JPS6117412Y2 - - Google Patents

Description

[Detailed description of the invention] The development of air conditioning equipment has become a major issue from a wide variety of viewpoints, including not only the demand for environmental improvement, but also energy saving, resource saving, and quality control.

However, the development of such a device has been delayed due to the lack of a humidity measuring device that can accurately detect humidity and has excellent durability.

One known humidity detection method is to use a metal oxide semiconductor and apply the change in resistance due to humidity. However, despite much research, it is still not reliable. It has not been established as a reliable humidity detection method.

As a result of intensive study, the inventors of the present invention succeeded in putting a reliable humidity measuring device into practical use by using a heater and a fan in combination.

The resistance value of metal oxide semiconductors changes due to the adsorption/desorption phenomenon of water molecules on the surface, and the adsorption phenomenon is accompanied by changes over time. That is, the resistance value generally changes depending on the relative humidity and the elapsed time, and even under the same humidity conditions, the resistance value drifts toward a higher resistance side with time.

This phenomenon is caused by changes in the adsorption structure on the surface,
This is thought to be a change in the band structure of the metal oxide. Therefore, in order to perform reliable humidity detection, it is necessary to maintain a constant adsorption state of water molecules on the surface.

In addition, the drift phenomenon increases as the relative humidity increases, and in high humidity regions, continuous measurement time is limited to 10
Since it takes less than a minute, it is necessary to take measures according to the humidity.

In order to keep the element surface constant, a conventional method of desorbing surface adsorbed moisture using a heater is appropriate, and subsequent humidity detection in an adsorption equilibrium state can be considered.

However, in this case, since the element itself is also heated, it takes time for the element temperature to return to the same level as the measurement conditions.

Especially when there is no airflow, such as indoors.
It takes several minutes, and humidity cannot be detected during that time.

It is predicted that humidity detection in a stationary room such as an air conditioner or a refrigerator will become increasingly required in the future, and humidity detection within 3 minutes is required for humidity control.

The present invention was developed in view of this situation, and it is equipped with a heater for heating and refreshing the element and a cooling fan, and after heating the element and removing moisture, it can be quickly brought to the same level as the measurement conditions. This device has been devised to allow the device to return to its original state, making it possible to shorten the return time of the element to within two minutes, and making it possible to detect humidity with high precision at fixed time intervals.

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention, in which 1 is a humidity sensor made of a metal oxide semiconductor. An alternating current voltage is applied to the humidity sensor 1 by an oscillator 2, and the detected voltage proportional to humidity is amplified by an amplifier 3, and the humidity is outputted through a humidity compensation circuit 4, a linear conversion circuit 5, and an A-D conversion circuit 6. The humidity is converted into a digital signal proportional to the humidity, and the digital display device 7 is driven to digitally display the humidity. 8 is a humidity compensation thermistor provided in parallel with the humidity sensor 1.

Reference numeral 9 denotes a heater installed in parallel with the humidity sensor 1. When the refresh switch 10 is turned on, the switch 12 controlled by the heater control circuit 11 is turned on, the heater power supply circuit is closed, and the humidity sensor 1 is heated. and refresh. Note that 13 is an AC power source.

When the ambient temperature of the humidity sensor 1 reaches the set temperature, for example 150°, the comparator 14 detects this and operates the heater control circuit 11 and fan motor control circuit 15 to open the heater power supply circuit and turn off the fan. 16 for a certain period of time, humidity sensor 1
Reduce the ambient temperature to the measurement temperature.

That is, when the switch 10 is turned on, the humidity sensor 1
is refreshed.

As described above, according to this device, the humidity sensor 1 can be maintained in an optimal state at all times, so highly accurate humidity measurement can be performed at any location, and its practical value is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. 1... Humidity sensor, 2... Oscillator, 3... Amplifier, 4... Temperature compensation circuit, 5... Linear conversion circuit,
6...A-D conversion circuit, 7...Digital display device, 8...Temperature compensation thermistor, 9...Heater, 10...Refresh switch, 11...
Heater control circuit, 12... switch, 13... AC power supply, 14... comparator, 15... fan motor control circuit, 16... fan.

Claims (1)

[Scope of utility model registration request] A humidity measuring device using a metal oxide semiconductor as a sensor, characterized in that the sensor heating and refreshing heater and the cooling fan are arranged in parallel.