An electric hygro-permeameter is effectively applicable to measure the permeability of moisture of various kinds of materials in sheet form.
As the anti-moisture properties are very important for packing materials the electric hygro-permeameter given in this article was applied to measure the moisture permeability of these materials. This measuring method makes it possible to observe moisture penetration moment by moment and to judge the degree of moisture permeability of a sample material within only one hour, the time equivalent to one seventieth of that required in ordinary weighing method.

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In measuring frequency, an indirect method have usually been taken. In this method, there are two ways ordinarily, one is by applying the principle of mechanical or electrical resonance and another by applying variation of reactance due to transition of frequency. However, it goes without saying that frequency can also be measured by a direct method in Which there are two ways too. Namely, according to the definition of frequency:
Frequency=a number of cycles/time taken to complete the cycles of the numerator
Therefore, in direct measurement of frequency, the following two ways are employed:
1) To count the number of cycles in a certain time.
2) To measure the time in a given number of cycles. Comparing each of the above two in the point of accuracy and measuring time, it is believed that the former is more advantageous in measuring high frequency but disadvantageous in measuring frequency and the latter is just contrary. Generally, electronic frequency measuring devices familier to us employ the Item 1) and the devices employed the Item 2) have never been seen.
Given in this paper is the "Frequency Measuring Device" which employs the above mentioned Item 2). Experimental data are also given with the description that this kind of frequency measuring device can easily obtain high accuracy especially in measuring low frequency.

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The pulsating gas flow meter proposed by one of the authors in a previous paper was developed into a commercial instrument and was practically tested under various experimental conditions. It is provided with a small orifice, through which clean dry air is made to flow by automatically applying to the orifice the same upstream and downstream pressures as those produced in a main orifice by a pulsating gas flow to be measured. Thus simulated air flow is read, after its pulsation is eliminated, by means of a capillary tube or an orifice with differential, pressure recorder. Practical tests were performed by comparing the two values, one read by this flow meter and another obtained by an ordinary orifice flow meter, with those determined by a gas holder method. Pulsation waveform oscillograms were taken at the same time. As a result, the readings of this flow meter were found to be in close coincidence with those determined by the gas holder method under moderate pulsating conditions, while errors of several percents of an ordinary flow meter were observed. By these tests, the instrument was proved to be quite useful for practical purposes. Here are given two actual cases in ammonia synthesis plants, where an instrument installed to measure the gas flow carrying severe pulsation caused by a compressor suction has been practically used for these one or two years without trouble.

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Having investigated an availability of testing methods for a large-capacity gas meter, the authors manufactured by way of trial a testing equipment for flow rates up to 200m³/h, which consists of a standard wet gas meter, changing valve and collapsible gas container which is made of compound rubber and has a capacity of about 5m³. Since its accuracy was found to be about ±0.1% from the result of experiments, they maufactured a larger testing equipment having a maximum capacity of about 30m3 and confirmed that it goes satisfactory even for larger flow rates up to 1500m³/h.

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