JPS6116017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wet and dry bulb hygrometer using an electric thermometer, that is, a hygrometer that calculates relative humidity by processing signals from a dry bulb thermometer and a wet bulb thermometer. .

Conventionally, in a computing unit that calculates the relative humidity H in this type of hygrometer, the detected dry bulb temperature T _D
The circuit configuration was such that the relative humidity was calculated using various calculation methods based on the difference between the temperature and the wet bulb temperature T _W .

However, in arithmetic units using such conventional calculation methods, the measurement range within which the error is within ±2% is narrow, as shown by the broken line in FIG. In particular, the larger the wet-dry bulb difference, the more ±2% of the difference.
There was a problem in that it became difficult to measure within the range.

In view of the above points, the present invention provides a dry bulb temperature T _D
A circuit is constructed that divides two linear equations with two variables and the wet bulb temperature T _W , and over a wide range,
The object of the present invention is to provide a hygrometer that can perform measurements with higher precision.

Next, an embodiment of a hygrometer according to the present invention will be described with reference to the drawings.

In the figure, 1 is the dry bulb input terminal that is connected to a dry bulb thermometer such as a resistance thermometer, and this terminal 1 is the dry bulb side that includes a temperature signal to electrical signal converter such as a resistance to voltage converter, and a linearizer. It is connected to the preamplifier 2, and 3 is a wet bulb input terminal that is connected to a wet bulb temperature measuring device such as a resistance thermometer. It is connected to the wet bulb side preamplifier 4 which includes. Thus, the dry bulb temperature T _D is output from the dry bulb side preamplifier 2, the wet bulb temperature T _W is output from the wet bulb side preamplifier 4, and the dry bulb temperature T _D output is directly applied to the output terminal 5. together with the coefficient
The output of the wet bulb side preamplifier ₄ is added to the adder 7 via the K4 setting _resistor R4, and the output of the wet bulb side preamplifier 4 is added to the adder 7 via the _K5 setting resistor _R5.
A coefficient K ₆ is added through the resistor R ₆ . In this way, from the adder 7
A value that can be expressed by the formula K ₄ T _D +K ₅ T _W +K ₆ is output, and this output value is input to the numerator term input terminal of the divider (division means) 8. On the other hand, the above _- mentioned dry bulb _{temperature T
The W} output is applied via a coefficient K ₂ setting resistor R ₂ and a coefficient K ₃ is applied from a resistor R ₃ . In this way, from the adder 9, K ₁ T _D +K ₂ T _W +K ₃
A value that can be expressed by the following formula is output, and this output value is input to the denominator input terminal of the divider 8. Therefore, each of the above two-variable linear expressions is divided by the divider 8, and the divider 8 calculates H=(K ₄ T _D +
An output value expressed by the formula K ₅ T _W +K ₆ )/(K ₁ T _D +K ₂ T _W +K ₃ ) is output. This output value is output from the relative humidity output terminal 11.

The above coefficients _K1 to _K6 are set by circuit constants such as resistors _R1 to _R6 , and in this example, _K1 = 0.157, _K2 = -0.089, _K3 = 1, _K4 =
-8.32, K ₅ = 15.06, K ₆ = 103.6. Note that the first addition means, second addition means, and calculation means may be replaced with known digital circuits, such as microcomputers.

The accuracy when actually measuring with the hygrometer having the above configuration will be explained with reference to the chart in FIG.

The chart in FIG. 2 shows the actual relative humidity value determined by the Assmann characteristic dry bulb temperature T _D and the wet and dry bulb difference, and when measured using the hygrometer according to the present invention, It was confirmed that the error was within ±1% within the range enclosed by the thick line in the table. In other words, if we compare this range (thick line) with the inner range surrounded by the broken line (the measurement range where the conventional error is within ±2%), the measurement range and measurement accuracy according to the present invention are greater than the conventional range. Expanding and improving. In particular, this measurement range expands significantly where the wet and dry bulb difference is large. In addition, the above error is 1
% or less can be shifted by varying the humidity values used for sampling when setting the coefficients K ₁ to K ₆ , and the accuracy in the low temperature region or high temperature region can be particularly improved.

Further, in the above embodiments, a resistance thermometer is used as the temperature measuring element, but a thermocouple, a thermistor, etc. can be used instead of the resistance thermometer.

As _explained above, according to _the present invention, 2
Since the hygrometer has a circuit configuration that divides two equations, the measurement accuracy is further improved, and the error is ±1 as shown in Figure 2, especially in areas where the wet/dry bulb difference is large.
This has the effect of expanding the measurement range within %. Further, according to the present invention, since the configuration of the arithmetic circuit is simplified, it is possible to reduce the cost of the hygrometer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a hygrometer according to the present invention, and FIG. 2 is a chart showing the accuracy of the hygrometer of the present invention and a conventional hygrometer. 7...Second addition means, 8...Division means, 9...First
addition means, K ₁ to K ₆ ... coefficients.

Claims (1)

[Claims] 1. A hygrometer that obtains relative humidity H by processing a signal from a dry bulb thermometer that measures dry bulb temperature T _D and a signal from a wet bulb thermometer that measures wet bulb temperature T _W , at least Above dry bulb temperature T _D and wet bulb temperature T _W
A first addition means that performs an addition operation of K ₁ T _D +K ₂ T _W +K ₃ from a signal of , a second addition means that performs an addition operation of K ₄ T _D +K ₅ T _W +K ₆ , and From the outputs from the first and second addition means, the above relative humidity H=K ₄ T _D +
K ₅ T _W +K ₆ /(K ₁ T _D +K ₂ T _W +K ₃ ) (where K ₁ to K ₆ are coefficients). Hygrometer.