JPH0562934B2 - - Google Patents

Description

[Detailed description of the invention]

[Summary] In an equilibrium moisture measuring device in which a measuring means is housed in an airtight container, by coating the inner wall surface of the airtight container, the measuring means, and the electric wire between the external circuit with a hydrophobic fluororesin, the inside of the airtight container can be In addition to the sample, the length of the member that adsorbs water vapor is made as short as possible so that the equilibrium moisture content can be measured in a short time. [Industrial Field of Application] The present invention relates to an equilibrium moisture measuring device. Knowing the amount of moisture that a sample can contain at a given temperature is important, for example, for tobacco manufacturers to control the quality of leaf tobacco, and for this purpose the equilibrium moisture content of tobacco leaves is measured. . [Prior Art] Conventionally, this type of device includes a lever that is displaced by the weight of a sample, a displacement sensor that detects the displacement of the lever, and a displacement sensor that reduces the displacement of the lever to zero according to the output of the displacement sensor. A measuring means having a coil through which a current that generates a magnetic force flows, and measuring the weight of the sample by the current flowing through the coil, is housed in an airtight container in which the internal temperature and water vapor pressure can be set. After drying the tobacco leaf sample until there is no weight fluctuation, the container is kept at a predetermined temperature and water vapor is introduced into the container.The pressure is measured by a pressure sensor and set to the measured pressure. Some methods measure the equilibrium moisture content of a sample at a predetermined relative temperature based on the temperature, pressure, and weight at the time when the pressure and weight of the sample become constant and equilibrium is reached. Equilibrium moisture and relative humidity can be determined as follows. Now, let Mc be the dry weight of the sample, and M be the weight of the sample at equilibrium during the equilibrium moisture measurement operation. Furthermore, if the temperature at equilibrium during the equilibrium moisture measurement operation is T, the saturated water vapor pressure with respect to temperature T is Po, and the internal pressure inside the container at equilibrium during the equilibrium moisture measurement operation is P, then at equilibrium during the equilibrium moisture measurement operation, Equilibrium moisture W and relative humidity F are respectively W=M-Mc/Mc×100 (1) F=P/Po×100 (2) By measuring M, Mc, P, and T, the relative humidity of the sample can be determined. Equilibrium moisture W at F can be determined. [Problems to be solved by the invention] However, with conventional devices, when measuring the equilibrium moisture content of a sample, it takes a long time until the water vapor pressure in the container becomes constant and the equilibrium moisture content can be calculated. It was hot. For example, when the sample to be measured is chopped Burley tobacco with a dry weight of 1.0 g, when it is placed in a container of a certain device, the water vapor pressure in the container at the time of equilibrium moisture measurement is as shown by curve A in Figure 5. It actually takes several hours for the water vapor pressure to change and become constant.
For this reason, when trying to measure the equilibrium moisture content of one type of sample at multiple relative humidities, there was a problem in that it took many days to complete the measurement. Therefore, as a result of various experiments and studies, the inventor of the present application found that the reason why it takes a long time to equilibrate is not because it takes a long time for the sample to adsorb water vapor and equilibrate, but because the inner wall surface of the container that makes up the apparatus They discovered that this is because electrical wires and other objects continue to absorb water vapor. The experimental data that triggered this discovery is curve A in FIG. 4, which shows the temporal change in water vapor pressure when water vapor is introduced into a container in the absence of a measurement sample. That is, from curve A in FIG. 4, it can be seen that the water vapor pressure gradually decreases over time even though there is no sample, and that there is something else in the container that adsorbs water vapor other than the sample. In order to find out what is it that adsorbs this water vapor, we measured the amount of water adsorption in each part of the container when water vapor was introduced at a predetermined temperature and water vapor pressure, and calculated its contribution rate. The results shown in the table below were obtained.

[Means for solving problems]

In order to solve the above problems, the equilibrium moisture measuring device according to the present invention includes a lever that is displaced depending on the weight of the sample, a displacement sensor that detects the displacement of the lever, and a lever that is adjusted according to the output of the displacement sensor. and a coil through which a current is passed that generates a magnetic force that makes the displacement of The device is housed in an airtight container, characterized in that at least an inner wall surface of the airtight container and an electric wire interconnecting the displacement sensor and the coil with an external circuit are coated with a hydrophobic fluororesin. do. [Function] At least the inner wall surface of the container and the electric wire, which account for most of the contribution of water adsorption to the total amount, are made hydrophobic.
In other words, since it is coated with a fluororesin that absorbs almost no moisture at the molecular level, equilibrium can be achieved in a short time, making it possible to measure the equilibrium moisture content of a sample in a short time. [Example] Hereinafter, an example of the equilibrium moisture measuring device according to the present invention will be described based on the drawings. In FIG. 1, an equilibrium moisture measuring device 1 has a vacuum container 10 and a gas adsorption chamber 11 communicated with the vacuum container 10 for adsorbing and desorbing water vapor to a sample, and these are made of stainless steel. Its inner wall surface is coated with trifluorochloroethylene resin, which is a hydrophobic fluororesin, without pinholes. The coating thickness is preferably between 10 .mu.m and 1000 .mu.m, preferably between 100 .mu.m and 500 .mu.m. An electronic weighing container 14 is housed in the vacuum container 10 in order to measure the weight of a sample container 13 suspended within the gas adsorption chamber 11 via a hanging core 12.
The signal from the electronic measuring device 14 is sent to the calculation/recording device 1.
5 is input. The sample container 13 is for accommodating a sample S made of dried tobacco leaves, for example, and is made of quartz. Further, a pressure sensor 16 is provided on the inner wall of the vacuum vessel 10 as a pressure measuring means for measuring the pressure inside the vacuum vessel 10 and the gas adsorption chamber 11, and the signal from the pressure sensor is sent via the amplifier 17 to the above-mentioned calculation and calculation method. It is input to the recording device 15. on the other hand,
A temperature sensor 18 as a temperature measuring means for measuring the temperature inside the gas adsorption chamber 11 is provided on the inner wall of the gas adsorption chamber 11. The generated signal is sent to the calculation/recording device 1 via the amplifier 19.
5 is input. With the above, calculation/recording device 1
5 calculates and records the equilibrium moisture content based on the signals from the electronic measuring device 14, the pressure sensor 16, and the temperature sensor 18. The vacuum container 10 has a constant temperature liquid inlet 20 at the bottom.
a, the vacuum container 10 is surrounded by a vacuum container storage case 20 having a constant temperature liquid discharge port 20b at the top;
A constant temperature liquid flow path is formed between the vacuum container storage case 20 and the vacuum container storage case 20. On the other hand, the gas adsorption chamber 11 has a constant temperature liquid inlet 21a at the bottom and a constant temperature liquid outlet 2 at the top.
1b, and forms a constant temperature liquid flow path between the gas adsorption chamber 11 and the outer tube 21. The equilibrium moisture measuring device 1 also includes the vacuum container 10
It has a liquid reservoir 22 that accommodates distilled water A, which is the source of water vapor introduced into the tank. The station reservoir 22 is connected to a gas reservoir 23 that accommodates water vapor via pipes P1 and P2. A solenoid valve G is installed between pipes P1 and P2.
1 is provided, and a liquid reservoir 2 is opened and closed by opening and closing the solenoid valve G1.
The supply of the steam generated in step 2 to the gas reservoir 23 is controlled. The gas reservoir 23 is connected to the vacuum vessel 10 via a branch line P3 and a solenoid valve G2, and to a trap 24 via a branch line P3, a solenoid valve G3, and lines P4 and P5. The trap 24 and the oil rotary pump 25 constitute the vacuum exhaust system 2. The pressure sensor 1 is connected to the pipe P5.
Mercury manometer 26 used for calibration of 6
are connected via a pipe P6. The liquid reservoir 22, gas reservoir 23, and branch pipe P3 are surrounded by outer tubes 27, 28, and 29, respectively. The outer tubes 27, 28, and 29 have constant-temperature liquid inlets 27a, 28a, and 29a at their lower portions or bottoms, and constant-temperature liquid discharge ports 27b, 28 at the top.
b and 29b, respectively, and have outer pipes 27, 28, and 29, a liquid reservoir 22, a gas reservoir 23, and a branch pipe P3.
A constant temperature liquid flow path is formed between the two. A constant-temperature liquid at a predetermined temperature to be supplied to the constant-temperature liquid flow path is produced in a constant-temperature bath 30, and introduced into and discharged from each flow path by a circulation pump 31 to be circulated. The outer tubes 21, 27, 28, and 29 are made of special heat-resistant transparent glass to have a double tube structure, and in particular, the outer tubes 27, 28, and 29 are fixed to the frame 32 with support fittings _K1 to _K4 . has been done. In addition, the pedestal 32
is made portable by casters C1 and C2. As shown in FIG. 2, the electronic measuring instrument 14 has the following features:
It has a lever 14b that is swingably supported about a fulcrum 14a, and the above-mentioned sample container 13 is connected to one end of the lever 14b via a hanging core 12. The other end of the lever 14b faces the displacement sensor 14c, and a force coil 14d is attached to an intermediate portion between the other end of the lever 14b and the fulcrum 14a. The force coil 14d is the magnet 14e.
and the yoke 14f.
Mg is allowed to move freely. The force coil 14d has a structure in which insulated copper wire is wound in multiple layers on a bobbin. The insulation coating of the copper wire is applied by extruding heat-molten hydrophobic fluorocarbon resin, tetrafluoroethylene resin, and inserting the copper wire into it to form a coating without pinholes. The surface of the coil formed by winding the copper wire around a bobbin is further coated with trifluorochloroethylene resin, which is a hydrophobic fluororesin. The coating thickness of the copper wire is preferably 10 μm to 1000 μm, particularly preferably 100 μm to 300 μm.
The trifluorochloride ethylene resin coated on the coil is used to eliminate gaps between the copper wires wound around the bobbin, and must be coated by vacuum impregnation. This trifluorochloroethylene coating must also have no pinholes, and its wall thickness must be sufficient to eliminate gaps between copper wires, preferably between 10 μm and 1000 μm, especially 100 μm. ~500 μm is best. Incidentally, the heat resistance temperature of the above-mentioned tetrafluoroethylene coated wire is higher than the firing temperature of the trifluorochloroethylene resin. When applying the coating,
Instead of directly vacuum-impregnating a coil made using enamel-coated copper wire with trifluorochloroethylene resin, a coil made using tetrafluoroethylene-coated wire is vacuum-impregnated with trifluoroethylene resin. The reason for this is actually here. In other words, if a coil made using enamel-coated copper wire is vacuum-impregnated directly with trifluorochloroethylene resin, the firing temperature of the trifluoroethylene resin will be higher than the heat resistance temperature of the enamel, and the enamel coating will melt. This is because insulation will be hindered. Furthermore, for the same reason, it is necessary to use a bobbin made of a material having a heat resistance higher than the firing temperature of the trifluorochloroethylene resin, such as alumina. In addition, as a measure to prevent water adsorption to the coil, we have shown an example in which a coil made using tetrafluoroethylene-coated wire is coated with trifluorochloroethylene resin. Just making a coil can significantly prevent moisture adsorption. The displacement sensor 14c is a lever 14 depending on the load.
Detect the displacement of b and send the displacement signal to the insulated wire L ₁
The measurement circuit 1 provided outside the case 20 by
Enter in 4g. The measurement circuit 14g connects the force coil 14 through the insulated wires _L2 and _L3 so that the displacement becomes zero according to the signal from the displacement sensor 14c.
Control the current flowing through d, read the current value,
The weight of the sample S is measured, and the measurement result is output to the calculation/recording device 15. The coating of the above-mentioned insulated wires L ₁ to _{L 3} is formed by a pinhole-free coating using tetrafluoroethylene resin, which is a hydrophobic fluororesin, similarly to the force coil 14d, and the coating thickness is 10 μm.
The range is preferably between m and 1000μm, especially between 100μm and 300μm.
m is the best. The measurement circuit 14g is configured as shown in FIG. 3, and the displacement signal from the displacement sensor 14c is transmitted through a preamplifier 141, a PID control section 142, and a power amplifier 143 to a force coil 14d placed in the magnetic field of the magnetic gap Mg. A current is applied and the displacement is automatically returned to zero. At this time, force coil 14d
The current flowing through the is exactly proportional to the weight that is the source of the displacement, passes through the range switching section 144, enters the AD converter 145, and after being digitized, the microcomputer 1
At 46, various calculations and other operations are performed according to commands from the control switch 147, and outputted from an output terminal 148 to the calculation/recording device 15. The calculation/recording device 15 performs calculations according to the above equations (1) and (2) using the weight signal from the measurement circuit 14g, the pressure signal from the pressure sensor 16, and the temperature signal from the temperature sensor 18, and records the results using, for example, a printer. do. Equilibrium moisture is measured using the equilibrium moisture measuring device 1 configured as described above in the following manner. First, distilled water A is stored in the liquid reservoir 22, and the solenoid valve G
1. With G3 open and G2 closed, operate the vacuum exhaust system 2 to reduce the pressure in the liquid reservoir 22 and remove the air dissolved in the distilled water A, then open the solenoid valves G1 and G3.
Close. Next, the sample container 1 in the gas adsorption chamber 11
3 is filled with the sample S, the solenoid valves G2 and G3 are opened and the vacuum evacuation system 2 is operated to maintain the inside of the apparatus at approximately 10 ^-3 mmHg, and the circulation pump 3 is
1, a constant temperature liquid having a temperature of 80° C. to 100° C. is circulated around the outer circumference of the gas adsorption chamber 11 from the constant temperature bath 30 to dry the sample S for 8 hours to 12 hours. When the weight of the sample S ceases to fluctuate and becomes constant, the dry weight of the sample S is determined by the electronic weighing device 14. Next, after adjusting the temperature of the constant temperature liquid to the measurement temperature,
While maintaining the inside of the device under reduced pressure of 10 ^-3 mmHg, close solenoid valves G2 and G3, open solenoid valve G1 to introduce water vapor from liquid reservoir 22 to gas reservoir 23, and close solenoid valve G1. . Then, the solenoid valve G2 is opened to release the water vapor into the vacuum container 10 and the gas adsorption chamber 11.
The pressure is measured by the pressure sensor 16. If the pressure within the adsorption chamber 11 does not reach the measured pressure, the vacuum vessel 10 and the gas adsorption chamber 11 are set to the measured pressure by repeating the above procedure. When equilibrium is reached, the vacuum vessel 10 and gas adsorption chamber 1
Since the pressure inside 1 and the weight of the sample are constant,
A pressure sensor 16 measures the pressure inside the vacuum container 11 at that time.
At the same time, the weight of the sample S is measured using the electronic calculator 14. Operate as above to change the pressure of water vapor,
Alternatively, the equilibrium moisture content of the sample S can be measured by changing the measurement temperature. In the equilibrium moisture measuring device 1 having the configuration described above, the gas adsorption chamber 11 is not filled with the sample S.
The temperature inside the gas adsorption chamber 11 and the vacuum container 10 were set to approximately 50°C, and the initial water vapor pressure within the gas adsorption chamber 11 and the vacuum vessel 10 was set to 73 mmHg.
In order to compare with the case where the measures to prevent moisture adsorption are not stopped, the change in water vapor pressure within the vacuum container 11 over time was measured using the pressure sensor 16, and results as shown by curve B in FIG. 4 were obtained. As can be seen from curve B in FIG. 4, it was confirmed that by taking measures to prevent water adsorption, the water vapor pressure could be maintained at a constant value without using sample S. Also,
Using Burley tobacco shreds as sample S, after measuring the dry weight, the temperature in the gas adsorption chamber 11 was set to 50°C.
℃, the initial water vapor pressure in the gas adsorption chamber 11 and the vacuum vessel 10 was set to 73 mmHg, and in order to compare with the case where no measures were taken to prevent moisture adsorption, the vacuum vessel 1
When the pressure sensor 10 measured the change over time in the water vapor pressure within 0, the results shown by curve B in FIG. 5 were obtained. As can be seen from curve B in Figure 5, by taking measures to prevent moisture adsorption,
It was confirmed that even when Burley tobacco shreds were used for Sample S, the value reached a constant value in a relatively short time compared to when no measures were taken to prevent moisture adsorption. In the above-described embodiment, the magnetic field of the magnetic gap Mg in which the force coil 14d of the electronic measuring instrument 14 is accommodated is formed by the magnet 14e, but in rare cases, this magnetic field may be formed by an electromagnet. In such a case, a coil that is much larger than the force coil 14d forming the electromagnet will be housed in the vacuum container 10, and the moisture adsorption amount contribution rate will change greatly. In such an example, if measures are not taken to prevent water adhesion, the inside of the gas adsorption chamber 11 and the vacuum container 10 in the apparatus shown in FIG ^.
After setting the temperature to mmHg, the gas adsorption chamber 11 and the vacuum container 10
Water vapor is adsorbed inside. Therefore, the temperature inside the gas adsorption chamber 11 and the vacuum vessel 10 was set to 50°C, and the initial water vapor pressure was set to 73 mmHg, and the amount of water adsorption of each of the parts inside the gas adsorption chamber 11 and the vacuum vessel 10 was measured. When we calculated the contribution rate, we obtained the results shown in the table below.

〔effect〕

As explained above, according to the present invention, at least the inner wall surface of the airtight container accommodating the measuring means, the displacement sensor of the measuring means, the electric wire interconnecting the coil, and the external circuit are coated with hydrophobic fluororesin. By using simple means, the amount of moisture adsorbed within the airtight container is significantly reduced and an equilibrium state can be achieved in a short time, making it possible to obtain equilibrium moisture in a short time and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing the overall configuration of an embodiment of the equilibrium moisture measuring device according to the present invention, and FIG.
The figure is an enlarged detailed view of a part of Figure 1, Figure 3 is a block diagram showing a specific example of the circuit in Figure 2, and Figures 4 and 5 compare the effects of the present invention with the conventional example. This is a graph showing. 10... Vacuum container, 11... Gas adsorption chamber, 14
...Electronic measuring instrument, 14c...Displacement sensor, 14d
...Force coil, 14g...External circuit, S...
...Sample, _L1 to _L3 ...Electric wire.

Claims (1)

[Scope of Claims] 1. A lever that is displaced by the weight of a sample, a displacement sensor that detects the displacement of the lever, and a current that generates a magnetic force that makes the displacement of the lever zero according to the output of the displacement sensor. An equilibrium moisture measuring device comprising: a coil through which current is passed; and a weighing means for measuring the weight of the sample by the current flowing through the coil, housed in an airtight container in which internal temperature and water vapor pressure can be set. An equilibrium moisture measuring device characterized in that at least an inner wall surface of the airtight container and an electric wire interconnecting the displacement sensor and the coil with an external circuit are coated with a hydrophobic fluorine resin.