JP3170084B2 - Temperature measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring device using a resistance temperature detector as a temperature detecting sensor.

[0002]

2. Description of the Related Art As a conventional temperature measuring device, for example, there is one as shown in FIG. In the figure, reference numeral 8 denotes a resistance thermometer for temperature detection, 9 denotes a measurement line for measuring a line resistance up to the resistance thermometer 8, and these resistance thermometers 8 and the measurement line 9 are connected to each other. On the other hand, a first constant current source 3 and a second constant current source 4 for supplying a DC constant current are provided. 1 is a microcomputer, 2 is an A / D converter, and 10 and 11 are adjustment circuits for adjusting the DC constant currents from the first and second constant current sources 3 and 4 to be equal to each other. Then, the respective voltage drops generated in the resistance temperature detector 8 and the measurement line 9 by the respective current supply from the first and second constant current sources 3 and 4 are transmitted to the microcomputer 1 via the A / D converter 2. A resistance value of the resistance temperature detector 8 is obtained from the voltage difference between the two voltage drops, and the temperature is converted to a temperature to measure the temperature. At this time, a measurement error occurs due to a mutual difference between the first and second constant current sources 3 and 4, an environmental (temperature and humidity) change, an aging change, and the like of each constant current source 3 and 4. In addition, high-precision constant current sources 3 and 4 are used, and initial adjustment and periodic adjustment are performed by adjustment circuits 10 and 11.

[0003]

In the conventional temperature measuring device, an initial adjustment and a periodic adjustment are performed by an adjustment circuit for the mutual difference between the first and second constant current sources, environmental change, aging, and the like. ing. Of these, changes over time have been readjusted through periodic tests. For this reason, the adjustment operation is troublesome, and a measurement error occurs if there is an adjustment error.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature measuring device capable of performing accurate temperature measurement without requiring an adjusting circuit.

[0005]

According to the present invention, there is provided a temperature measuring resistor for detecting a temperature, a first current source for supplying a constant current to the temperature measuring resistor, and A second current source for supplying a constant current to a measurement line for measuring a line resistance up to the resistance temperature detector; and a second current source provided corresponding to the first current source and the second current source, respectively. A known resistor for previously checking each constant current value from the first current source and the second current source, and a current from the first current source to the temperature measuring resistor and the known resistor. A switch for switching the current from the second current source to the measurement line and the known resistance, and inputting a voltage drop generated in each of the temperature measuring resistor, the measurement line and the known resistance by energization. A system for determining the resistance value of the resistance bulb and controlling the changeover switch. And summarized in that a means.

[0006]

In the above arrangement, before the temperature is detected by the resistance temperature detector, first, the changeover switch is switched to the known resistance. Then, the currents from the first current source and the second current source are respectively supplied to the known resistors, and the voltage drops are read by the control means, and the constant currents from the first current source and the second current source are read. Current values are determined and those values are stored in advance. Next, the changeover switch is switched to the resistance temperature detector and the measurement line side. Then, the current from the first current source is supplied to the resistance bulb, the current from the second current source is supplied to the measurement line, and the respective voltage drops are read by the control means. The resistance value of the resistance temperature detector is obtained from the current values from the first and second current sources stored beforehand, and the temperature is measured by converting the resistance value into a temperature. Thus, accurate temperature measurement can be performed without the need for an adjustment circuit.

[0007]

An embodiment of the present invention will be described below with reference to FIG. 1 that are the same as or equivalent to the devices and elements in FIG. 2 are denoted by the same reference numerals as those described above, and redundant description will be omitted.

First, the configuration of the temperature measuring device will be described.
In this embodiment, the first constant current source 3 and the second constant current source 4
The precision known resistors 6 and 7 for preliminarily inspecting each of the constant DC constant current values I ₁ and I ₂ are provided corresponding to the first constant current source 3 and the second constant current source 4, respectively. Have been. Further, the current from the first constant current source 3 is switched to the temperature measuring resistor 8 and the precision known resistor 6, and the current from the second constant current source 4 is switched to the measurement line 9 and the precision known resistor 7. A changeover switch 5 is provided. The changeover switch 5 is controlled by a command from the microcomputer 1. Current is passed between the microcomputer 1 and the A / D converter 2, and the resistance temperature detector 8, the measurement line 9, and the known resistances 6, 7
A control means for obtaining the resistance value of the resistance temperature detector 8 by inputting the respective voltage drops occurring in the above-mentioned manner is constituted.

Next, the measuring operation of the temperature measuring device configured as described above will be described. Before temperature detection is performed by the resistance temperature detector 8, the changeover switch 5 is switched to the precision known resistors 6 and 7 so that the currents from the first constant current source 3 and the second constant current source 4 are respectively Power is supplied to the precision known resistors 6 and 7,
The respective DC constant current values I ₁ and I ₂ are obtained and stored in the microcomputer 1. That is, the resistance values of the precision known resistors 6 and 7 are R ₁ (Ω) and R ₂ (Ω), respectively, and the voltages generated when the DC currents I ₁ and I ₂ are applied thereto are V ₁ and V ₂ , respectively. Then, these voltages V ₁ and V ₂ become A /
The data is read into the microcomputer 1 via the D converter 2, and I ₁ = V ₁ / R ₁ and I ₂ = V ₂ / R ₂ are calculated and stored.

Next, the changeover switch 5 is switched to the temperature measuring resistor 8 and the measuring line 9 side, and the DC current I ₁ ,
I ₂ is supplied to the resistance temperature detector 8 and the measurement line 9. Assuming that the voltage generated at the resistance temperature detector 8 at this time is V _r and the voltage generated at the measurement line 9 is V _o , these voltages are A
The resistance value R of the resistance temperature detector 8 is read by the microcomputer 1 via the / D converter 2 and is calculated as follows. That is, the one-way line resistance of the measurement line 9 is _Ro.
(Ω)

[Formula 1] V _r = (R + 2R _o ) · I ₁ and V _o = 2R _o · I ₂ hold. This voltage value V _r, the resistance value R of the resistance temperature detector 8 for temperature conversion from V _o and the DC current value previously stored I _1, I ₂ are obtained.

[0011]

[Number 2] _{R = (V r / I 1} ) -2R o = (V r / I 1)
− (V _o / I ₂ ) In this way, the resistance value R of the resistance temperature detector 8 becomes the first and second resistance values.
Irrespective of the mutual difference between the constant current sources 3 and 4. Therefore, accurate temperature measurement can be performed without the need for an adjustment circuit and its periodic adjustment work.

[0012]

As described above, according to the present invention,
A known resistor that is provided corresponding to the first current source and the second current source, respectively, and that checks a predetermined current value from the first current source and the second current source in advance; The current from the first current source is switched to a resistance temperature detector and a known resistance,
And a changeover switch for switching the current from the current source between the measurement line and the known resistance, and inputting the voltage drop generated in the resistance thermometer, the measurement line and the known resistance due to energization, and inputting the resistance value of the resistance thermometer. And control means for controlling the changeover switch, so that the resistance value of the resistance temperature detector can be accurately obtained irrespective of the difference between the first and second current sources, and an adjustment circuit is required. It is possible to perform accurate temperature measurement without performing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a temperature measuring device according to the present invention.

FIG. 2 is a circuit diagram showing a conventional temperature measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Microcomputer 2 A / D converter which comprises a control means with a microcomputer 3 1st constant current source 4 2nd constant current source 5 Changeover switch 6,7 Precision known resistance 8 Temperature measuring resistor 9 Measurement line

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-52529 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01K 7/18 G01K 7/24

Claims (1)

(57) [Claims] 1. A temperature measuring resistor for detecting a temperature, a first current source for supplying a constant current to the temperature measuring resistor, and a measuring device for measuring a line resistance to the temperature measuring resistor. A second current source for supplying a constant current to the line, and the first current source and the second current source are provided corresponding to the first current source and the second current source, respectively;
A known resistor for previously inspecting each constant current value from the current source and the second current source, and switching the current from the first current source to the temperature measuring resistor and the known resistor, A changeover switch for switching the current from the current source 2 to the measurement line and the known resistance, and inputting voltage drops generated in the temperature measurement resistor, the measurement line, and the known resistance due to energization, and And a control means for determining the resistance value and controlling the changeover switch.