Patent Description:
Conventionally, a heating and drying moisture meter is known as one of the devices that measure the moisture of a specimen (for example, Patent Literature <NUM>). The heating and drying moisture meter is a device that evaporates the moisture in a specimen by heating the specimen and measures the moisture content of the specimen from a change (decrease) in the mass of the specimen before and after heating.

The heating and drying moisture meter is a relatively inexpensive device and can measure the moisture content of a wide variety of specimens in a relatively short time. Accordingly, heating and drying moisture meters are widely used as moisture meters. In this description, a moisture meter means a heating and drying moisture meter unless otherwise specified.

Patent Literature <NUM> discloses a moisture meter configured to perform calibration by using a substance whose moisture content is known in advance, such as sodium tartrate dihydrate (C<NUM>H<NUM>Na<NUM>O<NUM>·<NUM><NUM>O, hereinafter simply referred to as "sodium tartrate"), as a standard substance for device performance inspection. Sodium tartrate is known to undergo an irreversible crystalline change to release moisture when being heated at a temperature of about <NUM> for about <NUM>.

The moisture meter disclosed in Patent Literature <NUM> compares the measured moisture content of a standard substance with the theoretical moisture content of the standard substance stored in advance in a storage unit, evaluates the comparison result based on a preset evaluation criterion, and calibrates a mass measurement unit so as to equalize the measured moisture content with the theoretical moisture content based on the evaluation result. Further background art for the present invention is described in Patent Literatures <NUM>-<NUM>.

However, the measurement performance of the moisture meter is influenced by not only the state of the mass measurement unit but also other factors especially the state of a heating unit.

In detail, when a halogen lamp as a heating means or a glass cover for protecting a specimen is contaminated or there is an abnormality such as a failure in the halogen lamp itself, the lamp cannot generate heat as expected according to its performance. Therefore, there is a problem that the measurement time may be increased.

Therefore, demands have arisen for the development of a moisture meter that can diagnose the state of a device in consideration of not only factors of a mass measurement unit but also factors other than the mass measurement unit, especially the state of a heating unit.

The present invention has been made in consideration of the above circumstances and has as its object to provide a heating and drying moisture meter that can diagnose the state of a device in consideration of not only factors of a mass measurement unit but also factors other than the mass measurement unit.

In order to achieve the above object, a moisture meter according to one aspect of the present invention includes a mass measurement unit configured to measure a mass of a specimen placed on a weighing dish, a heating chamber having the weighing dish placed inside, configured to open and close; a heating unit placed in the heating chamber and configured to heat the specimen; a control arithmetic unit configured to control the heating unit to heat the specimen until a change in mass of the specimen becomes not more than a predetermined threshold and calculate a moisture content of the specimen from the change in the mass of the specimen before and after heating, a timepiece configured to measure a heating time, and a storage unit. The control arithmetic unit includes a standard substance measurement unit configured to measure a moisture content of a standard substance for inspection as the specimen and measure a heating time and an abnormality diagnosis unit configured to diagnose presence or absence of an abnormality in the mass measurement unit by evaluating a measured moisture content with reference to a theoretical moisture content of the standard substance and to diagnose presence or absence of an abnormality in the heating unit by comparing a measured heating time with a predetermined time as a set heating time stored in the storage unit in advance.

In the above aspect, the abnormality diagnosis unit also determines that there is an abnormality in the heating unit when the measured heating time is longer than the predetermined time.

In the above aspect, the standard substance is also preferably a sodium tartrate dihydrate.

In the above aspect, the moisture meter preferably includes a display unit, and the abnormality diagnosis unit displays, on the display unit, a message notifying a user of, as diagnosis results, a location of an abnormality and a measure against a cause.

A heating and drying moisture meter can diagnose the state of a device in consideration of not only factors of a mass measurement unit but also factors other than the mass measurement unit, especially the state of a heating unit.

The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to them. In each embodiment, the same reference numerals denote the same components, and overlapping description will be omitted as appropriate.

<FIG> is a block diagram illustrating the configuration of a moisture meter <NUM> according to an embodiment of the present invention. <FIG> is a perspective view illustrating a state in which a lid <NUM> of a heating chamber C of the moisture meter <NUM> is open. As illustrated in <FIG>, the moisture meter <NUM> includes a mass measurement unit <NUM>, a heating unit <NUM>, a timepiece <NUM>, a control arithmetic unit <NUM>, an input unit <NUM>, a display unit <NUM>, and a storage unit <NUM>.

The mass measurement unit <NUM> is a so-called mass scale such as an electromagnetic balance mass sensor and is connected to a weighing dish 2a on which a specimen is placed. The mass measurement unit <NUM> measures the mass of the specimen placed on the weighing dish 2a. The mass measurement unit <NUM> is stored inside a moisture meter main body <NUM>.

The weighing dish 2a is placed in the heating chamber C sealed by closing the openable lid <NUM> illustrated in <FIG>. The weighing dish 2a includes a knob 2b and is configured to be detachable with respect to the mass measurement unit <NUM>. The heating chamber C is configured as a space defined by the upper portion of the moisture meter main body <NUM> and the lid <NUM> and houses the weighing dish 2a.

The heating unit <NUM> includes a heating means 3a such as a halogen lamp or a resistance wire that generates Joule heating and a temperature sensor (not illustrated). The heating means 3a heats a specimen under the control of the control arithmetic unit <NUM> based on an output from the temperature sensor.

The heating means 3a is stored inside the lid <NUM> of the heating chamber C. The lid <NUM> includes a glass cover 9a in the form of a container covering the weighing dish 2a to prevent a specimen from coming into contact with the heating means 3a.

The timepiece <NUM> measures the heating time from when the heating unit <NUM> starts heating under the control of the control arithmetic unit <NUM> to when the heating unit <NUM> stops heating. Note that the timepiece <NUM> may be incorporated as, for example, a system clock in the control arithmetic unit <NUM>.

The control arithmetic unit <NUM> is a microcomputer including a CPU (Central Processing Unit) that performs arithmetic processing and a ROM (Read Only Memory) and a RAM (Random Access Memory) as auxiliary storage units.

The control arithmetic unit <NUM> is connected to respective units of the mass measurement unit <NUM>, the heating unit <NUM>, the timepiece <NUM>, the input unit <NUM>, the display unit <NUM>, and the storage unit <NUM> and executes various operations for implementing the functions of the moisture meter <NUM>.

The control arithmetic unit <NUM> controls the respective units to execute measurement in the specimen measurement mode, the inspection initialization mode, and the inspection mode. The specimen measurement mode is a normal usage mode of the moisture meter <NUM>, in which the moisture meter <NUM> measures the moisture content of a specimen whose moisture content is desired to be acquired. The inspection mode is a mode of diagnosing the state of the moisture meter <NUM>. The inspection initialization mode is a mode of acquiring a default value of the heating time, that is, set heating time, for the inspection mode.

The control arithmetic unit <NUM> also includes a specimen measurement unit <NUM>, a standard substance measurement unit <NUM>, and an abnormality diagnosis unit <NUM>. Each functional unit is implemented by, for example, a program.

In the specimen measurement mode, the specimen measurement unit <NUM> controls the heating unit <NUM> to heat the specimen and monitor a change in the mass of the specimen and stops the heating unit <NUM> when the mass change rate of the specimen becomes a predetermined threshold or less.

The specimen measurement unit <NUM> calculates a moisture content M of the specimen by using the mass measurement value of the specimen before heating and the mass measurement value after heating according to equation (<NUM>). <MAT> (where W1 is the mass measurement value before heating, and W2 is the mass measurement value after heating.

In the inspection initialization mode and the inspection mode, the standard substance measurement unit <NUM> measures the moisture content of a standard substance for inspection (hereinafter simply referred to as "standard substance") like the specimen measurement unit <NUM> and measures the heating time required for measurement of the moisture content of the standard substance.

In the inspection mode, the abnormality diagnosis unit <NUM> determines whether a measured moisture content Mi of the standard substance falls within a predetermined range with reference to a theoretical moisture content Mt of the standard substance, thereby determining the presence or absence of an abnormality in the mass measurement unit <NUM>.

In the inspection mode, the abnormality diagnosis unit <NUM> determines the presence or absence of an abnormality in the heating unit <NUM> by comparing a measured heating time Ti with a set heating time Ts in the inspection initialization mode which is stored at the time of shipment.

The input unit <NUM> includes operation buttons such as a start button, a stop button, up/down buttons, a selection button, and a determination button and is used to issue instructions to start and stop measurement, set a mode, and select an operation, etc..

The display unit <NUM> is a liquid crystal display that displays measurement results, a mode selection screen, a message, etc. Note that the input unit <NUM> and the display unit <NUM> may be integrated into a touch panel display.

The storage unit <NUM> is, for example, a nonvolatile semiconductor memory such as a flash memory. The storage unit <NUM> stores a heating temperature setting and the amount of specimen placed for proper inspection in accordance with the theoretical moisture content of a standard substance and the standard substance. The storage unit <NUM> also stores the heating time for the standard substance measured in the inspection initialization mode. Furthermore, the storage unit <NUM> stores messages displayed on the display unit <NUM> by the abnormality diagnosis unit <NUM> to notify a user of diagnosis results.

Next, the standard substances used for abnormality diagnosis of the moisture meter <NUM> will be described. As standard substances, for example, the substances listed in Table <NUM> can be used, but are not limited to these substances. Sodium tartrate is especially suitable because of high stability and easy handling. With regard to these substances, appropriate heating temperatures for the measurement of theoretical moisture content and moisture content are known.

Although at least one standard substance may be set, a plurality of standard substances may also be set. In this case, the storage unit <NUM> stores the theoretical moisture content, appropriate heating temperatures, and the amounts of specimens placed of a plurality of standard substances corresponding to codes respectively assigned to the individual standard substances.

Next, the operations of the moisture meter <NUM> in the specimen measurement mode, the inspection initialization mode, and the inspection mode will be described.

<FIG> is a flowchart for the operation of the moisture meter <NUM> in a normal usage state, that is, in the specimen measurement mode of the moisture meter <NUM>.

When measuring a specimen, a user sets the moisture meter <NUM> in the specimen measurement mode via the input unit <NUM> in step S101. When the specimen measurement mode is set in advance as the normally used mode, step S101 may be omitted.

Next, in step S102, the user places the specimen on the weighing dish 2a, closes the lid <NUM>, sets a heating temperature via the input unit <NUM>, and presses the measurement start button.

Next, in step S103, the specimen measurement unit <NUM> makes the heating unit <NUM> start heating. The heating gradually evaporates the moisture of the specimen, and the mass measurement value of the specimen measured by the mass measurement unit <NUM> gradually decreases with the elapse of time.

The specimen measurement unit <NUM> monitors a change in this mass measurement value. In step S104, when the change in mass measurement value becomes not more than a predetermined threshold (Yes), the process shifts to step S105. In step S105, the specimen measurement unit <NUM> causes the heating unit <NUM> to stop heating, calculate the moisture content M according to equation (<NUM>), and stop the measurement upon displaying the calculation result on the display unit <NUM>.

<FIG> is a flowchart for explaining the operation of the moisture meter <NUM> in the inspection initialization mode. The inspection initialization mode is normally executed at the time of shipment. As a standard substance, sodium tartrate is set.

In step S201, an operator of a maker side sets the inspection initialization mode via the input unit <NUM>. In step S202, the moisture meter <NUM> measures the standard substance.

A detailed operation in measurement of the standard substance in step S202 will be described with reference to <FIG>. First, when the measurement of the standard substance starts, the standard substance measurement unit <NUM> displays, in step S301, the amount of specimen to be placed and the heating temperature setting appropriate for inspection, stored in advance in the storage unit <NUM> corresponding to sodium tartrate, on the display unit <NUM> as, for example, the following message:
"Standard Substance: Sodium tartrate.

Next, in step S302, the operator places about <NUM> of sodium tartrate on the weighing dish 2a based on an instruction on the display unit <NUM>, sets the sodium tartrate by closing the lid <NUM>, and then starts measurement upon setting the heating temperature setting to <NUM>.

A heating temperature may be manually set by the operator or may be automatically set to the corresponding heating temperature by the moisture meter <NUM> in accordance with the type of standard substance.

Next, in step S303, the standard substance measurement unit <NUM> starts heating the heating unit <NUM>. The standard substance measurement unit <NUM> monitors a change in the mass measurement value of the mass measurement unit <NUM> as in the specimen measurement mode and at the same time measures a heating time T.

When the change in mass measurement value becomes not more than a predetermined threshold in step S304, the standard substance measurement unit <NUM> stops heating by the heating unit <NUM> and calculates the moisture content M of the standard substance according to equation (<NUM>) in step S305.

At the same time, in step S306, the standard substance measurement unit <NUM> calculates the time from the start of heating to the end of heating, that is, the heating time T. The process then shifts to step S203.

In step S203, the display unit <NUM> displays the moisture content M and the heating time T.

Next, in step S204, the storage unit <NUM> stores the calculated heating time T as the set heating time Ts, and the processing is completed.

<FIG> is a flowchart for explaining the operation of the moisture meter <NUM> in the inspection mode. The user of the moisture meter <NUM> can execute the inspection mode at an arbitrary time when he/she wants to inspect the presence or absence of an abnormality in the moisture meter <NUM>.

In step S401, the user sets the inspection mode via the input unit <NUM>. In step S402, the standard substance measurement unit <NUM> calculates the measured moisture content Mi of the standard substance and the measured heating time Ti as in steps S301 to S306.

Next, in step S403, the standard substance measurement unit <NUM> temporarily stores the measured moisture content Mi and the measured heating time Ti, measured in step S402.

Next, in step S404, the abnormality diagnosis unit <NUM> starts abnormality diagnosis. In step S405, the abnormality diagnosis unit <NUM> determines whether the measured moisture content Mi of the standard substance calculated in step S402 falls within a predetermined range with reference to the theoretical moisture content Mt. When, for example, sodium tartrate is used, the abnormality diagnosis unit <NUM> determines whether the moisture content falls within the range of <NUM> to <NUM>.

A predetermined range with reference to the theoretical moisture content Mt is set in accordance with the kind of standard substance. For example, a predetermined range may be set like a theoretical moisture content of ± <NUM>%.

When the measured moisture content Mi falls within the predetermined range in step S405 (Yes), the abnormality diagnosis unit <NUM> determines in step S406 that there is no abnormality in the mass measurement unit <NUM>.

In contrast to this, when the measured moisture content Mi falls outside the predetermined range in step S405 (No), the abnormality diagnosis unit <NUM> determines in step S407 that there is an abnormality in the mass measurement unit <NUM>.

Next, in step S408, the abnormality diagnosis unit <NUM> compares the measured heating time Ti measured in step S402 with a predetermined time Tp as the set heating time Ts stored in the inspection initialization mode to determine whether the measured heating time Ti is not more than the predetermined time Tp.

Note that the predetermined time Tp may not be strictly the same as the set heating time Ts and may be a time within a certain range such as the set heating time Ts of ±<NUM> sec.

When the measured heating time Ti is not more than the predetermined time Tp in step S408 (Yes), the abnormality diagnosis unit <NUM> determines in step S409 that there is no abnormality in the heating unit <NUM>.

When the measured heating time Ti is larger than the predetermined time Tp in step S408 (No), the abnormality diagnosis unit <NUM> determines in step S410 that there is an abnormality in the heating unit <NUM>. Causes for abnormalities in the heating unit <NUM> include, for example, contamination on the glass cover 9a, contamination on the heating means 3a, and a failure in the heating means 3a.

Next, in step S411, the abnormality diagnosis unit <NUM> displays diagnosis results on the display unit <NUM> and completes the processing.

<FIG> and <FIG> illustrate display examples of diagnosis results displayed on the display unit <NUM>. On each display, the button (highlighted in gray in <FIG> and <FIG>) on the image which is indicated by a black arrowhead 7a is the currently selected button. By selecting this button, a display screen is transitioned.

<FIG> is an example of display when it is determined in step S407 that there is an abnormality in the mass measurement unit <NUM>, and it is determined in step S409 that there is no abnormality in the heating unit <NUM>. When the user selects "Next" in the state of <FIG>, the abnormality diagnosis unit <NUM> displays, on the display unit <NUM>, a message for checking whether calibration has been performed as illustrated in <FIG>(B-<NUM>).

When no calibration has been performed, the user selects "No." The abnormality diagnosis unit <NUM> then determines that calibration is necessary and displays a message prompting execution of calibration on the display unit <NUM> as illustrated in <FIG>(B-<NUM>). Upon checking this message, the user executes calibration and selects the end button. Alternatively, the moisture meter <NUM> may be configured to automatically execute calibration.

Upon executing the calibration, the user executes measurement in the inspection mode again to check whether the abnormality has been eliminated. If the abnormality has not been eliminated even after the execution of calibration, the user selects "Yes" as illustrated in <FIG>(C-<NUM>).

The abnormality diagnosis unit <NUM> then determines that the abnormality in the mass measurement unit <NUM> has not been eliminated even after the execution of calibration and the moisture meter <NUM> needs to be repaired and displays a message prompting repair as illustrated in <FIG>(C-<NUM>). The user requests repair in accordance with the message.

<FIG> is an example of display when it is determined in step S406 that there is no abnormality in the mass measurement unit <NUM>, and it is determined in step S410 that there is an abnormality in the heating unit <NUM>. When the user selects "Next" in the state of <FIG>, the abnormality diagnosis unit <NUM> displays a message prompting cleaning of the glass cover 9a, on the display unit <NUM>, as illustrated in <FIG>, concerning contamination on the glass cover 9a among conceivable causes. Upon checking the message, the user cleans the glass cover 9a and selects "Next.

The abnormality diagnosis unit <NUM> then displays a message prompting cleaning of the halogen lamp (heating means 3a) on the display unit <NUM>, as illustrated in <FIG>, concerning contamination on the heating means 3a among conceivable causes. Upon checking the message, the user cleans the halogen lamp and selects "Next.

The abnormality diagnosis unit <NUM> then displays a message prompting replacement of the halogen lamp (heating means 3a) on the display unit <NUM>, as illustrated in <FIG>, concerning a failure in the heating means 3a among conceivable causes. Accordingly, the user makes a request to repair the halogen lamp.

At each of the stages of <FIG>, the display unit <NUM> displays the "End" button. By this button, the user may end the display of the diagnosis results halfway and execute measurement again in the inspection mode at his/her discretion.

For example, referring to <FIG>, when the user firmly believes that contamination on the glass cover 9a is the cause and cleaning the glass cover 9a will eliminate the abnormality in the heating unit <NUM>, the user may select "End" and execute measurement in the inspection mode again. This makes it possible to shorten the time required for inspection.

The moisture meter <NUM> according to the present embodiment is configured to diagnose the presence or absence of an abnormality in the mass measurement unit <NUM> by measuring the moisture content of the standard substance in the inspection mode and evaluating the measured moisture content Mi with respect to the theoretical moisture content Mt of the standard substance and determine an abnormality in the heating unit <NUM> by measuring the heating time required for measurement of the moisture content of the standard substance and comparing the measured heating time Ti with the predetermined time Tp as the set heating time Ts at the time of shipment. This makes it possible to diagnose the state of the moisture meter <NUM> in consideration of not only causes of the mass measurement unit <NUM> but also causes other than the mass measurement unit <NUM>, especially the state of the heating unit <NUM>.

The moisture meter <NUM> is configured in particular to compare the measured heating time Ti with the predetermined time Tp as the set heating time Ts in abnormality diagnosis for the heating unit <NUM> and determine the presence of an abnormality in the heating unit <NUM> when the measured heating time Ti is longer than the predetermined time Tp. This makes it possible to diagnose the presence of a failure, such as contamination on the glass cover 9a or the halogen lamp (heating means 3a) or a failure in the halogen lamp (heating means 3a), which increases the time required for measurement.

Claim 1:
A moisture meter (<NUM>) comprising:
a mass measurement unit (<NUM>) configured to measure a mass of a specimen placed on a weighing dish (2a);
a heating chamber (C) having the weighing dish (2a) placed inside and configured to open and close;
a heating unit (<NUM>) placed in the heating chamber (C) and configured to heat the specimen;
a control arithmetic unit (<NUM>) configured to control the heating unit (<NUM>) to heat the specimen until a change in mass of the specimen becomes not more than a predetermined threshold and calculate a moisture content of the specimen from the change in the mass of the specimen before and after heating;
a timepiece (<NUM>) configured to measure a heating time; and
a storage unit (<NUM>),
wherein the heating unit (<NUM>) includes a heating means (3a),
the heating chamber (C) includes a glass cover (9a) to prevent the specimen from coming into contact with the heating means (3a),
the control arithmetic unit (<NUM>) includes a standard substance measurement unit (<NUM>) configured to measure a moisture content of a standard substance for inspection as the specimen and measure a heating time, and
an abnormality diagnosis unit (<NUM>) configured to diagnose presence or absence of an abnormality in the mass measurement unit (<NUM>) by evaluating whether the measured moisture content falls within a predetermined range with reference to a theoretical moisture content of the standard substance, and wherein
the standard substance has a known theoretical moisture content and a known appropriate heating temperature for a measurement of moisture content,
characterized in that the storage unit (<NUM>) stores, as a set heating time, a heating time that is calculated when a moisture content of the standard substance is measured when heated at the appropriate heating temperatures,
the abnormality diagnosis unit (<NUM>) is configured to diagnose presence or absence of an abnormality in the heating unit by comparing a measured heating time with a predetermined time as the set heating time stored in the storage unit (<NUM>),
wherein the abnormality diagnosis unit (<NUM>) determines that there is an abnormality in the heating unit (<NUM>) when the measured heating time is longer than the predetermined time, and
wherein the determined abnormality is contamination on the glass cover (9a) or contamination on the heating means (3a).