Moisture meter and method for controlling the moisture meter

Abstract

The object of the present invention is to provide a heat-drying moisture meter that can easily set the optimum heating temperature for samples with low moisture content. [Solution] The moisture meter (100) comprises a mass sensor (2), a heating unit (3), and an arithmetic and control unit (5), wherein the arithmetic and control unit (5) heats a preliminary test sample for a predetermined time at each temperature step while sequentially increasing the heating temperature, records the state of the preliminary test sample at each temperature step, and has a heating temperature determination unit (52) that executes a heating temperature determination mode in which, when a change in the state of the preliminary test sample is recorded, the temperature of the previous step is set as the set heating temperature of the measurement sample, and the preliminary test sample is of the same material as the measurement sample.

Description

[Technical Field]

[0001] The present invention relates to a moisture meter, and more particularly to a heat-drying moisture meter and a control method thereof. [Background technology]

[0002] A heat-drying moisture meter is known as one type of device for measuring the moisture content of a sample. A heat-drying moisture meter evaporates the moisture in a sample by heating it, and when the mass change (decrease) of the sample becomes constant, it is determined to be sufficiently dry and the heating is stopped. The moisture content of the sample is measured from the change in mass of the sample before and after heat-drying. The moisture content M [%] can be calculated using equation (1). M[%]=(W0-D) / W0*100 (1) (Where, W0 is the sample mass before heating and drying, and D is the sample mass after heating and drying.)

[0003] Some substances in samples undergo changes in state, such as melting or burning, when heated, and these changes in state can hinder accurate moisture content measurement. For this reason, it is important to set the heating conditions, especially the heating temperature, appropriately.

[0004] Patent Document 1 discloses a heating and drying type moisture meter that is configured to increase the heating temperature in stages to heat a preliminary test sample and detect changes in moisture content, calculate a parameter of a time function indicating changes in moisture content based on the detected changes in moisture content, and select a temperature suitable for heating the sample, assuming that drying is complete when the parameter changes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-286609 [Patent Document 2] Japanese Patent Application Publication No. 2023-133689 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the moisture meter of Patent Document 1 has a problem in that, in the case of a sample with a low moisture content such as a resin pellet, the change in moisture content due to heating is small, and the change in parameters cannot be accurately determined.

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide a heat-drying type moisture meter that can easily set the optimum heating temperature for a sample with a low moisture content. [Means for solving the problem]

[0008] In order to achieve the above object, a moisture meter according to one aspect of the present invention has the following configuration.

[0009] 1. A moisture meter comprising a mass sensor that measures the mass of a sample placed on a sample tray, a heating unit that heats the sample, and an arithmetic and control unit that controls the heating unit to heat the sample at a set temperature and calculates the moisture content of the sample from the difference in the mass of the sample before and after heating, wherein the arithmetic and control unit is further provided with a heating temperature determination unit that executes a heating temperature determination mode in which the heating temperature is increased in stages, heating a preliminary test sample for a predetermined time at each temperature stage, recording the state of the preliminary test sample at each temperature stage, and, if a change in the state of the preliminary test sample is recorded, setting the temperature of the previous stage as the set heating temperature for the measurement sample, and wherein the preliminary test sample is made of the same material as the measurement sample.

[0010] 2. In the above aspect 1, the apparatus further comprises an openable heater cover that forms a heating chamber by placing the sample dish inside and covering the sample dish, an output unit that outputs information to a user, and an input unit that inputs information from the user, and at the end of each temperature step, the apparatus further comprises an openable heater cover that forms a heating chamber by placing the sample dish inside and covering the sample dish, an output unit that outputs information to a user, and an input unit that inputs information from the user, and - It is also preferable to open the tar cover, have the user check the state of the preliminary test sample, and have the user input the state through the input unit, thereby recording the state.

[0011] 3. In the above aspects 1 and 2, it is also preferable that the measurement sample is a resin pellet.

[0012] 4. In the above aspects 1 to 3, it is also preferable that the heating temperature determination unit sets heating conditions that narrow the interval between the temperature step at which the state of the preliminary test sample changed and the temperature of the temperature step immediately before that, and executes the heating temperature determination mode again using those heating conditions.

[0013] 5. In the above aspects 1 to 4, it is also preferable that the heating temperature determination unit sets a target value for the moisture content of the measurement sample, heats the preliminary test sample at the set heating temperature for a predetermined time while monitoring the moisture content of the sample, and includes an end time determination unit that sets the time at which the moisture content reaches the target value as the measurement heating time for measurement.

[0014] 6. The above 1 of In one aspect, it is also preferable that the system further includes a camera that takes images of the preliminary test sample at predetermined intervals during measurement, and that the heating temperature determination unit determines the state of the preliminary test sample based on the images and sets the temperature at the stage just before the temperature at which the state of the preliminary test sample changes as the heating temperature of the sample.

[0015] A method for controlling a moisture meter according to another aspect of the present invention has the following configuration. 7. A control method for a moisture meter, which is executed by an arithmetic control unit of the moisture meter, in which the moisture content of the sample is calculated from the difference in mass of the sample before and after heating and the sample is heated at a set temperature, the heating temperature is increased stepwise, and a preliminary test sample is heated for a predetermined time at each temperature step, the state of the preliminary test sample is recorded at each temperature step, and when a change in the state of the preliminary test sample is recorded, the temperature at the previous step is set as the heating temperature of the measurement sample, and the preliminary test sample is made of the same material as the measurement sample.

[0016] Furthermore, a program according to another aspect of the present invention has the following configuration. 8. The computer that is the calculation control unit of the moisture meter in 7 above is executed. [Effects of the Invention]

[0017] According to the above aspect, it is possible to provide a heating and drying type moisture meter that can easily set the optimum heating temperature for a sample with a low moisture content. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing the configuration of a moisture meter according to a first embodiment. [Figure 2] FIG. 2 is a perspective view showing the moisture meter with the heater cover open. [Figure 3] 10 is a flowchart showing the process of a heating temperature determination mode in the moisture meter. [Figure 4] FIG. 10 is a diagram showing an example of a message that prompts the user to record the state of the sample, which is displayed in the heating temperature determination mode. [Figure 5] FIG. 10 is a diagram showing an example of a measurement result screen displayed in the heating temperature determination mode. [Figure 6] Photographs (A) to (D) show the state of the preliminary test sample when heated in the heating temperature setting mode. [Figure 7] FIG. 10 is a diagram showing an example of a heating temperature determination screen displayed in the heating temperature determination mode. [Figure 8] 10 is a flowchart illustrating a modified example of the processing in the heating temperature determination mode. [Figure 9] FIG. 10 is a configuration block diagram of a moisture meter according to another modified example of the moisture meter. [Figure 10] 10 is a flowchart showing a process in a heating temperature determination mode in the moisture meter. [Figure 11] FIG. 10 is a block diagram showing the configuration of a moisture meter according to a second embodiment. [Figure 12]10 is a flowchart showing an example of processing in a heating end time determination mode in the moisture meter. [Figure 13] (A) is the moisture content-time profile when the heating end time determination mode is executed, and (B) is the moisture content-time profile of multiple measurements using the determined measurement heating time. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. In this specification, unless otherwise specified, the term "moisture meter" refers to a heat-drying moisture meter. In the following description of the embodiments, unless otherwise specified, components having the same mechanical configuration are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate.

[0020] 1. First embodiment Fig. 1 is a block diagram showing the configuration of a moisture meter 100 according to a first embodiment, and Fig. 2 is a perspective view showing the moisture meter 100 with the lid 9 open. As shown in Fig. 1, the moisture meter 100 includes a sample dish 2a, a mass sensor 2, a heating unit 3, an open / close sensor 4, a calculation control unit 5, an input unit 6, a display unit 7, a memory unit 8, and a timer 12.

[0021] 2, moisture meter 100 externally comprises housing 10, sample dish 2a, and lid 9. Housing 10 houses mass sensor 2, calculation control unit 5, and memory unit 8, and sample dish 2a is placed on the top surface of housing 10. Lid 9 has a container shape that covers sample dish 2a and can be opened and closed by rotating around rotation axis 9b located behind sample dish 2a, as shown by arrow A.

[0022] A rectangular container-shaped heater cover 9a, which is slightly smaller than the lid 9 and covers the sample dish 2a, is attached to the lid 9. As a result, the heater cover 9a can be opened and closed together with the lid 9. The heating unit 3 is disposed between the heater cover 9a and the lid 9. The heater cover 9a is made of a transparent resin plate, and when closed, it defines a heating chamber together with the top surface of the housing 10.

[0023] Mass sensor 2 is an electronic sensor of the electromagnetic balance type, strain gauge type (load cell type), or capacitance type. Mass sensor 2 is housed in housing 10 and connected to sample tray 2a via a connecting shaft (not shown). Mass sensor 2 detects the mass of a sample placed on sample tray 2a. Mass sensor 2 is connected to calculation control unit 5 via an A / D converter (not shown), and constantly outputs a mass detection signal to calculation control unit 5.

[0024] The sample dish 2a is placed in the heating chamber. The sample dish 2a has a handle 2b and is configured to be detachable from the mass sensor 2. The lid 9 is provided with an opening / closing sensor 4 that detects whether the heater cover 9a is open or closed. The opening / closing sensor 4 may be, for example, a microswitch such as a limit switch. The opening / closing sensor 4 is connected to the calculation control unit and outputs a detection signal to the calculation control unit 5.

[0025] The heating unit 3 is equipped with heating means 3a, such as a halogen lamp or a resistance wire that generates Joule heat, and a temperature sensor 3b. The heating means 3a is controlled by the calculation control unit 5 based on the output from the temperature sensor 3b, and heats the heating chamber (sample) to a set temperature.

[0026] The input unit 6 is configured as, for example, a touch panel display, integral with the display unit 7. The input unit 6 accepts instructions and information input from the user to the calculation control unit 5. The input unit 6 also includes a power button, a measurement stop button, etc.

[0027] The display unit 7 is, for example, a liquid crystal display, and displays a screen for outputting information such as measurement results to the user, and a screen for inputting instructions from the user.

[0028] The arithmetic control unit 5 is embodied by a microcomputer in which a CPU (Central Processing Unit) for performing arithmetic processing, and a ROM (Read Only Memory) and RAM (Random Access Memory) as auxiliary storage units are implemented in an integrated circuit.

[0029] The calculation control unit 5 includes, as functional units, a sample measurement unit 51 and a heating temperature determination unit 52. Each functional unit is configured with electronic circuits such as a CPU, an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array), etc. Furthermore, when configured with a CPU, the function of the functional unit is realized by reading from a storage unit and executing a program for executing the function of the functional unit.

[0030] The sample measurement unit 51 executes a sample measurement mode, which is commonly used to measure the moisture content of a sample. Specifically, the sample measurement unit 51 controls the heating unit 3 to heat the sample at a set heating temperature, monitoring the sample mass and the change in sample mass. When the sample mass change rate falls below a predetermined threshold, the heating unit 3 stops and the moisture content of the measured sample is calculated. Alternatively, when a preset measurement heating time has elapsed, the unit 51 receives an end signal from the timer 12, stops the heating unit 3, and calculates the moisture content of the measured sample. For resin pellets with a low moisture content, the measurement is generally terminated by a timer.

[0031] Furthermore, the sample measurement unit 51 calculates the moisture content M of the measurement sample using the mass measurement value of the sample before heating and the mass measurement value after heating according to the following formula (2). M(%)=[[(W1-W2)] / W1]×100 ···(2) (W1 is the mass measured before heating, and W2 is the mass measured after heating.)

[0032] The heating temperature determination unit 52 executes a heating temperature determination mode that determines the heating temperature when heating the measurement sample in the sample measurement mode. Specifically, the heating temperature determination unit 52 controls the heating unit 3 to gradually increase the heating temperature, heating a preliminary test sample made of the same material as the measurement sample for a predetermined time at each temperature step. During this heating, the moisture content is monitored. The moisture content change over time (% / min) obtained by differentiating the moisture content may also be monitored. While monitoring the moisture content change over time is not essential in this mode, it is performed to determine the dryness state of the sample.

[0033] Table 1 shows an example of heating conditions in the heating temperature determination mode. Under the conditions in Table 1, the heating temperature is 100°C from 0 to 5 minutes after the start of heating, 120°C from 5 to 10 minutes, 140°C from 10 to 15 minutes, and so on, with the temperature increasing in steps at 20°C intervals, with heating lasting 5 minutes at each temperature step. The heating temperature and heating time at each step can be set appropriately depending on the sample to be measured.

[0034] [Table 1]

[0035] The heating conditions in the heating temperature setting mode are stored in advance in the storage unit 8. A plurality of heating conditions may be stored in the storage unit 8 according to the type of measurement sample, and the user may be able to select and set one of these. Alternatively, the user may be able to set the conditions by individually inputting them.

[0036] Next, the heating temperature determination unit 52 records the state of the preliminary test sample at each temperature step. If a change in the state (appearance) of the preliminary test sample is recorded, the temperature at the previous step is set as the heating temperature in the sample measurement mode. If the measurement sample is a resin pellet, heating it above its glass transition point or melting point can cause its appearance to change, such as a translucent material becoming transparent or a transparent material becoming cloudy. For example, polypropylene resin pellets are milky white (see, for example, Figure 6(A) described below), but as the heating temperature is increased, the pellets melt and become transparent (see, for example, Figure 6(D)).

[0037] In addition, the sample may burn and change color. In this embodiment, the change in state refers to such a change in appearance. When such a change occurs, substances other than water evaporate from the sample, making it impossible to accurately measure the moisture content. In this embodiment, the heating temperature is set to the temperature just before the temperature at which such a change occurs, so that measurements can be made at a temperature that does not cause such a change.

[0038] The storage unit 8 is embodied by a non-transitory computer-readable storage medium such as a HDD, an SDD, a flash memory, etc. The storage unit 8 stores various programs that allow the arithmetic and control unit 5 to execute the functions of the functional units.

[0039] The timer 12 measures the time from the start of heating, and outputs an end signal to the calculation control unit 5 when a predetermined time set by the calculation control unit 5 has elapsed.

[0040] Next, the heating temperature determination mode will be described. (heating temperature determination mode) 3 is a flowchart of the operation of moisture meter 100 in the heating temperature determination mode. The heating temperature setting mode is executed prior to execution of the sample measurement mode, and determines the heating temperature conditions for the sample measurement mode. The heating temperature setting mode is started, for example, when the user selects the heating temperature determination mode from the mode selection screen displayed on display unit 7. During execution of the heating temperature determination mode, heating temperature determination unit 52 constantly calculates the mass based on the detection signal from mass sensor 2.

[0041] When the process starts, in step S01, the heating temperature determination unit 52 determines whether a sample has been set. When the user sets the preliminary test sample placed on the sample tray 2a on the tray holder, the heating temperature determination unit 52 determines that the sample has been set (Yes) from the detection signal of the mass sensor, and in step S02, sets the temperature stage N to N=1.

[0042] Next, in step S03, the heating temperature determination unit 52 displays a message on the display unit prompting the user to close the heater cover. In response, the user closes the heater cover 9a, and in step S04, when the heating temperature determination unit 52 detects that the heater cover 9a has been closed based on the detection signal from the open / close sensor 4 (Yes), the process proceeds to step S05 and heating begins at the temperature of temperature stage 1 of the heating temperature conditions. Once heating begins, the heating temperature determination unit 52 constantly monitors the moisture content based on the signal from the mass sensor 2. The amount of change in the moisture content is also calculated and monitored in the same manner.

[0043] Then, in step S06, when the set predetermined time has elapsed (Yes), in step S07, heating temperature determination unit 52 stops heating unit 3 to interrupt heating.

[0044] Next, in step S08, the heating temperature determination unit 52 displays a message on the display unit 7 urging the user to open the heater cover 9a. In response, the user opens the heater cover 9a, and in step S09, when the heating temperature determination unit 52 detects that the heater cover 9a has been opened based on the detection signal from the open / close sensor 4 (Yes), the process proceeds to step S10, where the display unit 7 displays a message urging the user to check the sample state. The user checks the sample state in response to this message.

[0045] Next, in step S11, the heating temperature determination unit 52 displays options based on whether or not there has been a change in the state of the preliminary test sample. Figure 4 shows an example of a screen on the display unit 7 that simultaneously displays the message of step S10 and options based on whether or not there has been a change in state. The user touches and selects the option that matches the confirmed state of the sample.

[0046] If "No change" is selected in step S12, the heating temperature determination unit 52 proceeds to step S13 and determines whether the current temperature stage is the final temperature stage. If it is not the final stage (No), the process proceeds to step S14, where the temperature stage N is set to N=N+1, and the process returns to step S03. If it is the final stage in step S13 (Yes), the process proceeds to step S15, where the heating temperature of the final stage is determined as the optimal heating temperature, displayed on the display unit 7, and determined as the heating temperature for the next sample measurement mode, and the process ends.

[0047] On the other hand, if "No change" is not selected in step S12, heating temperature determination unit 52 determines whether "Changed" is selected in step S16. If "Changed" is selected, heating temperature determination unit 52 determines whether the current temperature stage is the first temperature stage (temperature stage 1) in step S17.

[0048] If in step S17 it is not the first temperature stage, i.e., it is temperature stage 2 or later (No), in step S18 the temperature of the previous stage is determined to be the optimal heating temperature for measuring the same measurement sample as the preliminary test sample, and this is displayed on the display unit 7, and the heating temperature for the sample measurement mode to be performed next is determined, and the process is terminated.

[0049] On the other hand, if the current temperature stage is the first temperature stage (temperature stage 1) in step S17 (Yes), the heating temperature determination unit 52 determines in step S19 that there is no optimal heating temperature for measuring the measurement sample, displays a message on the display unit 7 indicating that the determination of the heating temperature has failed, and terminates the processing.

[0050] Fig. 5 shows an example of the display on the display unit 7 when the measurement is completed, and shows the display when proceeding to step S18. Figs. 6(A) to 6(C) show an example of the state of the sample corresponding to the measurement in Fig. 5. Fig. 6(D) shows, for reference, the same resin pellets as in Figs. 6(A) to 6(C) completely melted after heating at 180°C for 5 minutes. The resin pellets are polypropylene.

[0051] As shown in Figure 5, the display unit 7 displays the results by plotting the moisture content vs. time profile, as well as displaying the moisture content at the end of each temperature step, the amount of change in moisture content, and the results of the sample condition in a table. This type of display allows the user to easily grasp the overall picture of the measurement results.

[0052] The results in Figure 5 show that no change in state occurred at temperature stage 1 (100°C) or temperature stage 2 (120°C). In fact, as shown in Figure 6(B), there was no change in state between the end of temperature stage 2 and the state before heating shown in Figure 6(A). It was determined that the state of the sample changed at temperature stage 3 (140°C). In fact, Figure 6(C) shows that the resin pellets began to melt, with some areas becoming transparent. Thus, the moisture meter 100 records the user's assessment of the visual changes in the resin pellets at each stage and terminates the measurement if a change is determined. In this case, 120°C, the previous stage (temperature stage 2), is determined to be the optimal heating temperature. Figure 7 shows an example of a heating temperature determination screen displayed on the display unit 7.

[0053] The heating temperature determined in this manner may be selected by the user as the optimum heating temperature at the start of the sample measurement mode. Alternatively, it may be automatically set as the heating temperature in the sample measurement mode. This process may be performed in steps S15 and S18, or may be performed while the sample measurement mode is running.

[0054] Note that, although the display unit 7 in the present embodiment corresponds to the output unit in the claims, the output unit is not limited to the display unit 7. For example, the moisture meter 100 may further include an audio output unit that notifies the user of information by audio messages, and the audio output unit may notify the messages in steps S03, S08, and S10 in addition to or instead of displaying them on the display unit 7. Alternatively, these messages may be displayed not only on the display unit 7 but also on the display unit of an external device, such as a computer or smartphone, connected via the communication unit, if a communication unit is further provided.

[0055] (Action and effect) The moisture meter 100 according to this embodiment is configured to increase the temperature stepwise and record the state of the preliminary test sample at each temperature step. As a result, it is possible to identify the temperature at which the state of the sample changes with a single measurement. Furthermore, by determining the temperature at the temperature step before the state of the preliminary test sample changes as the heating temperature in the sample measurement mode, it is possible to easily determine an appropriate heating temperature that will not melt or burn the measurement sample during measurement. This moisture meter 100 and method are particularly suitable for use with samples with low moisture content, such as resin pellets.

[0056] In the moisture meter 100 of the embodiment that normally includes a heater cover 9a, the condition of the sample cannot be visually confirmed when the heater cover 9a is closed. Furthermore, in a typical moisture meter, if the heater cover 9a is opened during measurement, the measurement ends with an error. In this embodiment, the user is configured to be able to check the condition of the sample between each temperature step, and the user is notified of this via the output unit. As a result, the user can determine the appropriate heating temperature simply by following the instructions of the moisture meter 100 to determine the condition of the sample and inputting the determination result into the moisture meter 100, thereby reducing the burden on the user.

[0057] (Variation 1) The following modifications may be made to moisture meter 100 according to the present embodiment: Fig. 8 is a flowchart illustrating one modification of the processing in the heating temperature determination mode of moisture meter 100.

[0058] This modification is a modification of the embodiment in which a change in state occurs and the temperature at the stage immediately preceding the temperature stage at which the change occurred is determined as the heating temperature. Therefore, after step S18 described in FIG. 3, the additional step of FIG. 8 is executed.

[0059] Specifically, when the temperature of the immediately preceding temperature step is determined as the heating temperature in step S18, in step S21 the heating temperature determination unit 52 divides the temperature between the temperature of the immediately preceding temperature step and the temperature of the temperature step that has changed into finer steps, and calculates new heating conditions.

[0060] For example, as in the above example, if the state change is temperature stage 3 (140°C) and the heating temperature is determined to be temperature stage 2, 120°C, updated heating conditions are calculated with 5°C intervals between 120°C and 140°C. That is, the updated heating conditions are as follows: temperature stage 1 is 120°C, temperature stage 2 is 125°C, temperature stage 3 is 130°C, temperature stage 4 is 135°C, and temperature stage 5 is 140°C.

[0061] Next, in step S22, the heating temperature determination unit 52 displays a message on the display unit 7 urging the user to remove the measured preliminary test sample, place a new preliminary test sample, and perform the measurement again. Then, in step S23, steps S01 to S19 are repeated using the updated heating conditions, and the process ends.

[0062] In this way, the heating temperature determined is the highest temperature to which the measurement sample can be heated without melting or burning, and in this modified example, it is possible to more accurately determine the optimal heating temperature.

[0063] (Variation 2) 9 is a configuration block diagram of a moisture meter 100A according to another modification of moisture meter 100. Moisture meter 100A has roughly the same configuration as moisture meter 100. However, it differs in that it further includes camera 11, and calculation control unit 5A, which has the same mechanical configuration as calculation control unit 5, includes heating temperature determination unit 52A instead of heating temperature determination unit 52.

[0064] The camera 11 includes an imaging element such as a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor), a lens, and lighting such as an LED (Light Emitting Diode). It is installed inside the lid 9 and, when the heater cover 9a is closed, captures an image of the sample placed on the sample tray 2a and outputs the image to the calculation control unit 5A.

[0065] Heating temperature determination unit 52A executes the heating temperature determination mode in the same way as heating temperature determination unit 52. However, instead of recording changes in the state of the sample by prompting the user to confirm it, it determines the change in state based on an image of the sample acquired by camera 11, and if the state has changed, it records that fact and sets the temperature at the stage immediately before that as the heating temperature in the sample measurement mode.

[0066] The heating temperature determination unit 52A can determine whether the state of the preliminary test sample has changed by using a learning model that determines whether the state of the resin has changed, which is generated by learning a large number of images of the resin before heating and after heating in which the state has changed using, for example, a convolutional neural network (CNN). The method for generating the learning model is not limited to CNN, and support vector machines, random forests, K-nearest neighbor methods, etc. may also be used. Furthermore, a known image judgment technique that does not use a learning model may also be used to make the determination.

[0067] FIG. 10 is a flowchart illustrating an example of the processing of the heating temperature determination unit 52A in the heating temperature determination mode. Steps S31 to S37 are the same as steps S01 to S07, and therefore their description is omitted. Following step S37, in step S38, the heating temperature determination unit 52A drives the camera 11 to capture an image of the sample's state. Next, in step S39, the heating temperature determination unit 52A determines whether the state has changed. If no change has occurred, in step S40, it determines whether the current temperature stage is the final temperature stage, and in steps S41 and S42, it executes the same processes as steps S14 and S15, respectively. On the other hand, if a change has occurred in step S39, it determines whether the current temperature stage is the initial temperature stage, and in steps S44 and S45, it executes the same processes as steps S18 and S19. This configuration allows the optimal heating temperature to be automatically determined without the user having to open the heater cover 9a and visually check the state for each temperature stage. Furthermore, since heating is not stopped midway, it is possible to shorten the time required to determine the heating temperature.

[0068] In the above, the state of the preliminary test sample is determined at the end of each temperature step, but this is not limited to this. Images can also be taken at predetermined intervals during heating to determine changes in state, and when it is determined that the state has changed, the temperature of the temperature step immediately preceding that can be determined as the optimal heating temperature in the sample measurement mode.

[0069] (Second embodiment) Incidentally, standard methods for measuring moisture content include the dry weight method and the Karl Fischer method. These are considered to have higher measurement accuracy than methods using a moisture meter. For the same sample, the value obtained by a moisture meter tends to be higher than the value obtained by the standard method. For this reason, many users would like the measurement value obtained by the standard method to be the target value, and the measurement value obtained by the moisture meter to be output as a value close to the target value.

[0070] Some commercially available moisture meters are designed to multiply the measurement results by a coefficient to output a value close to the target value. However, this method has low reliability and validity. Alternatively, measurement conditions can be adjusted in various ways to output a value close to the target value, but this requires multiple measurements to determine the measurement conditions, making the process complicated.

[0071] After extensive research, the inventors discovered that if a sample is heated for a long period of time at an appropriate heating temperature using a moisture meter, the moisture content versus time profile will show a consistent curve, and that by setting the timer end time corresponding to the target value, it is possible to reproducibly output the target moisture content value.

[0072] 11 is a configuration block diagram of moisture meter 200 according to the second embodiment. Moisture meter 200 has roughly the same configuration as moisture meter 100, but includes calculation control unit 205 instead of calculation control unit 5, and calculation control unit 205 has the same mechanical configuration as calculation control unit 5, but differs in that it includes heating end time determination unit (hereinafter referred to as end time determination unit) 53 in addition to the functional units of calculation control unit 5.

[0073] The end time determination unit 53 executes an end time determination mode that determines the heating end time for outputting the moisture content at the target value. The target moisture content value is set based on user input, and the sample is heated at the set heating temperature for a predetermined time (e.g., 30 minutes) set by a timer. When heating begins, the mass is calculated sequentially, and the moisture content is calculated and monitored based on the difference between the mass during heating and the mass before heating. After the predetermined time, the heating is stopped, and the time at which the set moisture content reaches the target value is calculated from the moisture content-time profile. This time is then used as the measurement heating time. This time is then set as the heating time in sample measurement mode.

[0074] (End time determination mode) 12 is a flowchart illustrating an example of the operation of moisture meter 200 in the end time determination mode. The end time determination mode is executed after the heating temperature is determined in the heating temperature determination mode and before the sample measurement mode is executed. The end time determination mode is started, for example, when the user selects the end time determination mode from the mode selection screen displayed on display unit 7. In addition, in this end time determination mode, the optimal heating temperature determined in the heating temperature determination mode is preset.

[0075] When the process starts, in step S51, the end time determination unit 53 displays a message prompting the user to input a target value on the display unit 7. When the user inputs a target value in step S52, the end time determination unit 53 sets the target value in step S53.

[0076] Next, in step S54, after confirming that the sample has been set and the heater cover 9a has been closed, in step S55, the end time determination unit 53 controls the heating unit 3 to start heating for a predetermined time at the heating temperature determined in the heating temperature determination mode.

[0077] Next, in step S56, the mass is detected sequentially, and the moisture content is calculated based on the difference between the mass during heating and the mass before heating, and the moisture content is monitored. Then, in step S57, when a predetermined time has elapsed, in step S58, the end time determination unit 53 stops heating by the heating unit 3.

[0078] Next, in step S59, the end time determination unit 53 calculates the time at which the moisture content reaches the target value from the moisture content-time profile obtained as a result of the series of monitoring, and displays the measurement result as the measurement heating time for outputting the moisture content at the target value, and ends the process. The moisture content-time profile and the determined heating time are displayed on the measurement result display screen.

[0079] As an example, Figure 13(A) shows the moisture content vs. time profile when polyacetal resin pellets 25 are heated in timer mode for 30 minutes. The heating temperature is 130°C, which is a value determined in heating temperature determination mode. When the polyacetal resin pellets are measured using the Karl Fischer method, the moisture content is 0.087%. Therefore, the target moisture content is set to 0.087%, and the heating time (10 minutes) at which the measured moisture content is 0.087% is determined as the measurement heating time.

[0080] Figure 13(B) shows the moisture content vs. time profile obtained by running the sample measurement mode multiple times using the measurement heating time determined using the results of Figure 13(A) and the heating temperature determined in the heating temperature determination mode. Figure 13(B) shows that by using the measurement heating time and optimal heating temperature determined in this way, it is possible to output the measured moisture content as the target value with good reproducibility.

[0081] The target value set in this manner is stored in memory unit 8 together with the measurement heating time determined (estimated) by, for example, the method of Patent Document 2. By setting this as an option for the measurement heating time when executing the sample measurement mode, moisture meter 200 can output the measured value as a moisture percentage that matches the target value depending on the purpose of the measurement. Note that the target value is not limited to the moisture percentage according to the standard method described above, and a moisture percentage value that achieves the desired measurement accuracy may also be used.

[0082] The above describes preferred embodiments of the present invention, but the above embodiments are merely examples of the present invention, and these can be combined based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention.

[0083] Furthermore, although this specification refers to a heat-drying type moisture meter as the moisture meter, the present invention can also be applied to other types of moisture meters that are equipped with a mass sensor and that read the change in mass of a sample before and after heating to calculate the moisture content. [Explanation of symbols]

[0084] 1: Sample dish 2: Mass sensor 2a: Sample dish 3: Heating part 5: Calculation control unit 6: Input section 9a: Heater cover 25: Resin pellets 51: Sample measurement section 52: Heating temperature determination section 53: End time determination unit 100,200: Moisture meter 205: Calculation control unit M: Moisture percentage

Claims

1. a mass sensor that measures the mass of a sample placed on the sample tray; a heating unit that heats the sample; a calculation control unit that controls the heating unit to heat the sample at a set temperature and calculates the moisture content of the sample from the difference in mass of the sample before and after heating, The arithmetic and control unit The heating temperature is increased stepwise, and the preliminary test sample is heated for a predetermined time at each temperature step. Record the state of the preliminary test sample at each temperature step; a heating temperature determination unit that executes a heating temperature determination mode in which, when a change in the state of the preliminary test sample is recorded, the temperature at the immediately preceding stage is set as the set heating temperature of the measurement sample; The preliminary test sample is the same material as the measurement sample. A moisture meter characterized by:

2. an openable heater cover that forms a heating chamber by placing the sample dish therein and covering the sample dish; an output unit that outputs information to a user; an input unit for inputting information from a user, The moisture meter according to claim 1, wherein the output unit prompts the user to open the heater cover and check the state of the preliminary test sample at the end of each temperature step, and the user inputs the state through the input unit, thereby recording the state.

3. 3. The moisture meter according to claim 1, wherein the measurement sample is a resin pellet.

4. The heating temperature determination unit determines a temperature between the temperature stage at which the state of the preliminary test sample changes and the temperature of the temperature stage immediately before that temperature stage. Set heating conditions with narrower temperature step intervals, 3. The moisture meter according to claim 1, wherein the heating temperature determination mode is executed again using the heating conditions.

5. The heating temperature determination unit Setting a target moisture content of the measurement sample; While monitoring the moisture content of the preliminary test sample, the sample is heated at the set heating temperature for a predetermined time.

3. The moisture meter according to claim 1, further comprising an end time determination unit that sets the time at which the moisture percentage reaches the target value as a measurement heating time.

6. Further provided is a camera that takes images of the preliminary test sample at predetermined intervals during measurement; The heating temperature determination unit determining the state of the preliminary test sample based on the image; 2. The moisture meter according to claim 1, wherein the temperature immediately before the temperature at which the state of the preliminary test sample changes is set as the heating temperature of the sample.

7. A control method for a moisture meter, which causes an arithmetic control unit of the moisture meter to execute a calculation for calculating the moisture percentage of the sample from the difference in mass of the sample before and after heating, the method comprising: The heating temperature is increased stepwise, and the preliminary test sample is heated for a predetermined time at each temperature step. Record the state of the preliminary test sample at each temperature step; When a change in the state of the preliminary test sample is recorded, the temperature at the immediately preceding stage is set as the heating temperature of the measurement sample; The preliminary test sample is the same material as the measurement sample. A method for controlling a moisture meter.

8. A program for causing a computer serving as an arithmetic control unit of a moisture meter to execute the method of claim 7.

Images