JPS6156461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature compensation method and apparatus for an electrical resistance moisture meter.

An electric moisture meter utilizes the correlation between the moisture content of an object to be measured (hereinafter referred to as a sample) and its electrical properties, such as electrical capacity and electrical resistance. However, the electrical properties of the sample change depending on the moisture content, and also change depending on the temperature of the sample.

The magnitude of change in electrical properties due to temperature is approximately ±1.0% in terms of moisture change for a temperature change of ±10°C when measuring grain moisture using an electrical resistance method, and is usually 0.1%/1. Moisture temperature correction is performed in °C. In order to accurately perform this temperature correction, it is necessary to detect the temperature of the sample, but in the case of an electric moisture meter that measures moisture by crushing the sample and applying pressure, it is necessary to measure a small amount of sample between narrow electrodes. Since it is difficult to insert a sensor that detects sample temperature into the sample between the electrodes, a temperature detection sensor is usually placed near the electrodes, and the moisture temperature is corrected using the detected temperature.
In this method, when measuring moisture content by crushing the sample and applying pressure between the electrodes, heat is exchanged between the sample and the electrode metal, and at the time of moisture measurement, the sample temperature approaches the electrode temperature, and the initial sample temperature and electrode The difference is about 1/3 of the difference from the temperature, so it is used as something that does not cause a large error. That is, if the initial difference between the sample temperature and the electrode temperature is 10°C, there will be a difference of about 3°C at the time of moisture measurement, and even if the moisture temperature is corrected using the temperature near the electrode, the error will be 0.3%.

However, in recent years, thermal drying of grains has become popular,
Grain being dried is taken out and its moisture content is measured. In such cases, the difference in temperature between the initial grain and the vicinity of the electrode is often 10°C to 20°C, so the moisture temperature must be corrected. Errors cannot be ignored.

An object of the present invention is to detect sample temperature and improve temperature correction accuracy.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 A to C are examples of the electrode structure of an electrical resistance moisture meter. Figure 1 A is a type in which the sample is crushed between the electrodes and pressurized, and Figure 1 B is a type in which a pre-pulverized sample is applied between the electrodes. The pressure type, Fig. 1 (c), is the type that measures moisture while crushing and pressurizing with a roller electrode.
In the case of the electrode structures shown in Figure 1 A and B, when the sample is pressurized between the electrodes, heat is exchanged between the sample and the electrodes.
Due to the difference in heat capacity between the electrode and the sample, the temperature of the electrode hardly changes, but the temperature of the sample approaches the temperature of the electrode. Its characteristics are shown in Figure 2.

In Figure 2, the electrode temperature is 20℃ and the initial temperature of the sample.
T ₀ is 30 °C for A ₁ , 20 °C for B ₁ , and 10 °C for C _1. The sample temperature approaches the electrode temperature with time, but within a few seconds, the difference between the sample temperature and the electrode temperature decreases from the initial value. This is about 1/3 of the difference. The amount of change in sample temperature increases as there is a difference between the initial sample temperature _T0 and the electrode temperature.If the sample temperature and electrode temperature are equal from the beginning, as shown in B1 in Figure ₂ , the change in sample temperature do not have.

A ₂ , B ₂ , and C ₂ in Figure 3 are the temperature-uncorrected moisture meter outputs that change over time when a sample with a constant moisture content is measured under the same conditions as A ₁ , B ₁ , and C ₁ in Figure 2. It shows the characteristic that This time change in the temperature-uncorrected moisture meter output represents a change in the resistance value of the sample, and after the initial change in resistance value due to a change in crushing pressure, it represents a change in resistance value due to a change in temperature of the sample. The temperature-uncorrected moisture output in FIG. 3 excluding the initial sample applied pressure fluctuation portion corresponds to the sample temperature change in FIG. 2, and a 1°C change in sample temperature results in a 0.1% change in the moisture meter output. Therefore, changes in the sample temperature can be determined from changes in the moisture meter output signal without temperature correction.

Figure 4 shows the time when the sample is loaded or squeezed between the electrodes.
It is a characteristic diagram in which M ₁ and M ₂ are the moisture meter outputs without temperature correction at t ₁ and t ₂ (t ₁ < t ₂ ) with t ₀ as the starting point. In FIG. 4, A ₃ , B ₃ , and C ₃ represent cases where the sample temperature is higher than the electrode temperature, and indicate cases where the difference between the sample temperature and the electrode temperature is large, small, and zero, respectively, and M ₁ − The value of M ₂ corresponds to the temperature change of the sample, and the larger the difference between the initial sample temperature T and the electrode temperature T ₀ , the larger it becomes. Therefore, when it is proportional to T - T ₀ , it can be approximated to the first order.

That is, if T-T ₀ ∝M ₁ -M ₂ and K' is a constant of proportionality, then T=T ₀ +K' (M ₁ -M ₂ )...(1).

FIG. 5 is a characteristic diagram showing how the sample temperature changes over time. In Figure 5, when the difference between the initial temperature T of the sample and the electrode temperature T ₀ is large, the characteristic is A ₄
, and the small case is characteristic B ₄ , and the larger T-T ₀ is, the larger the change in sample temperature is.

Therefore, the sample temperature T ₂ and the electrode temperature at time t ₂
Since the difference from T ₀ becomes larger as the difference between the initial sample temperature T and the electrode temperature T ₀ becomes larger, T ₂ −T ₀ can be linearly approximated when it is proportional to T − T ₀ .

That is, T ₂ −T ₀ ∝T−T ₀ . Substituting the above first equation into this, T ₂ −T ₀ ∝K′(M ₁ −M ₂ )…(2) Therefore, the second equation becomes T ₂ =T ₀ +K(M ₁ −M ₂ )… It can be approximated as (3).

Here, K is a proportionality constant determined by the structure and material of the electrode, the type of sample to be measured, etc. In order to obtain a more accurate sample temperature T ₂ , T ₂ is given by a higher-order expression of M ₁ −M ₂ . Note that the electrode temperature T ₀ is detected by installing a temperature sensing element near the electrode.

FIG. 6 is a block diagram of one embodiment of an electric moisture meter for realizing the temperature correction of the present invention, in which a timer in a microprocessor section 6 is started by the sample set switch means 4 which notifies that a sample has entered the electrode. After Δt time, at _t1, the transfer switch 8A is closed, and the signal from the electrode section 1 is linearized, level adjusted, etc. in the converter section 2, and is input to the A/D converter 5, which performs A/D conversion. The converted digital signal is read by the microprocessor 6 and processed as data.
Let D be ₁ . Furthermore, at time t ₂ , the signal from the electrode is also read and set as D ₂ . The signal converter 2 converts the data D ₁ and D ₂ into temperature-uncorrected moisture signals M ₁ and M ₂ .
If not, the microprocessor 6 calculates D ₁ and D ₂ using a predetermined moisture conversion formula to obtain uncorrected temperature signals M ₁ and M ₂ . Next, the transfer switch 8B is closed, the electrode temperature signal from the temperature detection section 3 is input to the A/D conversion section 5, and its output is read by the microprocessor 6 to obtain electrode temperature data _T0 . Here, the microprocessor 6 is broadly defined and includes input/output ports, ROM, RAM, etc. Furthermore, if the time t ₁ is set to about 1 second after the start of the measurement, and the time t ₂ is set several seconds later, the moisture measurement time can be a few seconds. The switches 8A and 8B are analog switches with gates. The microprocessor 6 uses these data M ₁ , M ₂ , T ₀ and a predetermined constant K to calculate the third equation T ₂ =T ₀ +K(M ₁ −M ₂ ).
Calculate.

This sample temperature _T2 , temperature uncorrected moisture signal _M2 , and predetermined temperature correction coefficient (0.1%/1℃)
Calculate by substituting the temperature-corrected moisture content M of the sample into the equation M=M ₂ −α(T ₂ −20) (4). α is a constant determined by the type of sample.

Here, the temperature correction is based on 20°C, and the uncorrected temperature moisture signal _M2 is sent to the signal converter 2 so that it directly indicates the moisture content of the sample when the sample temperature is 20°C.
An arithmetic expression for the moisture uncorrected signal _M2 is designed from the output level of the microprocessor 6 or the read data _D2 from the microprocessor 6. This temperature-corrected moisture content M of the sample is output to the moisture display device 7.

By using the temperature correction method and device according to the present invention, it is possible to correct the true moisture content according to the sample temperature,
It is possible to measure the moisture content of high-temperature grains during thermal drying with little error, and it is possible to finish the grains so that they have an appropriate moisture content without being over-dried or under-dried.

[Brief explanation of the drawing]

Figure 1 A to C are diagrams each showing an example of the sample electrode structure of a moisture analyzer, Figure 2 is a characteristic diagram of time versus sample temperature, and Figures 3 and 4 are time versus temperature based on experimental data. The characteristic diagram of the uncorrected moisture meter output, Figure 5, is
FIG. 6, which is a characteristic diagram of time versus sample temperature, is a block diagram of a temperature correction device for a moisture meter according to an embodiment of the present invention. E...Sample electrode, G...Sample, 1...Sample electrode, 3...Temperature detection element, 4...Sample set switch, 8A, 8B...Transfer switch, 6...Microprocessor, 7...Moisture display Device.

Claims (1)

[Scope of Claims] 1. In a temperature correction method for an electrical resistance moisture meter in which the temperature of the object to be measured is balanced with the temperature of the measurement electrode section, each At t ₁ and t ₂ after different fixed times, the electrical resistance of the object to be measured is measured to obtain a temperature-uncorrected moisture signal, and according to the difference in the temperature-uncorrected moisture signal between t ₁ and t ₂ , The difference between the temperature at the time of loading the electrode part of the object to be measured and the temperature of the electrode part is calculated from the estimation formula based on the time-temperature uncorrected moisture signal characteristic data determined in advance, and the difference between the temperature at the time of loading the electrode part of the object to be measured and the temperature of the electrode part is calculated from the result and the temperature of the electrode part at t ₁ o'clock. Alternatively, a temperature correction method for an electric resistance moisture meter that calculates the temperature of the object to be measured at t ₂ and corrects the temperature-uncorrected moisture signal at t ₁ or t ₂ based on those temperatures. 2. The method according to claim 1, wherein the temperature of the assembly of the electric moisture meter, the temperature near the assembly, or the temperature near the electrode section is used as an approximate value of the temperature of the electrode section. 3. The method according to claim 1 or 2, wherein the electrical resistance measurement time has a relationship of t ₁ <t ₂ , and t ₂ is set sufficiently earlier than the temperature equilibrium time. 4. The method according to claim 1, 2, or 3, wherein the electrode portion has a larger heat capacity than the object to be measured. 5. In a temperature correction device for an electrical resistance moisture meter in which the temperature of the object to be measured is balanced with the temperature of the measurement electrode section, the microprocessor and the object to be measured are loaded or clamped on the electrode section. A timer means for starting counting, and at t ₁ and t ₂ (t ₁ < t ₂ ) after the start of counting, the temperature-uncorrected moisture measurement signals M ₁ and M ₂ of the object to be measured are sent from the measurement electrode section, and It includes a signal acquisition means for taking out a signal T ₀ representing the temperature of the measurement electrode section, A/D converting it, and inputting it into the microprocessor, and in the microprocessor, the sample temperature T ₂ =T at time t ₂ is obtained. ₀ +K(M ₁ −
M ₂ ), where K calculates a proportionality constant determined by the structure, material, and object of the electrode part, etc., calculates the temperature-dependent moisture value based on the result, and displays the temperature-corrected moisture measurement value on the moisture display section. Temperature correction device for a moisture meter that displays 6 The temperature-corrected moisture value M is the calculated value of T ₂ as M = M ₂ - α (T ₂ - T _A ) (where α is the temperature coefficient determined by the object to be measured, and T _A is the temperature correction standard. 6. The temperature correction device for a moisture meter according to claim 5, wherein the temperature is calculated by substituting the temperature into an arithmetic expression (temperature).