JPS6157819A - Measurement system for temperature - Google Patents

Abstract

PURPOSE:To measure the temperature of a heating resistor at a high speed with high precision by calculating variation in the temperature of the heating resistor from the detected value of variation in voltage or current appearing at the heating resistor by impressed electric power and the detected value of variation based upon only variation in impressed electric power. CONSTITUTION:The series circuit of the heating resistor Rh and a detection resistance Rs is impressed with a voltage E from a power source 1 to develope a voltage Vh across Rh and a voltage V across Rs. The series circuit of Ra and Rb connected in parallel to said series circuit generates a reference voltage equal to the voltages Vh and V when a resistance value is Ro at reference temperature To, and a small sresistance-temperature coefficient among Rs, Ra, and Rb is used. Then, Rs detects variation of the current flowing through Rh, i.e. variation due to variation in voltage E and temperature variation in the resistance value of Rh with the voltage V, and Rb detects the detected value corresponding only variation in voltage E with the voltage Vo on the basis of the detected value of Rs at the temperature to of Rh. The voltages V and Vo are processed by a divider to measure the temperature of the heating body at a high speed with high precision.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature measurement method, and in particular, the present invention relates to a temperature measurement method, in which the applied power is applied at high speed based on the resistance change during driving of the heating resistor of a thermal head used in a thermal transfer printer, etc. The present invention relates to a temperature measurement method that can accurately measure the temperature of a heating resistor when the temperature changes.

In recent years, technological advances in printing devices have been remarkable, and in particular, thermal transfer printers using thermal head drive devices are developing high-speed, multi-gradation color printing technology that does not produce noise during printing.

By the way, the basis of multi-gradation thermal transfer printer technology is a means to quickly control the temperature of a heating resistor corresponding to multiple gradations. Need to be established. However, there is currently a lack of suitable measurement methods, and there is an urgent need for the development of measurement techniques.

[Conventional technology]

Special thermistors, thermocouples, infrared microscopes, etc. for high-speed response have been used to measure the temperature characteristics of heat-generating resistors when applied power changes rapidly, but these two methods cannot achieve high accuracy. The latter was difficult and extremely expensive. Moreover, in either case, measurement was impossible without direct contact with the heating resistor. Further, as another method, there is a method of measuring the temperature change of the heating resistor, but there is a problem in that it is usually possible to measure only the temperature-high characteristic during binary driving.

As is well known, when the temperature of a typical heating resistor changes, the resistance value of the heating resistor also changes. Therefore,
If you precisely measure the applied voltage and the current flowing at that time,
This means that the temperature of the heating resistor can be calculated. BACKGROUND ART Conventionally, a method has been widely used in which a Wheatstone bridge or the like is used to precisely measure a change in resistance value in a steady state of a platinum resistance wire or the like having a stable resistance-temperature coefficient.

However, there has been little testing of the case where the applied power changes rapidly. Binary drive, i.e.
7. When the drive power is ON'' and OFF'',
Attempts have been made to measure the resistance value of the gas, but it is an incomplete method that measures only the gastric resistance at a temperature limited to the period when the driving power is ON.

FIG. 564 shows a conventional measurement circuit for a heating resistor.

In the figure, E is the power supply voltage value, Ilh is the resistance value of the heating resistor, Rs is the resistance value of the minute detection resistor for detecting the current flowing through the heating resistor, ■ is the voltage value across the detection resistor, and S
indicates a power switch. The voltage V is given by the following equation.

V-E-R5/(Rh + R3)... ■The resistance temperature coefficient of the heating resistor is α, the resistance value of the heating resistor at temperature To is Ro, and the resistance value at temperature Tt is Rt, Let α be a constant value defined by the following equation.

tx= ((Rt-1?o)/Ro) Xl06/(T
t-To) ・・・・■ Let the temperature of the heating resistor at any time be Th, and the resistance value Rh of the heating resistor is expressed by the formula ■
Based on the resistance value Ro at the temperature To, Rh=Ro・αo・(Th−To) 10R.

=Ro ・(1+cxo ・(Th−To)) ・・・
■However, α. -10-6α.

In the formula ■, the temperature change Th −To from the temperature To is expressed as Δ
If we set it as T, then Rh = Ro・ (1+α0ΔT)・・・・・
・■ Substituting the formula ■ into the formula ■, V = E ・Rs/ (Ro ・(1+αoΔT)0Rs) ・・■Here, the detection resistance Rs is negligibly small compared to the resistance Rh of the heating resistor. Because it is necessary, R
When performing a near-value calculation assuming O>R3% and 1>α0, V
=E-Rs・(T to 1%)/Ro...■, and it can be seen that the voltage ■ has a substantially linear relationship with the temperature change ΔT.

As is clear from 20, with this measurement method, measurement cannot be performed when the applied power is zero, that is, when the binary drive is OFF, and even when the applied power changes, the voltage V of the detection resistor changes. It is not possible to determine whether this is caused by a change in the temperature of the heating resistor or a change in the applied power.

Basically, at 2■ and ■, the measurement voltage ■ is set to the power supply voltage E.
The variation in applied power can be removed by dividing by .

However, since the change in the measured voltage (2) due to temperature change is small, while the change in the power supply voltage (E) can be large, the accuracy of the divider must be extremely high, which has the disadvantage that it cannot be put to practical use.

Furthermore, it was not possible to measure the temperature drop characteristics when the drive power was OFF.

[Problem that the invention seeks to solve]

In view of the conventional problems mentioned in section 2, the present invention provides means for calculating the temperature of a heating resistor without depending on changes in applied power.
The purpose of the present invention is to provide a temperature measurement method that can measure temperature without contacting a heating resistor, has high accuracy, high response speed, and is inexpensive.

[Means to solve the problem]

The purpose of this is to provide means for maintaining the electric power applied to the heating resistor at a predetermined micropower or higher in a method of measuring temperature by detecting the resistance value of the heating resistor, and means for detecting a change in voltage or current appearing on the heating resistor; means for detecting a change based only on a change in the applied power included in the detected value; and each detected value of the two detecting means. This is achieved by providing a temperature measurement method characterized in that a divider is provided as a calculation means for calculating the temperature change of the heating resistor from .

[Effect]

That is, according to the present invention, when the power applied to the J heating resistor changes, the 4' I+
(Predetermined tii & small power 1) where the change in resistance value of the antibody can be measured, and divide the change in resistance value using 2:;
(1)+' to convert the applied power to 'C'.

First, you can measure the temperature of the 11 bodies that generate heat in front of you. 1.) It is 1° above C.

〔Example〕

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

FIG. 1 shows a circuit diagram of the crystallinity measuring method of the present invention.

In order to make the explanation of the configuration and operation easier to understand, the same parts are given the same reference numerals throughout all the figures and all the formulas.

In the figure, 1 indicates a power supply and 2 indicates a divider. A power supply voltage E applied to the series circuit of the heating resistor Rh and the detection resistor Rs generates a voltage vh in the heating resistor Rh and a detection voltage ■ in the detection resistor Rs. Resistor 1 connected in parallel to this series circuit? The series circuit of a and Rh is heating resistor 1? The voltage vh when h is the resistance value Ro at the reference temperature To
A balance resistor is used that produces a reference voltage equal to (1) and (2), and each resistor Rs, Ra, Rh has the same small resistance-temperature coefficient.

Then, the voltages across the resistors Ra and Rb are respectively Va.
.

Vo is set, and Va is arranged so as to correspond to voltage vh.

When configured in such a parallel circuit, the detection resistor Rs No. 11
Total 61I (change in current flowing through antibody Rh, i.e.,
A change in current due to both a change in the power supply voltage E and a temperature change in the resistance value of the heating resistor 11h is detected using the voltage V. On the other hand, the temperature of the heat generating resistor Rh is 1゛o.
With reference to the detected value of the detection resistor Rs that changes over time, a detected value corresponding to only a change in the power supply voltage E is detected at the voltage ν0.

Detection fl (detection voltage V generated at anti-Rs is calculated from equations ■ and ■: V −E −Rs / (Rh +Rs) = P
, -R8/ (RO・(1+(xo・8T)
→−R3] ・ ・ ■Balance resistance 1 again? The detected voltage Vo generated at h is expressed by the equation (■), assuming ΔT=0, and the difference Vx between the voltages V and Vo is expressed by the equation (■) and the peak. ) from ν
x=V −ν0 =E−Rs・[+/ (Ro・(1+ffo HΔTl
1h11/(Ro+Rs)] -E-R3-Po·α.・ΔT/ [(Ilo(Ll
α++ ・Δ1゛)”-R3〕・(Ro)R8)】・・
・・・・・・Substituting the formula ■ into 〇〇 gives x−■・ΔT・αo−Ro/ (llo+Fls)
・・・−・(fΦ, ゛, Δ T=Vx ・
(Ro1Rs) / (V ・ (Xo −
Ro) ・ @In other words, by calculating ν with /V and other known values with divider 2, the temperature change ΔT of the heating resistor or the temperature Th of the heating resistor can be obtained without reply from 2〇. .

In order to keep the minimum value of applied power above a certain value, it is necessary to install a circuit that detects the applied power, and when this becomes less than a certain value, switch to another power source that guarantees the minimum value of applied power. good.

FIG. 2 shows an example of a power supply circuit used in the present invention. In the figure, numeral 3 denotes a variable power supply with a voltage Ev, numeral 4 a fixed power supply that outputs the minimum value Ef of the applied voltage, and Dv and Df each represent a diode. When the voltage Ev of the variable power supply 3 is greater than the voltage Ef of the fixed power supply 4, the diode Dv is conductive, the diode Of is non-conductive, and the output voltage E is I! Equal to v. Further, when the voltage ljv of the variable power supply 3 is lower than the voltage Ef of the fixed power supply 4, the diode Dv is non-conductive, the diode Df is conductive, and the output voltage E is equal to E[, so that the minimum voltage is guaranteed.

When performing bidirectional driving, it is possible to prepare a power supply that applies the corresponding applied power when OFF" and switch between ON" and OFF.However, there is no need to go to the trouble of preparing a separate power supply. A minimum power supply circuit can be easily realized with the circuit shown in FIG. 3. That is, when the switch S is turned on, the output voltage of the variable power supply is output as is. Switch S is OFF''
Sometimes the resistor R acts as a trossover, and by setting the value of R to an appropriate value, minimum power can be easily guaranteed.

Moreover, as mentioned above, fluctuations in the power supply voltage have no dependence on temperature measurement.

FIG. 4 shows an example of a temperature waveform obtained by measuring the temperature of a heating resistor of a thermal head of a multi-gradation thermal transfer printer using the circuit shown in FIG. In the figure, waveform B is thermal navel 1-
The waveform of the applied voltage that drives the is shown, with the vertical axis representing the applied voltage and the horizontal axis representing time.

Waveform A has 411 degrees on the vertical axis and the time on the horizontal scale and the horizontal axis to the waveform on the horizontal axis, and shows the state of temperature that changes in response to the applied voltage LJ at each timing to the waveform.

〔Effect of the invention〕

As described above in detail, according to the temperature measurement method of the present invention, the temperature of the heating resistor in response to the drive signal of an arbitrary drive waveform can be measured with high accuracy, high speed, and without contacting the heating resistor. It can be measured at low cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the temperature measurement method of the present invention, Fig. 2 is an example of the power supply circuit 1-8 used in the C-saiki invention, and Fig. 3 is an example of the power supply circuit using the third embodiment of the power supply circuit of Fig. 2. FIG. 4 is a circuit diagram of the temperature measurement method. FIG. 4 shows an actual measurement example of the temperature waveform of a thermal head using the temperature measurement method of the present invention. FIG. 5 shows a conventional measurement circuit for a heating resistor. In the figure, 1 is a driving power supply, 2 is a divider, 3 is a variable power supply, 4 is a fixed power supply, Rh is a heating resistor, Rs is a detection resistor,
(2) indicates the detection voltage, and ν0 indicates the reference voltage, respectively. Sword ζ Figure 3 Figure 5

Claims (2)

[Claims] (1) In the method of measuring the temperature by detecting the resistance value of the heating resistor, there is provided a means for maintaining the electric power applied to the heating resistor at a predetermined minute power or more, and means for detecting a change in voltage or current appearing in the heating resistor; means for detecting a change based only on the change in the applied power included in the detected value; A temperature measurement method characterized by comprising a calculation means for calculating a temperature change of a heating resistor. (2) The temperature measurement method according to claim 1, wherein the calculation means is constituted by a divider.