JP2019032282A - Driving method, driving device, and vortex flowmeter for thermo-sensitive element - Google Patents

Abstract

To provide a driving method, a driving device and a vortex flowmeter of a thermo-sensitive element for automatically maintaining sensitivity of a sensor even when the temperature changes.SOLUTION: There is provided a driving method of a thermo-sensitive element for compensating an output change caused by temperature characteristics of the thermo-sensitive element whose resistance value changes due to a change in the temperature, which includes: a resistance value calculation step 40 for calculating a resistance value of the thermo-sensitive element; a temperature compensation calculation step 41 for obtaining a drive voltage or drive currents of the thermo-sensitive element for making constant the output change with respect to a change in the temperature of the thermo-sensitive element even when an ambient temperature or the temperature of a measured fluid changes from the calculated resistance value; and a drive voltage or drive current control step 42 for outputting the obtained drive voltage or drive currents to the thermo-sensitive element.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a temperature sensing element driving method, a driving apparatus, and a vortex flowmeter, and more specifically, a temperature sensing element that compensates for an output change due to a temperature characteristic of a temperature sensing element whose resistance value changes due to a temperature change. The present invention relates to a driving method, a driving device, and a vortex flowmeter.

  A vortex flowmeter is composed of a vortex generator (also called a bluff body) that generates Karman vortices, a sensor that detects Karman vortices (for example, a temperature sensing element), and a transducer that processes the signals detected by the sensors. Is done. The vortex generator is formed in a triangular prism shape, for example, and is placed at right angles to the fluid flow in the measurement tube. The sensor (temperature sensing element) can detect and detect the differential pressure generated by the Karman vortex generated in the vortex generator as a change in flow velocity.

The frequency at which Karman vortices are generated (also called vortex frequency) is proportional to the flow velocity. In the converter, the flow velocity in the measurement tube is obtained from the detected vortex frequency, and the flow rate is obtained by multiplying this flow velocity by the cross-sectional area of the measurement tube.
In the converter, when detecting the eddy frequency, the signal output from the sensor is passed through a band-pass filter to remove noise. For example, Patent Document 1 discloses a technique for selecting a band pass filter to pass.

JP 2001-153698 A

  By the way, when the ambient temperature or the temperature of the fluid to be measured is low, the sensitivity of the sensor (specifically, the magnitude of the output change with respect to the temperature change) decreases. When the sensitivity of the sensor is reduced, the amplitude of the signal waveform after filtering is reduced, and an appropriate bandpass filter cannot be selected. For this reason, if this signal waveform is pulsed, noise will not be pulsed as a signal, or conversely, the signal will not be pulsed as noise, so the trigger waveform will have irregular intervals and amplitudes, and the output pulse will be mixed with noise. .

In rare cases, when the ambient temperature or the temperature of the fluid under measurement is low and noise is likely to be mixed with the output pulse, the operator must set the sensor drive voltage at the installation site of the vortex flowmeter to increase the sensitivity of the sensor. Manual adjustment is required.
However, vortex flowmeters, which are industrial instruments, are often installed in hazardous locations (explosion-proof equipment is required), making it difficult to adjust the sensor drive voltage, and during this adjustment, measurement by the sensor must be interrupted. There is a problem that must be.

  The present invention has been made in view of the above circumstances, and provides a driving method, a driving device, and a vortex flowmeter for a temperature-sensitive element for automatically maintaining the sensitivity of the sensor even when the temperature changes. The purpose is to do.

  In order to solve the above-mentioned problem, a first technical means of the present invention is a method of driving a temperature sensing element that compensates for an output change due to a temperature characteristic of a temperature sensing element whose resistance value changes due to a temperature change. A resistance value calculating step for obtaining a resistance value of the temperature sensing element, and the sense that the output change with respect to the temperature change of the temperature sensing element is constant from the obtained resistance value even if the ambient temperature or the temperature of the fluid to be measured changes. A temperature compensation calculation step for obtaining a drive voltage or drive current of the temperature element; and a drive voltage or drive current control step for outputting the obtained drive voltage or drive current to the temperature sensitive element. .

  According to a second technical means, the temperature compensation calculating step calculates a temperature of the temperature sensitive element based on the obtained resistance value, and obtains the sensitivity of the temperature sensitive element based on the obtained temperature. A sensitivity calculation step, and the sensitivity of the temperature sensing element and the driving voltage of the temperature sensing element for maintaining the sensitivity of the temperature sensing element constant before and after the temperature change even if the ambient temperature or the temperature of the fluid to be measured changes. Alternatively, based on the relationship with the drive current, a compensation coefficient calculation step for obtaining a compensation coefficient for the drive voltage or drive current of the temperature sensing element from the sensitivity obtained in the sensitivity calculation step, and the sensitivity based on the obtained compensation coefficient. And a drive voltage or drive current calculation step for obtaining a drive voltage or drive current of the temperature element.

  A third technical means is characterized in that the temperature sensitive element is a temperature sensitive element sensor.

  A fourth technical means is a temperature sensing element driving device that compensates for a change in output due to a temperature characteristic of a temperature sensing element whose resistance value varies with a temperature change, and calculates a resistance value for obtaining a resistance value of the temperature sensing element. And a temperature for obtaining a driving voltage or a driving current of the temperature sensing element from which the output change with respect to the temperature change of the temperature sensing element is constant even if the ambient temperature or the temperature of the fluid to be measured changes from the obtained resistance value It has a compensation calculation part and a drive voltage or drive current control part for outputting the obtained drive voltage or drive current to the temperature sensitive element.

  A fifth technical means is a vortex flowmeter characterized by implementing the above-described temperature sensing element driving method.

  According to the present invention, the drive voltage (drive current) that makes the output change constant with respect to the temperature change is obtained from the resistance value of the temperature sensing element and output to the temperature sensing element. Sensitivity can be maintained automatically. As a result, in order to adjust the sensitivity of the temperature sensitive element, the operator does not have to go to the installation site of the vortex flowmeter, and there is no need to interrupt the measurement by the temperature sensitive element.

It is a figure which shows the detector of the vortex flowmeter which concerns on one Embodiment of this invention. It is a figure explaining the detection principle of Karman vortex by the detector of FIG. It is a block diagram of the vortex flowmeter of FIG. It is a block diagram of the temperature compensation calculation part of FIG. It is a figure explaining the relationship between sensor temperature and the change rate of a crest value, and the relationship between sensor temperature and a sensor drive voltage. It is a figure explaining the waveform data of a present Example.

Hereinafter, preferred embodiments of a driving method, a driving device, and a vortex flowmeter of a temperature sensitive element of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a detector of a vortex flowmeter according to an embodiment of the present invention, and shows, for example, a flange-type detector 1. FIG. 2 is a diagram for explaining the principle of Karman vortex detection by the detector of FIG.

  The detector 1 has a vortex generator 3 formed in, for example, a triangular prism shape, and a cylindrical measurement tube so that the side surface of the vortex generator 3 is perpendicular to the flow of the fluid to be measured (the arrow direction in FIG. 2). 2 is installed. A sensor housing 4 is provided on the upper surface of the measurement tube 2 and is fixed to the measurement tube 2 with a fastening member such as a bolt. A terminal box 6 is installed above the sensor housing 4 via a mounting cylinder 5.

  The detector 1 is provided with a bypass flow path. As shown in FIG. 2, the bypass channel opens to the upstream side of the vortex generator 3 (bias inlet 11) and opens to the downstream side of the vortex generator 3 via the sensor housing 4 (bias outlet). 14) In the sensor housing 4, for example, needle valves 12a and 12b, a filter 13, and a pair of temperature sensing element sensors 7 are accommodated. Note that FIG. 2 shows a diagram in which the needle valves 12 a and 12 b and the filter 13 are arranged outside the sensor housing 4 in order to facilitate explanation of the detection principle.

  As will be described later with reference to FIG. 3, the pair of temperature sensitive sensor 7 constitutes two sides of the bridge circuit and is heated by a weak current from the constant current circuit. Note that the temperature sensitive element sensor refers to, for example, a thermistor, a thermocouple, a resistance temperature detector, a semiconductor temperature sensor, and the like.

  When the fluid flows in the measuring tube 2, Karman vortices proportional to the flow velocity are generated downstream of the vortex generator 3, and alternating pressure fluctuations due to Karman vortices occur on both sides of the vortex generator 3. An alternating flow rate change in synchronization with the Karman vortex occurs in the bypass flow path, and a slight temperature change occurs on the surface of the temperature-sensitive element sensor 7. As a result, the temperature-sensitive element sensor 7 detects a signal (also referred to as a vortex signal) corresponding to the fluctuating pressure generated in the vortex generator 3 and outputs it to the converter 10 described later with reference to FIG. The More specifically, since the resistance values of the pair of temperature sensing element sensors 7 change alternately, the converter 10 can detect an alternating current synchronized with the Karman vortex. Although an example of a converter separated type in which the converter is separated from the detector will be described, a converter integrated type may be used.

FIG. 3 is a configuration diagram of the vortex flowmeter.
The converter 10 includes a flow rate indicator 16, a control unit 15, a communication I / F 17, an amplifier unit 18, a filter unit 19, and the like, which are connected by a bus. The flow rate indicator 16 displays the flow rate of the fluid to be measured obtained by the converter 10.
The control unit 15 can communicate with the detector 1 and an external device via the communication I / F 17. The control unit 15 includes, for example, one or a plurality of CPUs (Central Processing Units) and the like, for example, loads various programs and data stored in the ROM into the RAM, and loads the programs in the loaded RAM. Run. Thereby, the operation of the vortex flowmeter can be controlled.

The amplifier unit 18 includes, for example, a constant current circuit 20, an amplifier 21, an output circuit 22, a sensor voltage control circuit 23, and the like. The constant current circuit 20 supplies a current to the temperature sensing element sensor 7 of the detector 1. The amplifier 21 amplifies the vortex signal output from the temperature sensitive element sensor 7. The amplified vortex signal is output to the filter unit 19.
The filter unit 19 includes a variable BPF 26 and a comparator 27. The variable BPF 26 passes the vortex signal amplified by the amplifier 21 and removes an unnecessary frequency band signal included in the vortex signal. The comparator 27 pulses the filtered waveform that has passed through the variable BPF 26. The pulsed trigger waveform is output to the output circuit 22 of the amplifier unit 18.

When a pulse output proportional to the flow rate is obtained, a frequency (also referred to as a vortex frequency) at which Karman vortices are generated can be detected. The vortex frequency is proportional to the flow velocity, and the relational expression is as follows.
f = St · V / d
f is the vortex frequency, V is the average flow velocity of the fluid, d is the width of the vortex generator, and St is the Strouhal number (constant). This Strouhal number varies depending on the Reynolds number (a numerical value that determines the flow state), but is almost constant over a wide range of Raynozzle numbers.

Therefore, it can be seen that the vortex frequency f is proportional to the average flow velocity V in the range where the Strouhal number is constant. Further, since the width d of the vortex generator is known, the average flow velocity V in the measuring tube can be obtained by detecting the vortex frequency f. Therefore, the output circuit 22 obtains the flow rate by multiplying the average flow velocity V by the cross-sectional area of the measurement tube, and outputs the flow rate to the flow rate indicator 16 or the like.
The control unit 15 includes a resistance value calculation unit 40, a temperature compensation calculation unit 41, and a drive voltage / current control unit 42.

  The resistance value calculation unit 40 obtains the resistance value of the temperature sensitive element sensor 7. Specifically, the constant current circuit 20 is provided with a current detector, a voltage detector, and an A / D converter that detect current and voltage generated in the temperature sensing element sensor 7. The resistance value of the temperature-sensitive element sensor 7 is obtained from the current value and the voltage value digitally converted by the / D converter. The calculation result of the resistance value calculation unit 40 is output to the temperature compensation calculation unit 41, and the temperature compensation calculation unit 41 compensates for the output change due to the temperature characteristic of the temperature sensing element sensor 7. In addition, although demonstrated in the example which calculates | requires the resistance value of the temperature sensing element sensor 7 from an electric current value and a voltage value, you may obtain | require the resistance value of the temperature sensing element sensor 7 with another method.

FIG. 4 is a configuration diagram of the temperature compensation calculation unit of FIG. The temperature compensation calculation unit 41 is obtained by the resistance value calculation unit 40 of FIG. 3 in order to make the magnitude of the output change with respect to the temperature change of the temperature sensing element sensor constant even if the ambient temperature or the temperature of the fluid to be measured changes. The drive voltage of the temperature sensitive sensor 7 is obtained from the sensor resistance value.
First, the temperature compensation calculation unit 41 obtains the temperature T of the temperature-sensitive element sensor from the sensor resistance value obtained by the resistance value calculation unit 40 and the resistance-temperature characteristic 41a shown in FIG.

Ｔはセンサの温度（Ｋ）、Ｒはセンサ抵抗値（Ω）、Ｂは感温素子定数（センサ固有の値である）、Ｔ₀は基準温度、Ｒ₀は基準温度のときのセンサ抵抗値であり、数１に示すように、抵抗値は、温度が高くなるに連れて指数関数的に小さくなる。 A temperature-sensitive element sensor is an element that can detect a temperature using a temperature coefficient of a semiconductor, and a resistance value changes depending on the temperature. It is known that the resistance-temperature characteristic of the temperature-sensitive element sensor is expressed by Equation 1.

T is the sensor temperature (K), R is the sensor resistance value (Ω), B is the temperature sensing element constant (a value unique to the sensor), T ₀ is the reference temperature, and R ₀ is the sensor resistance value at the reference temperature. As shown in Equation 1, the resistance value decreases exponentially as the temperature increases.

Further, Equation 1 can be transformed into Equation 2, and when this Equation 2 is arranged with respect to T, it is expressed by Equation 3. This equation 2 corresponds to the resistance-temperature characteristic 41a, and if the sensor resistance value R is obtained by the resistance value calculation unit 40 in FIG. 3, the sensor temperature T can be obtained from equation 3.

Next, the temperature compensation calculation unit 41 obtains the sensitivity of the temperature sensitive element sensor from the obtained sensor temperature T and the temperature-sensitivity characteristic 41b shown in FIG.
When a current is passed through a temperature-sensitive element sensor, it generates heat according to Joule's law (also called self-heating), but the resistance value of the sensor changes with temperature. There is a need to. The temperature difference t from the ambient temperature in the equilibrium state after sufficient time is equivalent to the temperature due to self-heating described later, and is a number depending on the current I flowing through the sensor and a predetermined proportional constant (also referred to as a heat dissipation coefficient or thermal resistance) Θ. It is represented by 4.

ｄＲ／ｄＴはセンサの温度係数であり、センサの温度により決定される。このセンサの温度係数ｄＲ／ｄＴは、数１をＴで微分して数６で表される。

よって、温度係数ｄＲ／ｄＴは負の特性を持ち、その絶対値は温度が低いほど大きくなる。 Here, it can be considered that the temperature change ΔT generated in the temperature sensing element sensor due to the generation of Karman vortex is caused by forced convection due to the temperature difference between the self-heated sensor and the fluid. The resistance change ΔR of the sensor at this time is expressed by Equation 5.

dR / dT is a temperature coefficient of the sensor and is determined by the temperature of the sensor. The temperature coefficient dR / dT of this sensor is expressed by Equation 6 by differentiating Equation 1 with T.

Therefore, the temperature coefficient dR / dT has a negative characteristic, and its absolute value increases as the temperature decreases.

Ｑは熱移動量（Ｗ）、Ａは伝搬面積（ｍ²）、Ｔｗはセンサの温度（Ｋ）、Ｔａは被測定流体の温度（Ｋ）である。
感温素子センサの周囲温度と流体の温度が等しい場合、Ｔｗ−Ｔａは自己発熱による温度ｔになり、数７はＱ＝Ａ・ｔ・ｈとなる。また、センサの熱容量Ｃとすると、Ｑ＝ＣΔＴであるので、センサの温度変化ΔＴは数８で表される。

On the other hand, considering the change in temperature of the sensor due to contact with the fluid, the heat transfer coefficient h is expressed by Equation 7.

Q is the amount of heat transfer (W), A is the propagation area (m ² ), Tw is the temperature (K) of the sensor, and Ta is the temperature (K) of the fluid to be measured.
When the ambient temperature of the temperature sensor is equal to the temperature of the fluid, Tw−Ta is a temperature t due to self-heating, and Equation 7 is Q = A · t · h. Further, assuming that the heat capacity C of the sensor is Q = CΔT, the temperature change ΔT of the sensor is expressed by Equation 8.

感温素子センサが平板であり、センサ付近の流れがセンサに対して平行な層流であると仮定すると、ヌセルト数Ｎｕ＝０．６６４Ｒｅ^1/2Ｐｒ^1/3である。Ｒｅはレイノルズ数であり（Ｒｅ＝ρｖＬ／μ、ρは流体の密度、ｖは流体の速度、μは流体の粘性係数）、Ｒｅ≦３．２×１０⁵である。また、Ｐｒはプラントル数であり、流体に固有の物性値である。 Moreover, said heat transfer coefficient h is represented by several 9 as the heat conductivity k of a fluid, and the representative length L, if the Nusselt number Nu is used.

Assuming that the temperature-sensitive element sensor is a flat plate and the flow in the vicinity of the sensor is a laminar flow parallel to the sensor, the Nusselt number Nu = 0.664 Re ^1/2 Pr ^1/3 . Re is the Reynolds number (Re = ρvL / μ, ρ is the density of the fluid, v is the velocity of the fluid, μ is the viscosity coefficient of the fluid), and Re ≦ 3.2 × 10 ⁵ . Pr is the Prandtl number and is a physical property value specific to the fluid.

この数１０のうち、Ａ、Ｃ、Ｌ、μ、Ｐｒ、ｋは定数とみなすことができるので、係数αにまとめると、数１１で表される。

そして、数５のｄＲ／ｄＴに数６を、数５のΔＴに数１１を、数１１のｔに数４をそれぞれ代入すると、数１２で表される。

Substituting Equation 9 into h in Equation 8 and substituting the above Nusselt Nu into Nu in Equation 9 yields Equation 10.

Of these formulas 10, A, C, L, μ, Pr, and k can be regarded as constants.

Then, when Expression 6 is substituted for dR / dT of Expression 5, Expression 11 is substituted for ΔT of Expression 5, and Expression 4 is substituted for t of Expression 11, the expression 12 is obtained.

In the ideal gas equation of state PV = nRτ (P is pressure, V is volume, n is the amount of substance (mole number), R is the gas constant, and τ is the temperature of the gas), the amount of substance n is w / M (w is mass) , M is the average molecular weight of the gas) and the density ρ = w / V = PM / Rτ.
If the temperature τ of the gas is regarded as constant, the density ρ is proportional to the pressure P. Therefore, when this proportionality constant (that is, M / Rτ) and the above α, Θ, and B are combined into a coefficient β, the resistance change ΔR of the temperature sensitive element sensor is expressed by Equation 13.

The resistance change ΔR of the sensor is converted from a current I flowing through the sensor into a voltage and amplified by the amplifier described with reference to FIG. When the gain G of the amplifier is used, the peak value (also referred to as amplitude value) ΔV of the vortex signal to be output is ΔV = G · I · ΔR. Therefore, when Expression 13 is substituted for ΔR, Expression 14 is obtained. .

When the temperature, pressure, etc. change under the condition of constant flow velocity, that is, when the peak value of the vortex signal changes from ΔV ₀ to ΔV (sensor resistance value, sensor current, sensor temperature, and pressure are R _0, respectively. , I ₀ , T ₀ , P ₀ to R, I, T, P), the change ratio of the peak value of the vortex signal (also referred to as the amplitude ratio, which corresponds to the sensitivity of the sensor) m is m = ΔV Since it is ₀ / ΔV, it is expressed by Equation 15. Thus, it can be seen that the change ratio of the peak value of the vortex signal can be theoretically derived from the vortex detection principle of the temperature-sensitive element sensor.

よって、数１６のＲ／Ｒ₀に数２を代入すると、数１７で表されるので、渦信号の波高値の変化比率ｍは、温度によって変化し（つまり、後述の温度による波高値の変化比率の項を有し）、センサ駆動電圧の制御によって調整できることが分かる。

More specifically, when the sensor voltage changes from V ₀ to V under a constant pressure, I = V / R, and therefore, Expression 15 is expressed by Expression 16.

Therefore, substituting Equation 2 into R / R ₀ of Equation 16 is expressed by Equation 17, so the change ratio m of the peak value of the vortex signal changes depending on the temperature (that is, the change of the peak value due to the temperature described later). It can be seen that it can be adjusted by controlling the sensor drive voltage.

The change ratio of the peak value due to this temperature is obtained. When the voltage was kept constant at T ₀ of about 20 ° C., when the peak value of the vortex signal was plotted on the vertical axis and the temperature was plotted on the horizontal axis, the equation 17 was shown as a straight line in the range of −40 ° C. to 80 ° C. . Therefore, in order to simplify the calculation, the change ratio of the peak value due to temperature is approximated by a linear expression. When Expression 17 is differentiated by T with constant voltage, Expression 18 is obtained.

したがってＴ₀付近における波高値の変化比率ｍの一次式近似（直線）は、温度（Ｔ−Ｔ₀）が最低になってもｍ＝１を維持すると想定すれば数２０で表され、これを温度による波高値の変化比率とみなす。上記数１９が温度−感度特性４１ｂに相当し、センサの温度を求めれば、数１７から感温素子センサの感度を求めることができる。

When determining the slope in the vicinity of T ₀ as T = T _0, is represented by the number 19.

Therefore, the linear approximation (straight line) of the peak value change ratio m in the vicinity of T ₀ is expressed by Equation 20 assuming that m = 1 is maintained even when the temperature (T−T ₀ ) is the lowest. It is regarded as the rate of change of the peak value due to temperature. If the above Equation 19 corresponds to the temperature-sensitivity characteristic 41b and the temperature of the sensor is obtained, the sensitivity of the temperature sensitive element sensor can be obtained from Equation 17.

  Subsequently, the temperature compensation calculation unit 41 maintains the sensitivity constant (m = 1) before and after the temperature change even if the temperature of the sensor changes, and the sensitivity-sensor voltage characteristic 41c shown in FIG. The compensation coefficient of the sensor drive voltage is obtained from the obtained sensor sensitivity. Instead of the temperature-sensitivity characteristic 41b and the sensitivity-sensor voltage characteristic 41c shown in FIG. 4A, a temperature-sensor voltage characteristic 41d may be used as shown in FIG. 4B.

そして渦信号の波高値の変化比率が一定となる条件を求めるために、ｍ＝１として、温度補償によるセンサ電圧の変化比率Ｖ／Ｖ₀について数２１を変形すると、数２２で表される。

In order to simplify the calculation, when the term of the change ratio of the crest value due to the temperature is replaced with Expression 20, Expression 17 is expressed. This is the sensitivity-sensor voltage characteristic 41c. If the sensitivity of the sensor is obtained, the sensor drive voltage can be obtained from Equation 21.

Then, in order to obtain a condition in which the change ratio of the peak value of the vortex signal is constant, when m = 1 and Equation 21 is transformed with respect to the sensor voltage change rate V / V ₀ by temperature compensation, Equation 22 is obtained.

The temperature compensation calculation unit 41 outputs the change rate V / V ₀ of the sensor voltage due to the temperature compensation to the drive voltage / current control unit 42 as the voltage compensation coefficient Vadj. The drive voltage / current control unit 42 can set the sensor drive voltage V to V ₀ × Vadj.
If this V ₀ is a sensor voltage when the ambient temperature is normal temperature (for example, 20 ° C.), when the sensor temperature T is lower than normal temperature, the drive voltage / current control unit 42 sets the sensor drive voltage V to V ₀ × Vadj is set and output to the sensor voltage control circuit 23.

The sensor voltage control circuit 23 converts the sensor drive voltage V set by the drive voltage / current control unit 42 into an analog signal using a D / A converter and outputs the analog signal to the temperature sensing element sensor 7. Thereby, the sensitivity of the sensor is kept constant.
In the above description, the sensor resistance value, the sensor temperature, and the sensor sensitivity obtained are substituted into the respective formulas to obtain the sensor temperature, the sensor sensitivity, and the sensor voltage. It is also possible to use a table, a temperature-sensitivity characteristic table, a sensitivity-sensor voltage table, or a temperature-sensor voltage table.

FIG. 5 is a diagram for explaining the relationship between the sensor temperature and the change rate of the crest value, and the relationship between the sensor temperature and the sensor drive voltage. FIG. 6 shows the waveform data of this example (time lapse of the signal voltage). FIG.
When the sensor drive voltage is not changed even though the sensor temperature is lower than about 20 ° C. (referred to as a comparative example), the change ratio of the peak value of the vortex signal is as shown by the broken line in FIG. Since it is much lower than 0.8, the sensitivity of the sensor is also greatly reduced.

On the other hand, in this embodiment, when the sensor temperature falls below about 20 ° C., the sensor drive voltage is increased to, for example, V ₀ × Vadj as shown by the one-dot chain line in FIG. As shown by the solid line in FIG. 5, the change rate of the high value is equal to or higher than that at the time of about 20 ° C., and the sensitivity of the sensor is improved. In this case, as shown in FIG. 6 (A), a stable signal voltage is obtained, and the peak interval and amplitude value of the filtered waveform are uniform. Therefore, when this waveform is pulsed, the trigger waveform is shown in FIG. 6 (B). As shown, stable pulses are obtained, the intervals and amplitudes are uniform, and noise is not mixed in the output pulses.

  5 is an actual measurement value of the change ratio of the crest value according to the present embodiment, and almost coincides with the theoretical value indicated by the solid line in FIG. 5 when the sensor temperature is in the range of −20 ° C. to 85 ° C. . Also, the circles in FIG. 5 are actually measured values of the sensor drive voltage according to this example, and almost coincide with the theoretical values indicated by the one-dot chain line in FIG.

In this way, the sensor drive voltage for maintaining the sensitivity constant before and after the temperature change is obtained from the sensor resistance value and output to the temperature sensitive element sensor, so the sensor sensitivity is automatically adjusted even if the temperature changes. Can be maintained. As a result, in order to adjust the sensitivity of the sensor, the operator does not have to go to the installation site of the vortex flowmeter, and there is no need to interrupt the measurement by the sensor.
Further, the voltage and current of the temperature sensitive element sensor are measured, and sensor abnormality (for example, disconnection or short circuit) can be detected.
In the above embodiment, the driving voltage of the temperature sensing element is described as an example. However, the driving current of the temperature sensing element can also be obtained.

DESCRIPTION OF SYMBOLS 1 ... Detector, 2 ... Measuring tube, 3 ... Vortex generator, 4 ... Sensor housing, 5 ... Mounting cylinder, 6 ... Terminal box, 7 ... Temperature-sensitive element sensor, 10 ... Converter, 11 ... Bias inlet, 12a , 12b ... Needle valve, 13 ... Filter, 14 ... Bias outlet, 15 ... Control part, 16 ... Flow indicator, 17 ... Communication I / F, 18 ... Amplifier part, 19 ... Filter part, 20 ... Constant current circuit, DESCRIPTION OF SYMBOLS 21 ... Amplifier, 22 ... Output circuit, 23 ... Sensor voltage control circuit, 26 ... Variable BPF, 27 ... Comparator, 40 ... Resistance value calculation part, 41 ... Temperature compensation calculation part, 41a ... Resistance-temperature characteristic, 41b ... Temperature- Sensitivity characteristics, 41c ... sensitivity-sensor voltage characteristics, 41d ... temperature-sensor voltage characteristics, 42 ... drive voltage / current control section.

In order to solve the above-mentioned problem, a first technical means of the present invention is a method of driving a temperature sensing element that compensates for an output change due to a temperature characteristic of a temperature sensing element whose resistance value changes due to a temperature change. a resistance value calculation step of obtaining the resistance value of the temperature sensing element, a temperature compensation calculation step of obtaining a drive voltage or drive current before Symbol temperature sensitive device, driving for outputting a drive voltage or drive current determined the said temperature sensitive device look including a voltage or drive current control step, said temperature compensation calculation step, the temperature calculation step of determining the temperature of the temperature sensitive device based on the resistance values obtained, the said temperature sensitive device based on the temperature obtained A sensitivity calculating step for determining the sensitivity of the temperature sensing element, and the sensitivity of the temperature sensing element for maintaining the sensitivity of the temperature sensing element constant before and after the temperature change even if the ambient temperature or the temperature of the fluid to be measured changes. Elementary A compensation coefficient calculating step for obtaining a compensation coefficient for the driving voltage or driving current of the temperature sensing element from the sensitivity obtained in the sensitivity calculating step based on the relationship with the driving voltage or driving current of And a driving voltage or driving current calculating step for obtaining a driving voltage or driving current of the temperature sensitive element .

The second technical means is characterized in that the temperature sensitive element is a temperature sensitive element sensor.
A third technical means is a vortex flowmeter characterized by implementing the above-described temperature sensing element driving method.

A fourth technical means is a temperature sensing element driving device that compensates for a change in output due to a temperature characteristic of a temperature sensing element whose resistance value varies with a temperature change, and calculates a resistance value for obtaining a resistance value of the temperature sensing element. and parts, a front Symbol sense temperature compensation calculator for determining the driving voltage or the driving current of the sensing element, and a driving voltage or driving current control unit for outputting a driving voltage or a driving current obtained the said temperature sensitive device possess, The temperature compensation calculation unit obtains the temperature of the temperature sensing element based on the obtained resistance value, obtains the sensitivity of the temperature sensing element based on the obtained temperature, and changes the ambient temperature or the temperature of the fluid to be measured. However, based on the relationship between the sensitivity of the temperature sensing element for maintaining the sensitivity of the temperature sensing element constant before and after the temperature change and the driving voltage or driving current of the temperature sensing element, Driving voltage or driving voltage of the temperature sensing element Seeking compensation coefficient is obtained by and obtains the driving voltage or the driving current of the temperature sensitive device on the basis of the compensation coefficient calculated the.

Claims (5)

A temperature sensing element driving method that compensates for a change in output due to a temperature characteristic of a temperature sensing element whose resistance value changes due to a temperature change,
A resistance value calculating step for obtaining a resistance value of the temperature sensing element;
A temperature compensation calculating step for obtaining a driving voltage or a driving current of the temperature sensing element from which the output change with respect to the temperature change of the temperature sensing element is constant even if the ambient temperature or the temperature of the fluid to be measured changes from the obtained resistance value When,
A driving voltage or driving current control step of outputting the determined driving voltage or driving current to the temperature sensing element. The temperature compensation calculation step includes:
A temperature calculating step for determining the temperature of the thermosensitive element based on the determined resistance value;
A sensitivity calculating step for determining the sensitivity of the thermosensitive element based on the determined temperature;
The sensitivity of the temperature sensing element for maintaining the sensitivity of the temperature sensing element constant before and after the temperature change and the driving voltage or driving current of the temperature sensing element even if the ambient temperature or the temperature of the fluid to be measured changes. Based on the relationship, a compensation coefficient calculation step for obtaining a compensation coefficient for the drive voltage or drive current of the temperature sensing element from the sensitivity obtained in the sensitivity calculation step;
2. The temperature sensing element driving method according to claim 1, further comprising a driving voltage or driving current calculating step for obtaining a driving voltage or a driving current of the temperature sensing element based on the obtained compensation coefficient.   The temperature sensing element driving method according to claim 1, wherein the temperature sensing element is a temperature sensing element sensor. A temperature sensing element driving device that compensates for an output change due to a temperature characteristic of a temperature sensing element whose resistance value changes due to a temperature change,
A resistance value calculation unit for obtaining a resistance value of the temperature sensing element;
A temperature compensation calculation unit that obtains a driving voltage or a driving current of the temperature sensing element from which the output change with respect to the temperature change of the temperature sensing element is constant even if the ambient temperature or the temperature of the fluid to be measured changes from the obtained resistance value When,
A drive device for a temperature sensitive element, comprising: a drive voltage or drive current control unit for outputting the obtained drive voltage or drive current to the temperature sensitive element. A vortex flowmeter, wherein the temperature sensing element driving method according to any one of claims 1 to 3 is implemented.

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