferably, the gas meter  1  is operated in the conventional manner in a non-registering manner, is read now and again and subsequently the integral measuring signal V s , V ns , M s , E s  is converted into the more precise output value V n , M, E. The conversion can be implemented subsequently in the gas meter  1  or preferably outwith it, for example at the network operator  10 . 
   The method can also be applied to a registering gas meter  1 . For this purpose, a gas meter  1  comprises a receiving unit  9  for receiving heat value data of a gas composition  3   b  present at the gas supply location  14  from an external unit  10 , in particular an operator  10  of the entire gas network  11  or of a partial network. The operator  10  can ascertain measuring data by himself or through external locations and use analysis means to determine the gas composition  3   a.  He can deliver to the local gas meter  1  raw data or prepared data, in particular a specific heat value profile H i , H i ′, for the local gas composition  3   b  or the one present in the relevant sub-network. Calculation and data transmission to the gas meter  1  can be repeated at prescribable time intervals. The reliability of the energy measurement is significantly increased since, using global and local data, an improved heat value correction can be implemented. The global data relate to the gas supply and gas distribution in the network. They are present at the operator  10  and can be used in a manner known per se to determine a local gas composition  3   b  relating to the gas supply location  14 . Data relating to the local gas consumption behaviour l i , l i ′, L i  of the customer, which can be detected by the gas meter  1 , can be collected directly in situ or be determined in another manner. By combining these data, the gas energy supply E from the energy measuring device  1  is determined with significantly improved accuracy. This combination of the data and the conversion of the measuring signal V s , V ns , M s , E s  to the more precise output value V n , M, E can be implemented in the gas meter  1  or outwith the gas meter  1 , for example at the network operator  10 . Deviating from the representation in  FIG. 1 ,  9  then serves as transmission unit for transmitting the measuring signals V s , V ns , M s , E s  to the central office  10 , where the computing units  7   a,    7   b  and/or the data memory  7   d  are preferably present. 
     FIG. 3  shows a load profile of the gas consumer at the supply location  14 . The consumption profile l i , l i ′, L i  can be a gas quantity load profile l (T) relative to a standard volume V n , a gas mass load profile l i ′ (T) relative to a gas mass M or a gas energy load profile L i  (T) relative to a gas energy E. By way of example, a gas consumption profile l (t) is plotted e.g. in energy units per day (kWh/d) against a temperature T in ° C. The gas consumption characteristic can be approximated for example by a function l (T)=(A+e B*T+C ) −1 +D, wherein A, B, C and D are determinable, consumer-specific parameters. Other functions or approximation formulae l (T) for approximation or prediction of the gas supply behaviour are also possible, similarly the tabular storage of support point values l i  with discreet temperature values T i  with i=integer index. The consumption profile l i , l i ′, L i  can be determined globally for a section of the gas supply network  11  comprising the gas supply location  14  or locally for the gas supply location  14 . The functional correlation l (T) or support point values l i  (T i ) can be obtained from empirical values, measuring values, prognosis values or values derived therefrom for a gas consumption to be expected at the gas supply location  14 . The temperature variable T can describe an outside temperature or a temperature average value at the gas supply location  14 . Alternatively, the load profile l i , l i ′, L i  can be defined for a time variable, in particular dependent upon time of day, weekday, month or course of a year. 
   The sensor error factor f i , f i ′, f i ″, f i ′″ and in particular a heat value or heat value profile H i , H i ′ can be determined from the gas composition  3   a,    3   b,  for example by means of calibration tables. Advantageously, the gas composition  3   a,    3   b  and the consumption profile l i , l i ′, L i  are known as a function of the common variables t, T. The sensor error factor f i , f i ′, f i ″, f i ′″ and if necessary the heat value profile H i , H i ′ can also be given themselves directly as a function of the common variables t, T and thus can be correlated with the consumption profile l i , l i ′, L i . 
   In the following, embodiments for computing specifications are indicated for using the gas meter  1  as an improved volume, mass or energy measuring device. The calculation is implemented for example with support values or average values in a time interval indexed with i; instead of adding support point values, integrals of function values can also be formed over the common variable, e.g. time. There applies:
 
 V   n   =V   s   ·K   (E1)
 
 K= 1/Σ i ( l   i   ·f   i )  (E2)
 
with output value V n =supplied standard volume (=standard volume added up over a specific time=integral of the standard volume through-flow rate for current gas composition  3   a ) and measuring signal V s =operating volume added up in the period of time, K=correction factor F, l i =V ni /V n =gas quantity load profile relative to standard volume (standardisation e.g.: Σ i V n,i =V n , i.e. Σ i l i =1), f i =V si /V ni =sensor error factor for operating volume measuring errors, V si =operating volume signal (indicated by gas meter  1 , pressure- and temperature-dependent) and V ni =standard volume (actually supplied) in the time interval i. There is in fact
 
 V   si   =V   ni   ·f   i   =l   i   ·f   i   ·V   n   (E3)
 
 V   s =Σ i   V   si   =V   n ·Σ i ( l   i   ·f   i )  (E4)
 
   If a standard volume signal V ns  is detected by the gas meter  1  as measuring signal (=added-up standard volume measured actually over a specific time by the gas meter  1 =integral of the measured through-flow rate for current gas composition  3   a ) and is added up in the accounting period, then there applies
 
 V   n   =V   ns   ·K′   (E10)
 
 K′= 1/Σ i ( l   i   ·f   i ′)  (E20)
 
with K′=correction factor F, f i ′=V nsi /V ni =sensor error factor for standard volume measuring errors, V nsi =standard volume signal and V ni =standard volume in the time interval i. There is in fact
 
 V   nsi   =V   ni   ·f   i   ′=l   i   ·f   i   ′·V   n   (E30)
 
 V   ns =Σ i   V   nsi   =V   n ·Σ i ( l   i   ·f   i ′)  (E40)
 
   If a gas mass signal M s  is detected by the gas meter  1  as measuring signal and added up in the accounting period and a corrected gas mass M is calculated as output value, then there applies
 
 M=M   s   ·K″   (E11)
 
 K″= 1/Σ i ( l   i   ′·f   i ″)  (E21)
 
with K″=correction factor F, l i ′=M i /M=gas quantity load profile relative to gas mass, f i ″=M si /M i =sensor error factor for gas mass measuring errors, M si =gas mass signal and M i =gas mass in the time interval i. There is in fact
 
 M   si   =M   i   ·f   i   ″=l   i   ′·f   i   ″·M   (E31)
 
 M   s =Σ i   =M   si   M·Σ   i ( l   i   ′·f   i ″)  (E41)
 
   When using the gas meter  1  as gas energy measuring device  1 , several formulations are also possible, a few of which are indicated subsequently by way of example. If an operating volume signal V s  is detected by the gas meter as measuring signal and added up in the accounting period and a corrected supplied gas energy E is calculated as output value, then there applies
 
 E=V   s   ·H   gew,s   (E12)
 
 H   gew,s =Σ i ( H   i   ·l   i )/Σ i ( l   i   ·f   i ) or   (E22a)
 
 H   gew,s =1/Σ i ( L   i   ·f   i   /H   i )  (E22b)
 
with H gew,s =weighted specific heat value per standard volume=correction factor F, H i =heat value profile per standard volume, l i =V ni /V n =gas quantity load profile relative to standard volume V n  or L i =E i /E=gas energy load profile relative to gas energy E, f i =V si /V ni =sensor error factor for operating volume measuring errors, V si =operating volume signal, V ni =standard volume and E i =gas energy in the time interval i. With (E4) there is of course on the one hand
 
 V   ni   =V   n   ·l   i   =V   s   ·l   i /Σ i ( l   i   ·f   i )  (E32a)
 
 E   i   =H   i   ·V   ni   (E42a)
 
 E=Σ   i   E   i   =V   s Σ i ( H   i   ·l   i )/Σ i ( l   i   ·f   i )  (E52a)
 
and on the other hand
 
 E   i   =E·L   i   =H   i   V   ni   (E32b)
 
 V   si   =V   ni   ·f   i   =E·L   i   ·f   i   /H   i   (E42b)
 
 V   s =Σ i   V   si   =E·Σ   i ( L   i   ·f   i   /H   i )  (E52b)
 
   If a standard volume signal V ns  is detected by the gas meter  1  as measuring signal and added up in the accounting period, then there applies
 
 E=V   ns   ·H   gew,ns   (E13)
 
 H   gew,ns =Σ i ( H   i   ·l   i )/Σ i ( l   i   ·f   i ′) or   (E23a)
 
 H   gew,ns =1/Σ i ( L   i   ·f   i   ′/H   i )  (E23b)
 
with H gew,ns =weighted specific heat value per standard volume=correction factor F, H i =heat value profile per standard volume, l i =V ni /V n =gas quantity load profile or L i =E i /E=gas energy load profile, f i ′=V nsi /V ni =sensor error factor for standard volume measuring errors, V nsi =standard volume signal and V ni =standard volume in the time interval i. With (E40) there is of course on the one hand
 
 V   ns   =V   n ·Σ i ( l   i   ·f   i ′)  (E40)
 
 V   ni   =V   n   ·l   i   =V   ns   ·l   i /Σ( l   i   ·f   i ′)  (E33a)
 
 E   i   =H   i   ·V   ni   (E43a)
 
 E=Σ   i   E   i=V   ns Σ i ( H   i   ·l   i )/Σ i ( l   i   ·f   i ′)  (E53a)
 
   On the other hand there applies
 
 E   i   =E·L   i   =H   i   ·V   ni   (E33b)
 
 V   nsi   =V   ni   ·f   i   ′=E·L   i   ·f   i   ′/H   i   (E43b)
 
 V   ns =Σ i   V   nsi   =EΣ   i ( L   i   ·f   i   ′/H   i )  (E53b)
 
   If a gas mass signal M s  is detected by the gas meter  1  as measuring signal and added up in the accounting period, then there applies
 
 E=M   s   ·H   gew,M   (E14)
 
 H   gew,M =Σ( H   i   ′·l   i ′)/Σ i ( l   i   ′·f   i ″) or   (E24a)
 
 H   gew,M =1/Σ i ( L   i   ·f   i   ″/H   i ′)  (E24b)
 
with H gew,M =weighted specific heat value per mass=correction factor F, H i ′=heat value profile per mass, l i ′=M i /M=gas mass load profile relative to gas mass M, f i ″=M si /M i =sensor error factor for gas mass measuring errors, M si =gas mass signal and M i =gas mass in the time interval i. With (E41) there applies of course on the one hand
 
 M   s =Σ i   M   si   =M·Σ   i ( l   i   ′·f   i ″)  (E41)
 
 M   i   =M·l   i   ′=M   s   ·l   i ′/Σ i ( l   i   ′·f   i ″)  (E34a)
 
 E   i   =H   i   ′·M   i   (E44a)
 
 E=Σ   i   E   i   =M   s Σ i ( H   i   ′·l   i ′)/Σ i ( l   i   ′·f   i ″)  (E54a)
 
   On the other hand there applies
 
 E   i   =E·L   i   =H   i   ′·M   i   (E34b)
 
 M   si   =M   i·f   i   ″=E·L   i   ·f   i   ″/H   i ′  (E44b)
 
 M   s =Σ i   M   si   =E·Σ   i ( L   i   ·f   i″   /H   i ′)  (E54b)
 
   If a gas energy signal E s  is detected by the gas meter  1  as measuring signal and added up in the accounting period, then there applies
 
 E=E   s   ·h   gew   (E15)
 
 h   gew =Σ i ( H   i   ·l   i ′)/Σ i ( H   i   ·l   i   ·f   i ′″) or   (E25a)
 
 h   gew =1/Σ i ( L   i   ·f   i ′″)  (E25b)
 
with h gew =weighted heat value correction factor=correction factor F, H i =E i /V ni =heat value profile per standard volume, l i =V ni /V n =gas quantity load profile or L i =E i /E=gas energy load profile, f i ′″=E si /E i =sensor error factor for gas energy measuring errors, E si =gas energy signal and E i =gas energy in the time interval i. There applies in fact on the one hand
 
 E   i   =H   i   ·V   ni   =V   n   ·H   i   ·l   i   (E35a)
 
 E   si   =E   i   ·f   i   ′″=V   n   ·H   i   ·l   i   ·f   i ′″  (E45a)
 
 E   s =Σ i   E   si   =V   n Σ i ( H   i   ·l   i   ·f   i ′″)  (E55a)
 
 E=Σ   i   E   i   =V   n Σ i ( H   i   ·l   i )  (E65a)
 
 E=E   s ·Σ i ( H   i   ·l   i )/Σ i ( H   i   ·l   i   ·f   i ′″)  (E66a)
 
   On the other hand, there applies
 
 E   i   =E·L   i   (E35b)
 
 E   si   =E   i   ·f   i   ′″=E·L   i   ·f   i ′″)  (E45b)
 
 E   s =Σ i   E   si   =EΣ   i ( L   i   ·f   i ′″)  (E55b)
 
   For energy accounting, the gas energy E should be multiplied by the price per energy unit. This price can if necessary also be time-dependent, which in the case of the heat value weighting, in particular in the heat value correction factor h gew , can also be taken into account. 
   In the above-mentioned examples, the sensor error factor f i , f i ′, f i ″, f i ′″ is chosen without dimension. Further embodiments for determining correction factors F can be obtained as a result of the fact that other combinations of measuring signal and output value are chosen and the auxiliary values sensor error factor, consumption profile and if necessary heat value profile are suitably defined in order to combine together measuring signal and output value or their temporally averaged values. By way of example, dimension-associated sensor error factors can be introduced, e.g. f i   v =V si /M i , in order, with a given dimensionless sensor error factor, to convert load profile, heat value profile and/or measuring signal, instead of to an output value, e.g. standard volume, to a different output value, e.g. gas mass. In addition, a conversion could be performed of an energy signal E s  to a standard volume or to a gas mass M. Such and similar embodiments may herewith be disclosed jointly in an explicit manner. 
   The through-flow sensor  1   a  is preferably a thermal through-flow sensor  1   a,  with which a sensor signal S kal  calibrated to a through-flow rate is determined. In order to calibrate the gas meter  1  as energy measuring device  1 , the calibrated sensor signal S kal  is calibrated using a basic heat value factor H CH  for a basic gas mixture CH into the gas energy signal E s . 
   According to WO 01/96819 A1, there is effected in the thermal through-flow sensor  1   a,  in particular in the CMOS anemometer through-flow sensor  1   a,  an inherent automatic heat value tracking in the case of deviations of the current gas mixture  3   b  from the basic gas mixture CH. Since the inherent heat value tracking is incomplete, now, starting from the first energy calibration for the basic gas mixture CH, a second improved energy calibration is implemented according to the invention by means of the weighted heat value correction factor F=h gew . 
   For the mentioned gas energy measuring device  1  with thermal through-flow sensor  1   a,  the underlying measuring method is now described in more detail. According to WO 01/96819 A1, a sensor signal S N2  (previously S) for a calibration gas, typically nitrogen N 2  or air, is determined and calibrated to an (uncorrected) mass flow signal S m  (previously S(d(V N2,n )/dt), d(V N2,n )/dt=standard volume flow for calibration gas). The calibration can be expressed by a sensor calibration curve F(S N2 ) for the calibration gas under normal conditions, S m  being proportional to F(S N2 ) or simply S m =F(S N2 ). The mass flow signal S m  still depends upon the type of gas. Hence, deviations of the mass flow signal S m  from an exact ideal value for a basic gas mixture, typically natural gas or in general a hydrogen mixture CH, are corrected by a signal conversion factor or sensor signal correction factor f N2-CH . Hence there applies S M =S m ·f N2-CH  with S M =corrected mass flow signal. In the sense of this disclosure, S M  is equal to or proportional to the previously mentioned calibrated sensor signal S kal  of the through-flow sensor  1   a.  Likewise, the gas standard volumes V ns,i  and V ns  in the case of sufficiently constant gas quality, are equal to or proportional to the calibrated sensor signals S kal  or average values of S kal  in the associated time interval i. The calibrated sensor signal S kal  is therefore a measure of and in particular proportional to a through-flow rate of the gas composition  3   b  to be measured. Therefore S kal =S m ·f N2-CH  can be written, a possibly necessary proportionality factor being taken into account in the sensor calibration curve F(S N2 ). Finally, an energy signal E s  is determined by multiplication of the calibrated sensor signal S kal  by a heat value H CH  (calorimetric value per unit of the through-flow value, i.e. per standard volume or per mass) of the basic gas mixture: E S =∫S kal ·H CH ·dt=f N2-CH ·H CH ·∫F(S N2 )·dt or E s =S kal ·H CH  with S kal =averaged calibrated sensor signal. 
   According to WO 01/96819 A1 or EP 1 227 305, introduced herewith in their entirety by reference, also suitable time average values can be used for the mentioned values S N2 , F(S N2 ), f N2-CH  and H CH  and values derivable therefrom. 
     FIG. 4  shows how heat value variations up to a fraction are detected inherently from the sensor signals S kal  of the through-flow sensor  1   a.  This characteristic is known per se from WO 01/96819 A1 and can be stored quantitatively in the gas meter  1  for example as sensor error factor f i ′″=E si /E i . The sensor error factor f i ′″ is therefore chosen to be proportional to the deviations between the inherently detected and the actual heat value variations of the gas composition  3   b  at the gas supply location  14  or as an average of these deviations. These deviations, i.e. the inherent heat value dependency of the energy signals E s  relative to a basic gas mixture CH, are corrected in that the sensor error factor f′″ in the correction factor F according to the invention is taken into account and the energy signals E s  are calibrated by means of the correction factor F subsequently and/or offline to improved or corrected or actual gas energy output values E. 
   The invention also has a gas meter  1  for implementing the above-described method as subject. According to  FIG. 1 and 2 , the gas meter  1  is disposed at a gas supply location  14  of a gas supply network  11  and has a through-flow sensor  1   a  and a measuring and evaluating unit  7  for determining a measuring signal V s , V ns , M s , E s  for a quantity and/or energy consumption of the gas  3   a,  the measuring and evaluating unit  7  having computing means  7   a  for determining and/or storing a sensor error factor f i , f i ′, f i ″, f i ′″ of the gas meter  1  and a consumption profile l i , l i ′, L i  characteristic of the gas supply location  14  and also for calculating a correction factor F by weighted averaging of the sensor error factor f i , f i ′, f i ″, f i ′″ with the consumption profile l i , l i ′, L i , and the measuring and evaluating unit  7  has furthermore computing means  7   b  for converting the measuring signal V s , V ns , M s , E s  by means of the correction factor F into an output value V n , M, E of the gas meter  1 . Preferably, the measuring and evaluating unit  7  comprises a data memory  7   d  for storing the sensor error factor f i , f i ′, f i ″, f i ′″ and the consumption profile l i , l i ′, L i  as a function of a common time variable and/or temperature variable T. 
   Advantageously, the through-flow sensor  1   a  is a thermal through-flow sensor  1   a,  in particular a CMOS anemometer  1   a,  with a heating wire  6  and temperature sensors  5   a,    5   b  disposed upstream and downstream. The measuring and evaluating unit  7  has in particular means for calibration of the gas supply in energy units kW/h. 
   Furthermore, the measuring and evaluating unit  7  can comprise computing means  7   c  for determining a calibrated sensor signal S kal  by means of re-evaluation of a calibration gas to a basic gas mixture CH and for determining a gas energy signal E s  by means of multiplication of the calibrated sensor signal S kal  by a basic heat value factor H CH . In particular, computing means  7   a  for determining and/or storing a sensor error factor f i ′″ for gas energy measurement is present for detection and correction of an inherent dependency of the calibrated sensor signal S kal  of the through-flow sensor  1   a  upon heat value variations. The computing unit  7   a,    7   b,    7   c  and/or the data memory  7   d  can also be disposed outwith the gas meter  1 . 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               Reference number list 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               1 
               Gas meter 
             
             
               1a 
               Thermal mass flow sensor, CMOS sensor 
             
             
               1b 
               Membrane 
             
             
               2 
               Flow channel, pipe 
             
             
               3a 
               Gas composition in the gas network; natural gas 
             
             
               3b 
               Gas composition at the supply location; natural gas 
             
             
               4 
               Flow profile 
             
             
               5a,5b 
               First, second temperature sensor, thermoelements 
             
             
               6 
               Heating element, heating wire 
             
             
               7 
               Measuring and evaluating unit 
             
             
               7a,7b,7c 
               Computing means 
             
             
               7d 
               Data memory 
             
             
               8 
               Signal output, display 
             
             
               9 
               Receiving unit, transmitting unit (optional) 
             
             
               10 
               External unit, operator, central office 
             
             
               11 
               Gas supply network 
             
             
               12 
               Gas supply 
             
             
               13 
               Consumer 
             
             
               14 
               Gas supply location 
             
             
               15 
               Through-flow measurement, measuring point of the 
             
             
                 
               operator 
             
             
               CH 
               Natural gas, basic gas mixture 
             
             
               F(S N2 ) 
               Sensor calibration curve 
             
             
               f N2-CH   
               Signal conversion factor 
             
             
               f i ,f i ′,f i ″,f i ′″ 
               Sensor error factor 
             
             
               F 
               Correction factor 
             
             
               H CH   
               Basic heat value factor for the basic gas mixture 
             
             
               H i , H i ′ 
               Heat value, heat value profile of the gas composition 
             
             
               H gew,s , H gew,ns   
               Weighted heat value per standard volume 
             
             
               H gew,M   
               Weighted heat value per gas mass 
             
             
               h gew   
               Weighted heat value correction factor 
             
             
               K,K′,K″ 
               Volume correction factor, mass correction factor 
             
             
               l i ,l i ′,L i ″ 
               Gas consumption profile, load profile 
             
             
               S 
               Sensor signal 
             
             
               S m   
               Uncorrected mass flow or sensor signal 
             
             
               S M   
               Corrected mass flow signal for the basis gas mixture 
             
             
               S N2   
               Calibration gas sensor signal 
             
             
               S kal   
               Calibrated sensor signal 
             
             
               t 
               Time variable 
             
             
               T,T 1 ,T 2   
               Temperatures 
             
             
               v 
               Flow velocity 
             
             
               V s ,V ns ,M s ,E s   
               Measuring signal 
             
             
               V n ,M,E 
               Output value 
             
             
               i 
               Index for time interval 
             
             
               s 
               Index for measuring signal