Gravimetric moisture-determination instrument with an air duct for cooling

Abstract

A measuring instrument (1) for gravimetric moisture determination consists of an instrument housing (2), a balance (3) installed in the instrument housing, and a radiant heater (8). The moisture content of a sample on a tray placed on the tray carrier (5) is determined by measuring the weight loss of the sample while it is being dried under the heater. The instrument is equipped with means for conducting an air stream generated by a fan (12) through the space between the sample tray carrier (5) and the weighing cell (21). The air-conducting means include an air duct that can be at least partially released from the instrument housing for cleaning.

Description

[0001] The invention relates to a gravimetric moisture-determination instrument that is cooled by an air stream. In essence, the instrument consists of a housing containing a balance and a radiant heater. The moisture content of a sample placed on the balance pan is determined by measuring the weight loss of the sample while it is being dried under the heater.[0002] Instruments for the gravimetric determination of moisture content are known and commercially available. They share as a common operating principle that a sample whose moisture content is to be determined is placed on a balance that continuously monitors the weight of the sample while the latter is being heated, normally by a conventional infrared radiator or halogen radiator. As a result of the heating, moisture is evaporated from the sample, which causes a weight loss that is measured by the balance. A variety of arrangements are used for placing the sample into the moisture-determination instrument. In one arrangement,...

AI Technical Summary

Benefits of technology

[0006] In a gravimetric moisture-determination instrument equipped with an air duct between the balance pan, the weighing cell, and a pan-supporting load-receiver that is attached to the weighing cell, the present invention aims to improve the design of the air duct so that the latter can be cleaned in a simple routine procedure.

[0007] The invention solves this problem by proposing an arrangement where at least a part of the air duct is removable from the housing for cleaning. The gravimetric moisture-determination instrument according to the invention consists of a balance installed in a housing, as well as a heat source located above the balance, which heats the sample to evaporate the moisture from it, so that the moisture content can be determined from the weight loss of the sample. Between the heat source and the weighing cell of the balance, more specifically between the balance pan (or sample tray) and the weighing cell, the instrument contains means for conducting an air stream, e.g., propelled by a cooling fan. The air-conducting means include an air duct that can be released from the housing in a simple way for cleaning. The invention has the advantage that it eliminates the complicated and--after a time--expensive replacement of filter pads and, in addition, that the aforementioned cleaning procedure has to be performed less frequently than the filter replacement. If the ventilating means require cleaning at all, which may happen in the case of a very dusty environment, the cleaning procedure can easily be done by the user, so that it will not be necessary to call in a service technician to disassemble and clean the air duct.

Problems solved by technology

As a result of the heating, moisture is evaporated from the sample, which causes a weight loss that is measured by the balance.

If the moisture-determination instrument of the foregoing description is used in a dusty or exceptionally dirty environment, there is a risk that the dust particles from the ambient air may clog up the filter pad in a very short time, so that filter pads have to be replaced on a frequent or even daily basis.

The problem with replacing the filter pads is that users may neglect to do it, particularly if the filter pad is set in a holder that is complicated to unscrew, as is the case with commercially available moisture-determination instruments of the kind where the balance is fixed in the housing and the heater is movably mounted above the balance.

If the filter pad is not replaced when needed, the clogged-up filter will obstruct the passage of air, so that the instrument is no longer cooled properly.

Although it is conceivable to use the instrument without the filter pad, this will over time lead to an accumulation of dust in the air duct which can make the cooling action less effective.

This can make it necessary to clean the air duct from time to time in a complicated procedure requiring a partial disassembly of the instrument.

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