JPS609711Y2 - heat flow measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat flow measuring device that measures the flow rate of heat per unit time at a measurement site in accordance with the temperature gradient present at the measurement site.

Generally, a heat flow measurement element is placed at a measurement site and changes the output voltage according to the heat flow flowing through the measurement site, for example, a group of differential thermocouples is used to detect the temperature difference between the front and back surfaces of a thin thermal resistance plate. There is a known heat flow measuring device in which a heat flow measuring element that detects the temperature of the heat resistance plate with a thermocouple is placed at the measurement site, and the heat flow per unit time flowing through the measurement site is measured. It is being

By the way, the output characteristics of a heat flow measuring element that calculates the heat flow rate Q (Kcal/77 (h) per unit time from the temperature difference between the front and back surfaces of such a thin thermal resistance plate) corresponds to the temperature difference between the front and back surfaces. Assuming that the output voltage is V2, and the output voltage corresponding to the temperature of the thermal resistance plate is ①A, it is usually expressed by the following equation.

Q=Vp (A 10 BVT)...
(1) Here, A and B are constants determined by each heat flow measuring element, and A>O, B is 0.

Equation (1) above indicates that the output characteristics of the heat flow measuring element are temperature dependent. For example, in a heat flow measuring element using rubber as a thermal resistance plate, the temperature dependence term ( BVT) is the temperature of the heat resistance plate, that is, the measured temperature is 100
It has been confirmed that when the temperature changes by degrees Celsius, the constant A changes by about 10%.

Therefore, the temperature dependence term (BVT) in equation (1) above
If the heat flow rate Q is calculated from the product of the constant A and the output voltage Vp, ignoring
The accuracy is about 0%, which is very poor accuracy.

In addition, the measurement temperature range is limited to, for example, 0 to 100°C,
Even if you try to get accurate output when the measurement temperature is 50°C, it will be +5% at 0°C.

Since a measurement error of about 15% occurs at 100° C., although this method is effective from an accuracy standpoint, it cannot avoid the practical inconvenience of being limited in the range of use.

In addition, accuracy can be ensured by measuring the output voltages of V, ,V, with a voltmeter and calculating according to equation (1) above, and the temperature measurement range is not limited. It is difficult to know Q, and there are problems such as unreliability of data due to calculation errors.

Therefore, in order to ensure measurement accuracy and measurement temperature range, an automatic calculation circuit that automatically performs the calculation of equation (1) above using a multiplication element is connected to the heat flow measurement element having the characteristics of equation (1) above. , a heat flow measuring device with a built-in automatic calculation circuit that directly indicates the desired heat flow rate Q has been considered, but such a device uses the multiplication element described above, which complicates the configuration and reduces power consumption. This has the drawback of increasing the size and increasing the price.

This invention was conceived against this background, and uses a heat flow measuring element having the characteristics shown by equation (1) above to be inexpensive and easy to operate, for example, to adjust the scale of a manual dial. Temperature correction can be performed simply by combining the values, and the calculation according to the above formula (1) can be performed without using a multiplication element to directly indicate the accurate heat flow rate Q. The object of the present invention is to provide a heat flow measuring device that can obtain heat flow on the spot and is extremely effective in spot-by-point measurement in the field.

An embodiment of this invention will be described below with reference to the drawings.

The thermocouples of the differential thermocouple group are uniformly arranged on the entire surface of a thin thermal resistance plate, and the temperature difference between the front and back surfaces of the thermal resistance plate is detected. Heat flow measuring element 1 that changes the output voltage accordingly and its heat flow measuring element 1
A temperature measuring element 2 such as a CA thermocouple that changes the output voltage according to the temperature of At the same time, an output voltage VF that changes according to the temperature of the heat flow measuring element 1, that is, a measured temperature T, is obtained from the temperature measuring element 2.

Then, the output of the heat flow measuring element 1 is inputted to the analog calculation circuit 4 via the polarity changeover switch 3, and the output of the analog calculation circuit 4 is switched to, for example, a moving coil meter 51 and the range of the meter 51 to five levels. The heat flow rate Q is input to the heat flow indicator 5 consisting of a range switch 5°, and the arithmetic circuit 4 calculates the heat flow Q based on the output voltage of the heat flow measurement element 1, and the result of the calculation is displayed on the display 5. I am trying to display it.

Further, the output of the temperature measuring element 2 is inputted to the amplifier 7 via the cold junction compensator 6, and the output of the amplifier 7 is used for range switching, for example, for switching the range of the moving coil meter 8□ and its meter 81 into two steps. The temperature of the heat flow measuring element 1, that is, the measured temperature T is input to a temperature display 8 consisting of a device 8□, and the temperature of the heat flow measuring element 1, that is, the measured temperature T is displayed on the display 8.

The analog calculation circuit 4 connects the output of the heat flow measuring element 1 to a first operational amplifier 41. The output of the first operational amplifier 411 is inputted to the second operational amplifier 41° via the first operational coefficient setting potentiometer 421, and the output of the second operational amplifier 41° is inputted to the second operational amplifier 41°. This signal is input to the third operational amplifier 413 through a voltage divider in which the operational coefficient setting potentiometer 4゜2 (voltage dividing element) and the third operational coefficient setting potentiometer 423 (temperature correction potentiometer) are connected in series. The output of the third operational amplifier 413 is input to the heat flow indicator 5, and the operational amplifier 41
Amplification degree of 1~4□3 and each potentiometer 4□1~
α is a constant determined from the total resistance value of 43, β is a constant determined from the relationship between the total resistance values of the second and third potentiometers 4°2.423, and β is a constant determined from the relationship between the total resistance values of the second and third potentiometers 4゜2.423.
Set the setting values of 1, 4□2, and 4□3 to J, L, and input voltage, respectively.

When the output voltage Vout is, Vo4 = α・J・ (β・K×L)V+−・・・・
...(2), and set the above constants α, β and each set value J? K? L is set to a predetermined value, and the output voltage (■) and the input voltage (■) of the heat flow measuring element 1 are respectively set to predetermined values.

■ When input as above output voltage.

The heat flow rate Q through which ut flows through the heat flow measurement element 1
The voltage is set to correspond to the voltage.

That is, the above analog calculation circuit 4 transforms the above equation (1) as follows: Q=BVp (A/B 10 V A) . . .
(3), and if a CA thermocouple is used as the temperature measuring element 2 that outputs the V, the measured temperature will be 0 to 300.
In the range of ℃, the measurement temperature T [℃] and the output voltage V, (mV) of the temperature measurement element 2 are VT = 0.04T...
・Since it is well approximated by (4), the above equation (4) can be replaced by the above (
3) Substituting into the equation and transforming it, Q=0.04BVF (25(A/B) +T) ・
...(5) is found.

In addition, in the above equation (5), if B<0, B =
-B'(B'> 0), Q=0.048'
Vp (25 (A/B') - T) (6) and further introduce a constant C such that A /B'≧C≧T/25, Q=0.048'Vp (25 (A/B'-C)+(2
5C-T)) ......(7) can be found, so if the constant B determined by the characteristics of the heat flow measuring element 1 is B>0, B, A/B of the above equation (5) , T
are set using the calculation coefficient setting potentiometers, and the heat flow rate Q is calculated from the above equation (5), and the above constant B is set so that B<
In the case of O, B' in the above formula (7), A/B'-C,
An arithmetic circuit that calculates the heat flow rate Q by setting each of 25C-T using an arithmetic coefficient setting potentiometer is considered.

That is, in the above equation (2), the constants α and β are each α=0.04. β = 25, and for each set value J, if L is B>O, J = B, and = A/B.
, L=T, and if B<O, J=B',
=A/B'-C9L=25c-T.

With such a configuration, when the heat flow measurement element 1 is attached to a measurement site, such as a wall surface, the heat flow measurement element 1
, the heat flow rate Q flowing through the heat flow measurement element 1
1, that is, the output voltage according to the heat flow rate Q flowing to the measurement site where the heat flow measurement element 1 is attached can be obtained.
From this, an output voltage (1) that changes depending on the temperature of the heat flow measuring element 1, that is, the measured temperature T is obtained.

Then, the output voltage Vp of the heat flow measuring element 1 is input to the analog calculation circuit 4, and the output voltage Vp of the temperature measuring element 2 becomes a thermoelectromotive force with reference to 0°C by the cold junction compensator 6, and the temperature Moving coil meter 81 of display 8
The measured temperature T is displayed in the optimum range by changing the range using the 8° range switch.

Therefore, according to the constants A and B in equation (1) above, which are determined by the output characteristics of the heat flow measuring element 1, if B>0, the first calculation coefficient setting potentiometer 421 of the calculation circuit 4
The setting value of B1 is the setting value of the second calculation coefficient setting potentiometer 4□2, and if B<0, the setting value of the first calculation coefficient setting potentiometer 4□1 is B'.
(B'=-B), the set value of the second calculation coefficient setting potentiometer 422 is set to A/B'-C (C: constant), and the measured temperature T displayed by the temperature display 8, In the case of B>O, the setting value of the third calculation coefficient setting potentiometer 423 is set to T, and in the case of B<0, the setting value of the third calculation coefficient setting potentiometer 4□3 is set to 25C-T. The output voltage ■F of the heat flow measuring element 1 can be either a positive or negative signal depending on the direction of the heat flow to be set and measured, so the polarity changeover switch 3 is used to change the polarity input to the calculation circuit 4 so that it is always constant. , the arithmetic circuit 4 calculates the output voltage V output from the heat flow measuring element 1.
If the constant B determined by the output characteristics of the heat flow measuring element 1 based on p is B>0, calculate the above equation (5),
If B<0, the above formula (7) is calculated and a voltage corresponding to the heat flow rate Q flowing to the measurement site is output, and the voltage corresponding to the heat flow rate Q output by the calculation circuit 4 is displayed as the heat flow rate. The moving coil meter 51 displays the heat flow rate Q flowing to the measurement site in the optimum range by changing the range of the range changer 5□.

In FIG. 2, the output voltage Vp of the heat flow measuring element 1 is V, = 0.
．． 5-10 (mV), constant A, B = 2-10,
An example of the measurement results corresponding to the above equation (5) when A/B=10 to 100 and the measurement temperature T is T=0 to 300 will be shown.

This measurement result shows that highly accurate measurements can be performed over a wide range.

In this way, according to the present device, the heat flow measuring element 1 having the characteristics shown by the above equation (1) is used, and the first and second calculation coefficient setting potentiometers 4 are set in advance according to the characteristics of the element 1. □□, 422 are set, and the value of the measured temperature T is transferred to the third calculation coefficient setting potentiometer 4□3.
By a simple operation of setting , the temperature of the measured value can be corrected, and the heat flow rate Q can be measured accurately.

Moreover, using the first to third calculation coefficient setting potentiometers 4□1, 4□29423, these potentiometers 421. 4□2,4. Vp(A
10B·■,) can be performed without using a multiplication element.

In other words, by replacing (A + B・V) with the partial pressure ratio of electrical resistance and dividing the output voltage 2 of the heat flow measuring element 1 by the above partial pressure ratio, it is proportional to Vp (A + B・V). output voltage can be obtained.

Therefore, the operational amplifier 411 that performs only amplification of the signal voltage in the operational circuit 4 without using a multiplication element? 41□,
413 and each potentiometer 4□1? 422?
This can be realized with a simple configuration of only 4□3.

Therefore, it is possible to reduce power consumption and price,
It can be made small and portable, and it can be extremely effective in spot-by-point measurement of heat flow in the field.

Note that the configuration of this invention is not limited to that of the above embodiment.

For example, as shown in FIG. 3, fixed resistors 4319
432 are connected in series, and each series circuit is connected in parallel to form a so-called bridge circuit, and a constant B'(B'
, = -33), the constant A/B' may be set with the second arithmetic coefficient setting potentiometer 423, and the measured temperature T may be set with the third arithmetic coefficient setting potentiometer 423. By doing so, the heat flow rate Q can be calculated using the above equation (6) in the case of B<0.

In addition, in the above embodiment, two moving coil meters are used to constantly display the measured temperature T, but by switching the input of one moving coil meter, the heat flow rate Q and the heat flow rate Q can be measured with one moving coil meter. The temperature T may be switched and displayed, and a digital voltmeter or the like may be used instead of the moving coil meter.

In addition, a continuously variable potentiometer was used to set each calculation coefficient, but it is also possible to use a potentiometer that can change the set value in stages, for example. In this case, the accuracy of temperature correction becomes poor, but there is a degree of freedom in selecting the set value for each step, which is extremely convenient for circuit adjustment.

In addition, the first and second potentiometers 4□□, 42
Since it is determined only by the element characteristics of the heat flow measuring element 1 of No. 2, a so-called voltage dividing element such as an ordinary variable resistor can be used instead.

Furthermore, the first potentiometer 421 is connected to the amplifier 41t.
, 412, 4□3 can also be removed by appropriately determining the respective amplification degrees.

In addition, in the above embodiment, the measured temperature T was directly determined and each calculation coefficient was set using the measured temperature T, but this can be done by replacing the measured temperature T with another appropriate correction value. , each calculation coefficient may be set based on the obtained correction value.

As detailed above, according to this invention, temperature correction of measured values can be performed at low cost and with simple operation using a heat flow measuring element having the characteristics shown by equation (1) above. , it is possible to directly indicate the accurate heat flow rate Q by performing the calculation according to the above formula (1) without using a multiplication element,
It is possible to provide a heat flow measuring device that makes it possible to obtain the actual heat flow rate on the spot, and is extremely effective for point-by-point spot measurements in the field.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the configuration of an embodiment of this invention;
The figure shows an example of the measurement results of the same embodiment, and FIG. 3 is a circuit diagram showing the configuration of another embodiment of the invention. 1... Heat flow measuring element, 2... Temperature measuring element, 4... Analog calculation circuit, 4゜□~4
゜3...Potentiometer for setting calculation coefficient, 5
...Heat flow indicator, 8...Temperature indicator.

Claims (1)

[Scope of utility model registration request] Voltage (2) related to the heat flow rate Q flowing through the measurement area outputted by the heat flow measurement element disposed at the measurement area, and the temperature measurement element corresponding to the temperature T of the measurement area detected by the temperature measurement element. Obtain the measured output voltage ■A,
In a heat flow measuring device that obtains an indication value corresponding to the heat flow rate Q from these voltages V, V1, the coefficient of the temperature T and its output voltage (2) is set to 1 to determine the heat flow rate of the heat flow measuring element die. When the detection coefficient for Q is A1 and the temperature dependence coefficient for the temperature output VT of the heat flow measuring element is B, then after amplifying the voltage 2 with an amplification degree of BK, this amplified output voltage is given a weight of A/BK. It is taken out as a divided output voltage through the set first potentiometer and the second potentiometer whose weight is set as T, and VFBK (q+') corresponding to the heat flow rate Q is taken out as the potential difference between these divided output voltages. A heat flow measuring device characterized in that it obtains an indicated value of r).