JP2535085B2 - Heating / drying type moisture meter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-drying type moisture meter, and more particularly to a heat-drying type moisture meter adapted to perform zero point correction during measurement.

[Description of Prior Art] The heat-drying type moisture meter measures the weight of a sample to be measured placed in a sample dish by drying it with heat from infrared rays or the like, and measures the moisture content of the sample from the weight change due to heating and drying. To do. That is, assuming that the moisture value is M, the initial load of the sample including the sample dish is W0, and the same weight after heating and drying for t hours is Wt, the moisture value M is obtained by the following formula.

M = (W0-Wt) / W0 Wt is treated by heating and drying. That is, the heating / drying type moisture meter is designed to measure the Wt value every second. It is no exaggeration to say that the heat-drying type moisture meter is composed of a weight measuring machine. A load cell such as a load cell is used as the weight measuring machine, but this load cell needs to perform zero compensation even during the measurement period. For this reason, the load of the sample pan or the like is removed from the pedestal of the load meter during heating and drying, and the zero point compensation is performed. The applicant is
A heat-drying type moisture meter having a mechanism for lifting the sample dish from the pedestal of the load meter to remove the load is proposed in Japanese Utility Model Publication No. 63-6323.

FIG. 4 and FIG. 5 are schematic sectional views of the heat-drying type moisture meter disclosed in Japanese Utility Model Laid-Open No. 56-6323.

FIG. 4 shows that the sample pan 48 is placed on the pedestal 46 and the load cell is
A load is applied to 44, the lamp housing 50 is covered on the sample dish 48, and the infrared ray 51, which is an internal heat source, radiates heat rays to the sample in the sample dish to heat and dry the sample. A windshield 52 having a peripheral wall is provided around the sample dish 50 and the pedestal 46, and the upper end peripheral edge of the windshield 52 is aligned with the lower end peripheral edge of the lamp housing 50 through a slight gap G. The bottom part of the windshield 52 is fixed on the upper wall surface of the main body 53 in which the load meter 44 is housed, and the load receiving shaft 45 of the load meter 44 penetrates through a round hole penetrating the upper wall of the main body 53 and the bottom part of the windshield 52. And has reached the cradle 46. Reference number 43
Is an elevating mechanism for appropriately elevating the sample dish 46 from the pedestal 46.

FIG. 5 is a similar cross-sectional view of the same heating / drying type moisture meter. In the case of this figure, the sample pan 48 is moved by the lifting mechanism 43 to the pedestal 46 during the measurement for the zero point compensation of the load meter 44. It shows a state of being elevated from. In this state, since the cradle 46 is not loaded, it is possible to read the indicated value of the load meter 44 and perform zero point compensation.

By the way, since heat rays are emitted from the infrared lamp, air flow occurs in the lamp housing 51 due to a convection phenomenon. For example, the flow of air like the arrow in the figure
This air flow affects the load measurement as an error. That is, since the large air flow fa is blocked by the windshield 52, the load error is almost eliminated. However, in addition to the above air flow fa, the air flow passing through the gap between the load receiving shaft 45 and the through hole that penetrates the upper wall of the main body 53 and the bottom of the windshield 52.
A force for pushing up the pedestal 46 and the sample dish 48 is generated at fb, which causes an error of minus the load. This error is due to the air flow
It was difficult to correct this error because fb varied due to various factors such as the size and shape of the components of the heating and drying moisture meter and the manufacturing error thereof, the heating temperature of the lamp, and the elapsed heating time.

Especially, the sample dish with a large area where this air flow fb acts.
The influence of weight error due to 48 is large. The zero point compensation performed before the measurement is performed in a state where the sample dish is not placed on the receiving table 46 (FIG. 5). Since the air flow fb at the time of zero point compensation mainly acts on the pedestal 46 having a small area, the weight error due to this is small. Assuming that the weight error is w and the weight error W is the weight of the sample pan 48 placed on the pedestal 46 (FIG. 4), the weight error ratio w / W is about 1/10 according to the experiment. Although the weight error w can be corrected at the time of zero point compensation, the large weight error W in the state where the sample pan 48 is placed on the pedestal (Fig. 4) is corrected because the sample being heated and dried is put in the sample pan 48. Can not.

[Problems to be Solved by the Invention] An object of the present invention is to provide a heating and drying type moisture meter in which the error caused by the above air flow is reduced.

[Means for Solving the Problem] Therefore, according to the present invention, a sample pan in which a sample to be measured is placed, a main body, a load meter arranged in the main body for measuring the load of the sample pan, and a sample placed on the load meter A pedestal for arranging the dish, a housing for enclosing the sample dish placed on the pedestal from above, a heating means disposed in the housing for heating and drying the sample to be measured in the sample dish, and the sample dish In the heat-drying type moisture meter having a load removing means for removing the load, the heat-drying type moisture meter is provided with a convection canceling plate covering the lower part of the sample dish in the pedestal. .

[Operation] According to the above configuration, since the convection counter plate that covers the lower side of the sample dish is provided, it is possible to measure the sample weight and the zero point.
The air flow fb passing through the gap acts on the convection counter plate equally. That is, when measuring the sample weight (Fig. 1), the error due to the air flow fb from the gap is not due to the sample pan alone but due to the convection canceling plate 7 enclosing the sample pan from below, and this error is zero point. It can be corrected at the time of correction. That is, the error due to the air flow fb from the gap can theoretically be zero by providing the convection canceling plate. However, depending on the weight of the sample pan, the position of the plate is different depending on the weight of the sample pan, and there is a slight difference in the effect of convection. I can't. However, according to the experimental results of the applicants, the error for this is 1/100 of the above error W, that is, 0.01 W, which is extremely small.

[Example] The present invention will be described in the form of an example using a heating and drying type moisture meter in which an electronic balance is used as a load meter.

Referring to FIG. 1, a windshield 2 extending upward from a load meter 4 housed in a main body 10 and fixed to the upper wall of the main body and the former.
Pedestal 6 provided at the upper end of the load receiving shaft 5 that penetrates the bottom of the
The plate is provided with a dish-shaped convection canceling plate 7. As shown in FIG. 3, the canceling plate 7 has a protrusion 7a having a slight height formed on the upper surface thereof, and the sample plate 6 is placed on the protrusion 7a.
Are arranged. Further, the counter plate 7 is provided with a through hole 7b. In the through hole 7b, a support rod 31 for the lifting mechanism 3 that extends vertically through the through holes 2b and 10b provided in the upper wall of the main body 10 and the bottom wall of the windshield 2 provided in the main body 10.
Come and go. That is, at the time of measurement at the time of zero point compensation, the elevating mechanism 3 operates and the supporting rod 31 ascends, and the sample pan 8 is pushed up through the through hole 7b and lifted from above the projection 7a (Fig. 2). Therefore, the weight applied to the pedestal 6 is removed, and the measurement for zero point compensation becomes possible. The tip of the support rod 31 has a through hole 7b even during normal measurement.
It is desirable that it rushes in. This is because, by this, the conditions of the air flow passing through the through hole 7b can be made substantially equal during the normal measurement and the zero point compensation measurement. Similarly, the protrusion 7a also creates a gap between the lower surface of the bottom of the sample dish 8 and the upper surface of the offset plate 7 during normal measurement so that the lower surface of the bottom of the sample dish 8 does not block the through hole 7b. The condition of the air flow by convection is made as uniform as possible regardless of whether the dish 8 is above or below. Although there is some difference in the air flow depending on the upper and lower sides of the sample dish 8, the influence of this error is slight. Therefore, the size of the cancel plate 7 is set so as to cover the lower side of the sample dish 8 and the air flow by convection does not act on the sample dish 8.

In FIG. 1, reference numeral 9 is a lamp housing and reference numeral 1 is an infrared lamp.

Although the present invention has been described in the form of embodiments, the present invention is not limited to the above embodiments and can be variously modified within the scope of the claims.

For example, the lifting mechanism 3 for lifting the sample pan 8 from the pedestal 6 has been described as a mechanical one. However, it is also possible to magnetically pull the sample pan 8 from above, and the bottom part of the sample pan 8 may be used. Alternatively, a protrusion may be provided and the sample dish may be displaced from the protrusion 7a by lateral movement or rotation.
In this case, since it is not necessary to provide the through hole 7b in the cancel plate 7, the influence of the convection air flow can be further reduced.

[Brief description of drawings]

1 and 2 are sectional views showing a heating and drying type moisture meter according to an embodiment of the present invention. FIG. 1 shows a case of normal measurement, and FIG. 2 shows zero point compensation. This is the case of measurement. FIG. 3 is a view showing a top view of the offset plate of the moisture meter shown in FIG. 1. 4 and 5 are cross-sectional views of a conventional heat-drying type moisture meter, FIG. 4 shows a case of normal measurement, FIG. 5 shows a case of zero-point compensation measurement, and FIG. The drawing is an enlarged cross-sectional view of FIG. 1 for showing the details of the air flow. 1 ... Infrared lamp, 2 ... Windshield, 3 ... Lifting mechanism, 4
…… Load cell, 5 …… Load receiving shaft, 6 …… Bed, 7 ……
Convection offset plate, 7a ... Protrusion, 7b ... Through hole, 8 ... Sample dish, 9 ... Lamp housing, 10 ... Main body, 31 ... Support rod.

Claims (1)

(57) [Claims] 1. A heating / drying type moisture meter, a sample pan for containing a sample to be measured, a main body, a load meter arranged in the main body, for measuring the load of the sample pan, and mounted on the load meter. A pedestal for arranging the sample dish, a housing surrounding the sample dish arranged in the pedestal from above, and a heating unit disposed in the housing for heating and drying the sample to be measured in the sample dish, In the heating and drying type moisture meter having a load removing means for removing the load of the sample dish, the pedestal is
A heat-drying type moisture meter, characterized in that a convection counter plate that covers the bottom of the sample dish is provided.