JPS6150249B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a temperature measuring method that utilizes the resistance-temperature characteristics of platinum resistors. Conventionally, there is a resistance thermometer that uses a platinum resistor as a resistance thermometer that makes use of the change in resistance of a temperature measuring resistor with a large temperature coefficient. For example, as shown in Figure 1, constant resistance
The temperature is detected by applying a power supply voltage ν to a series circuit of R ₁ and a platinum resistor R ₂ and measuring the voltage E across the platinum resistor R ₂ . However, the resistance temperature characteristics of platinum resistor R ₂ are nonlinear, as shown in Table 1 on the separate sheet. Therefore, in order to make each characteristic value correspond to the measured temperature, subtract the resistance value R ₂₀ = 10000Ω of the platinum resistor R ₂ at 0°C, and multiply by 400/149.56 to match the value at 400°C. Even so, there will be an error of several percent. The maximum error is −8.13 at −100°C
There is an Ω. Further, the resistance change value ΔR (Ω) at 50°C intervals also shows a variation close to 2Ω. Therefore, it was not possible to directly know the temperature from this measured resistance value. Furthermore, if the power supply voltage ν varies in the circuit of FIG. 1, the measured value will be directly affected in proportion to this, making it impossible to measure accurately. Furthermore, when using this resistance thermometer to digitize and display the measured quantity by applying an A-D converter, a reference voltage is required. However, if this reference voltage changes, accurate digitization cannot be performed, so it is necessary to devise a circuit for stabilizing the reference voltage, which inevitably complicates the digitization circuit. Therefore, in view of the above-mentioned drawbacks, the present invention aims to improve and eliminate this by providing a first series circuit in which a constant resistor R ₁ and a platinum resistor R ₂ are connected in series, as shown in FIG. A T-shaped circuit in which one ends of three constant resistors R ₃ , R ₄ , R ₅ are commonly connected, and a constant resistor R ₆ ,
A temperature measuring circuit is constructed by connecting second series circuits each having R ₇ connected in series in parallel, and applying a power supply voltage ν to the second series circuits. That is, the constant resistance R ₁ of the circuit shown in FIG.
Select the values of R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ appropriately, and calculate the potential difference (e ₂ − e ₀ ) between the midpoint of the second series circuit and the potential at the midpoint of the first series circuit. , the potential difference at the common connection point of the T-shaped circuit with respect to the potential at the midpoint of the first series circuit.

[Table] Calculating the loop currents i ₁ , i ₂ , i ₃ from this formula: △=(R ₁ +R ₂ ) (R ₁ +R ₃ +R ₄ ) (R ₂ +R ₃ +R ₅ ) −2R ₁ R ₂ R ₃ −R ² ₂ (R ₁ +R ₃ +R ₄ ) −R ² ₃ (R ₁ +R ₂ ) −R ² ₁ (R ₂ +R ₃ +R ₅ ) =R ₂ {(R ₁ +R ₃ )(R ₄ +R ₅ )+R ₄ R ₅ } +R ₁ (R ₃ +R ₄ )(R ₃ +R ₅ ) −R ₁ R ² ₃ + R ₁ {R ₃ (R ₄ + R ₅ ) + R ₄ R ₅ }…(d) ∴i ₁ = ν｛R ₂ (R ₁ + R ₃ + R ₄ ) + (R ₃ + R ₅ ) ( R ₁ + R ₃ + R ₄ ) − R ² ₃ }/△ …(e) i ₂ = ν｜R ₂ (R ₁ + R ₃ ) + R ₁ (R ₃ + R ₅ )}/△
…(f) i ₃ = ν{R ₂ (R ₁ + R ₃ + R ₄ ) + R ₁ R ₃ }/△ …(g) Here, the values of constant resistances R ₁ , R ₃ , R ₄ , R ₅ and the power supply The value of voltage ν is set as follows. R ₁ = 1.3KΩ, R ₃ = 510Ω, R ₄ = _5.1KΩ R ₅ = 10KΩ, ν = 2600V ) was used to obtain the results shown in Table 2 for each temperature. That is, read the resistance change of the platinum resistor _R2 at each temperature t (℃) from Table 1, and calculate the loop current.
Calculate i ₁ and i ₃ . Based on this current value, the platinum resistance R ₂
The voltage e ₂ across the constant resistor R 5 and the voltage e ₁ across the constant resistor R ₅ are determined. Next, in order to make the voltage e ₂ at 0°C correspond to 0°C, let the voltage 221.56mV at this time be e ₀ , calculate (e ₂ - e ₀ ) for each temperature, and convert this into A. shall be. Further, the potential difference (e ₂ −e ₁ ) between the voltages e ₂ and e ₁ is calculated for each temperature, and this is defined as B. Then, divide A by B to obtain A/B. Next, in order to match the A/B value to the measured temperature, the value at 400℃ -
Based on 1.6260, A/B value of each temperature is 400/1.62
Multiply by 60. A/ obtained in this way
Comparing the value of B.400/1.6260 with the value of t (°C) at the left end of Table 1, it is found that they are very close to each other, with a maximum error of 0.11°C, and can be read directly as is for practical use. By the way, in this calculation example, in order to correct the measured voltage (e ₂ − e ₀ ) at 0°C to ₀ mV,
Calculated as = 221.56mV. Therefore, when the power supply voltage ν is 2600V, the value of e ₀ is set to 221.56 mV, and a circuit that can also compensate for fluctuations in the power supply voltage ν is considered. That is, a second series circuit consisting of a resistor R ₆ and a resistor R ₇ is connected to the power supply voltage ν as shown in FIG. 3, and the voltage at the midpoint is taken out as e ₀ . In the circuit of FIG. 3 configured in this way, the voltage at the midpoint of the first series circuit is
The potential difference (e ₂ −e ₀ ) at the midpoint of the series circuit is divided by the potential difference (e ₂ −e ₁ ) at the common connection point of the T-shaped circuit with respect to the voltage at the midpoint of the first series circuit. This quotient e ₂ −e ₀ /
It can be seen that e ₂ −e ₁ has a value that is independent of the power supply voltage ν, as will be explained next, and is not affected by fluctuations in the power supply voltage ν. That is, in FIG. 3, e ₂ −e ₀ =ν(R ₂ /R ₁ +R ₂ −R ₇ /R ₆ +R ₇ ) Also, according to the above equations (d)(f)(g), e ₂ −e ₁ = R ₃ (i ₃ − i ₂ ) = νR ₃ (R ₂ R ₄ − R ₁ R ₅ )/△ Therefore, e ₂ − e ₀ / e ₂ − e ₁ = (R ₂ / R ₁ + R ₂ − R ₇ /R ₆ +R ₇ )Δ/R ₃ (R ₂ R ₄ −R ₁ R ₅ ). This is a value that is independent of the power supply voltage ν, and can be accurately measured without being affected by its fluctuations. In addition, when dividing the potential difference (e ₂ − e ₀ ) by the potential difference (e ₂ − e ₁ ) in temperature measurement using this configuration circuit, LSI
Division and its digital display can be easily performed by using A-D converters, which are now available in a variety of types. That is, as shown in FIG. 3, the potential difference between the dividends (e ₂ -e ₀ ) is used as the input voltage of the AD converter 1, and the potential difference between the divisors (e ₂ -e ₁ ) is used as its reference voltage. The output can then be read on the digital display 2. In this way, there is no need to consider measurement errors due to fluctuations in the reference voltage.
Accurate measurements are possible with an inexpensive configuration. As explained above, the present invention includes a first series circuit in which a constant resistor and a platinum resistor are connected in series, a T-type circuit in which one ends of three constant resistors are connected in common, and a T-type circuit in which two constant resistors are connected in series. and a second series circuit connected in series, and T is provided at both ends and at the midpoint of the first series circuit.
The three terminals of the type circuit are connected respectively, the second series circuit is connected in parallel to both ends of the first series circuit, and a power supply voltage is applied. The potential difference at the midpoint of the series circuit of
Since we have provided a temperature measurement method that measures the temperature of a platinum resistor by dividing it by the potential difference between the midpoint of the series circuit and the common connection point of the T-type circuit, we can compensate for the nonlinear resistance-temperature characteristics of the platinum resistor for temperature measurement. The temperature of the platinum resistor can be measured without being affected by fluctuations in the power supply voltage. Direct reading of the temperature is therefore possible, the need for difficult and expensive power supply stabilization is eliminated, and the divisor voltage difference (e ₂ −e ₁ ) is
can be applied to the reference voltage for AD conversion, making it possible to construct a simple and inexpensive circuit.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an example of conventional temperature measurement, FIG. 2 is an electric circuit diagram explaining the functions of the main components of this invention, and FIG. 3 is an electric circuit diagram of an embodiment of this invention. . ν...Power supply voltage, e ₀ ... Voltage at the midpoint of the second series circuit, e ₁ ... Voltage at the common connection point of the T-type circuit, e ₂
...The voltage at the midpoint of the first series circuit, R ₁ , R ₃ ,
R ₄ , R ₅ , R ₆ , R ₇ ... constant resistance, R ₂ ... platinum resistance.

【table】

【table】

Claims (1)

[Claims] 1. A first series circuit in which a constant resistor and a platinum resistor are connected in series, a T-shaped circuit in which one ends of three constant resistors are connected in common, and a second series circuit in which two constant resistors are connected in series. The three terminals of the T-type circuit are connected to both ends and the middle point of the first series circuit, the second series circuit is connected in parallel to both ends of the first series circuit, and the power supply voltage is Configure by applying
Measure the temperature of the platinum resistor by dividing the potential difference between the midpoint of the first series circuit and the midpoint of the second series circuit by the potential difference between the midpoint of the first series circuit and the common connection point of the T-shaped circuit. A temperature measuring method characterized by: