JPH0210445Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an absolute hygrometer that electrically measures absolute humidity. Conventional absolute hygrometers include, for example, absorption hygrometers, which pass a certain amount of air through a U-shaped tube containing phosphorus pentoxide, absorb all the water vapor contained in the air into phosphorus pentoxide, and absorb phosphorus pentoxide. Since the absolute humidity is determined by measuring the increase in the mass of the air, it has the drawback of being complicated to operate.
Furthermore, when using a psychrometric bulb type hygrometer, a hair hygrometer, etc., there is a drawback that absolute humidity cannot be directly read. The present invention improves the above-mentioned drawbacks, and its purpose is to enable direct reading of absolute humidity with a simple configuration. Examples will be described in detail below. FIG. 1 is an explanatory diagram of an embodiment of the present invention, showing a thermistor, platinum, or other sensitive element R _s held in such a way that it can freely contact the outside air, and a thermistor, platinum, etc. held in an absolutely dry state. Temperature compensation element R _c and 2
a bridge circuit consisting of two resistors R ₂ and R ₃ and a variable resistor R ₄ for zero point adjustment; a power source E connected to this bridge circuit via a current control resistor R ₁ ;
It consists of an amplifier 1 that amplifies the bridge unbalanced output voltage appearing between terminals T ₁ and T ₂ and a voltmeter 2 that measures the output voltage of this temperature compensation amplifier 1. The heat-sensitive element R _s used in this example is
For example, it has the structure shown in Figure 2, where 3 is a thermistor with a glass coating, 4 is a metal cap, 5 is a hermetic seal, 6 and 6' are lead wires, and 7 is a hole. It is. The metal cap 4 is hermetically sealed by a hermetic seal 5, but a hole 7 with a diameter of, for example, about 0.5 mm is inserted into the metal cap 4.
The thermistor 3 can be brought into contact with the outside air. On the other hand, since the temperature compensating element R _c needs to be kept in an absolutely dry state, the metal cap of the heat sensitive element R _s shown in FIG. 2 is not provided with the hole 7. However, it is necessary that the heat-sensitive element R _s and the temperature-compensating element R _c have almost the same current-voltage characteristics, and that they are placed close to each other in an atmosphere of zero relative humidity. It is necessary to maintain the same temperature. When measuring absolute humidity using the absolute hygrometer shown in Fig. 1, as an initial adjustment, first hold the heat-sensitive element R _s in an atmosphere of zero relative humidity, and apply a voltage from the power supply E to the heat-sensitive element R s. The element R _s and the temperature compensation element R _c are brought into a self-heating state (approximately 200° C.), and then the variable resistor R ₄ is adjusted so that the bridge unbalanced output voltage appearing across the resistor R ₅ becomes zero. After the initial adjustment is completed, the heat-sensitive element R _s is brought into contact with the outside air and measurement of absolute humidity is started. heat sensitive element
When R _s is brought into contact with the outside air, when the amount of water vapor contained in the outside air is large, that is, when the absolute humidity is high, the heat radiation amount of the heat-sensitive element R _s increases, and its temperature decreases. Although this temperature drop is very small, the bridge circuit loses its balance and a bridge unbalanced output voltage occurs between terminals T ₁ and T ₂ . This bridge unbalanced output voltage changes in response to the absolute humidity of the outside air, as shown in the experimental results described below. Therefore, the bridge unbalanced output voltage is amplified by amplifier 1, and this is measured by a voltmeter. 2, the absolute humidity can be determined. Also, in this case, the absolute humidity is
Since it shows the amount of water vapor contained in 1 ^m3 of outside air, if you display the dew point corresponding to this absolute humidity in addition to the absolute humidity on the scale of voltmeter 2, you can easily measure the humidity in the atmosphere. The dew point can be easily determined. Below are the experimental results for determining the relationship between bridge unbalanced output voltage and absolute humidity. [1] In the circuit shown in Figure 1, the heat-sensitive element
R _s , when a thermistor is used as the temperature compensation element R _c In this case, the thermistor has a current of -
It has voltage characteristics (at an ambient temperature of 25° C.), and FIG. 3 is a characteristic diagram plotting Table 1.

[Table] Also, the resistances R ₁ to R ₃ and R ₅ are each 0.389KΩ,
Use 10.04KΩ, 10.04KΩ, 49.47KΩ,
A 9.88V power supply E was used. At this time, the current flowing through the heat-sensitive element R _s was 14.98 mA at an ambient temperature of 10°C. In this way, while setting the constants of each part, and setting the heat-sensitive element R _s and the temperature-compensating element R _s to the above-mentioned self-heating state, we can calculate the relationship between the bridge unbalanced output voltage appearing across the resistor R ₅ and the relative humidity using the temperature as a parameter. The relationship was measured and is illustrated in FIG. 4, and Table 2 shown below shows part of this measured data.

【table】

[Table] Next, when the relationship between temperature, absolute humidity, and bridge unbalanced output voltage is determined based on the measurement results shown in FIG. 4, the relationships shown in Table 3 are obtained.

【table】

[Table] Also, based on this Table 3, at each temperature,
Table 4 shows how much the bridge unbalanced output voltage increases each time the absolute humidity increases by 1 g/m ³ .

[Table] As shown in Table 4, the thermistor is a heat-sensitive element,
When used as a temperature compensation element, the bridge unbalanced output voltage exhibits an approximately equal rate of increase with increase in absolute humidity at each temperature. Therefore, by measuring the bridge unbalanced output voltage, the absolute humidity can be directly read regardless of the outside temperature. [2] In the circuit shown in Figure 5, the heat-sensitive element
When platinum elements are used as R′ _s and temperature compensation element R′ _c , in this case, the platinum elements used as heat sensitive element R′ _s and temperature compensation element R′ _c are shown in Tables 5 and 6, respectively. Current-voltage characteristics (at an ambient temperature of 25°C)
Figures 6 and 7 are shown in Table 5.
FIG. 6 is a characteristic diagram plotting Table 6.

【table】

[Table] Also, resistances R ₆ and R ₇ are 1025.62Ω and 922.2Ω, respectively.
The heat-sensitive element R′ _s and the temperature-compensating element R′ _c
The power supply E' was adjusted so that a current of 130 mA constantly flows through the terminal. In this way, while setting the constants of each part, setting the heat-sensitive element R's and temperature compensation element R'c in a self-heating state (approximately 200℃), and setting the temperature as a parameter, the terminal
Figure 8 shows the measured relationship between the bridge unbalanced output voltage appearing between T' ₁ and T' ₂ and the relative humidity, and Table 7 below shows part of this measured data. This is what is shown.

[Table] Next, based on the experimental results shown in Table 7, the relationships between temperature, absolute humidity, and bridge unbalanced output voltage are determined, and the relationships shown in Table 8 are obtained.

【table】

[Table] Also, based on this Table 8, if we calculate how much the bridge unbalanced output increases for every 1g/ ^m3 increase in absolute humidity at each temperature, we will get the results shown in Table 9. .

[Table] When a platinum element is used as the heat-sensitive element R' _s and the temperature-compensating element R' _c , the rate of increase in the bridge unbalanced output voltage differs at each temperature, as shown in Table 9. Become. However, at one temperature point, the bridge unbalanced output voltage changes in proportion to changes in absolute humidity, so if it is used in an atmosphere where the ambient temperature is always constant, the bridge unbalanced output voltage By measuring the absolute humidity, you can directly read the absolute humidity. In addition, in order to be able to directly read the absolute humidity regardless of the ambient temperature, a temperature compensation amplifier whose amplification factor changes in response to changes in temperature is connected to terminals T' ₁ and T' ₂ . The rate of increase in the output voltage from the compensation amplifier may be made constant regardless of the ambient temperature. FIG. 9 is a circuit diagram showing an example of a temperature compensation amplifier, in which OP is an operational amplifier, Th
is a thermistor, R ₈ to R ₁₄ are resistors, C is a capacitor, and Tout is an output terminal. In this case, since the thermistor Th is connected to the feedback circuit of the operational amplifier OP, the amplification factor of the operational amplifier OP changes in response to changes in the ambient temperature. Therefore, the output terminal Tout
It becomes possible to keep the rate of increase in the output voltage from It goes without saying that the temperature compensation amplifier may be of any type as long as it can achieve the above purpose. Also, when using a thermistor as a heat-sensitive element or temperature-compensating element, if such a temperature-compensating amplifier is used,
Measurement accuracy can be increased. As explained above, the present invention is based on a bridge circuit consisting of a heat-sensitive element held so as to be in contact with the outside air, a temperature compensation element kept in an absolutely dry state, and two resistors. The absolute humidity of the outside air is measured by measuring the bridge unbalanced output voltage, and if the heat-sensitive element and temperature compensation element are appropriately selected, the bridge unbalanced output voltage will be as shown in the experimental results described above. Another advantage is that if the absolute humidity is constant, it will be a constant value regardless of the temperature of the outside air, so the absolute humidity can be read directly with a simple configuration. Also, as mentioned above,
If the absolute humidity is determined, the dew point of the humidity measurement atmosphere can be easily determined, which is extremely effective industrially.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of the present invention, Fig. 2 is a structural diagram showing an example of the structure of a heat-sensitive element, Fig. 3 is a characteristic diagram showing the current-voltage characteristics of a thermistor, Fig. 4,
Figure 8 is a characteristic diagram showing the relationship between temperature, relative humidity, and output voltage, Figure 5 is a circuit diagram of the circuit used in the experiment, and Figures 6 and 7 are characteristics showing the current-voltage characteristics of platinum. 9 are circuit diagrams showing an example of a temperature compensation amplifier. R _s and R′ _s are heat sensitive elements, R _c and R′ _c are temperature compensation elements,
R ₁ to R ₁₄ are resistors, E and E' are power supplies, OP is operational amplifier, Th is thermistor, C is capacitor, 1 is amplifier, 2 is voltmeter, 3 is thermistor, 4 is metal cap, 5 is hermetic 6 and 6' are lead wires, and 7 is a hole.

Claims (1)

[Claims for Utility Model Registration] Two heat-sensitive elements: a heat-sensitive element held so as to be in contact with the outside air, and a temperature-compensated element that has almost the same resistance-temperature characteristics as the heat-sensitive element and is kept in an absolutely dry state. A resistor and a variable resistor connected in series with the one resistor are bridge-connected, and a current is passed through the heat-sensitive element and the temperature-compensating element so as to heat the element to a temperature higher than the outside temperature, thereby outputting an unbalanced voltage. It consists of an absolute humidity measuring circuit consisting of a bridge circuit, and an amplifier whose output is divided by a voltage dividing circuit consisting of a thermistor and a resistor and fed back to the input side.It converts an input voltage with temperature characteristics into an output voltage independent of the ambient temperature. and a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit that obtains a temperature compensation circuit of An absolute hygrometer characterized by obtaining an output voltage corresponding to absolute humidity.