JPH032532A - Resistance bulb circuit - Google Patents

Abstract

PURPOSE:To simplify a circuit constitution and to improve the accuracy by providing a noninverting amplifier between conductors which do not include a resistance bulb, connecting a constant current circuit to the output terminal of a conductor including the resistance bulb, and regarding the potential difference between the output terminal of the conductor including the resistance bulb and the output terminal of the amplifier as an output voltage value. CONSTITUTION:The constant current circuit is connected to the output terminal A of the conductor l1 including the resistance bulb Rtd and the noninverting amplifier with a two-fold gain which amplifies a voltage drup e1 generated by one conductor resistance (r) is provided between the two conductors l2 and l3 which do not include the resistance bulb Rtd. The potential difference e0 between the output terminal A of the conductor l1 of the resistance bulb Rtd and the output terminal of the amplifier is led out as a signal which is proportional to variation in the resistance value of the resistance bulb Rtd with temperature. Consequently, the resistance bulb circuit of simple circuit constitution which takes a stable temperature measurement is obtained.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to a resistance temperature detector circuit that detects temperature using a resistance temperature detector whose resistance value changes with temperature changes. Regarding.

(Prior Art) As a conventional three-wire resistance temperature detector circuit, one having the configuration shown in FIG. 4 is known. This conventional resistance temperature detector circuit is
Three conductor wires 1 with equal resistance values rl+r2+r3
A resistance temperature detector R1d whose resistance value changes in proportion to temperature change is connected to the 1st conductor 1, 1°, and 13, and the output terminals A and C of these conductors 1I+13 are connected to a bridge circuit. 11°11 (II-12) is connected to each terminal through which a constant current 11°11 (II-12) flows, and the terminal B of the remaining conductor 12 that does not include the resistance temperature detectors R and d is connected to the high voltage side of VB of the bridge circuit. It has become. Note that the resistor R8 is the output voltage e of the bridge circuit. This is provided in order to provide an OV output at the 0% temperature of the resistance temperature detector R1d.

In this conventional resistance temperature detector circuit, the output voltage is O in the normal state.
V, and when a temperature change occurs, the resistance value of the temperature measuring resistor R1d changes, a voltage drop occurs at the + side terminal of the bridge circuit, and the output voltage e. As a result, an output proportional to the change in resistance value can be obtained.

(Problem to be solved by the invention) However, in such a conventional resistance temperature detector circuit,
It is necessary to always make the current at both ends of the bridge circuit equal, and for this purpose two systems of constant current circuits I, I2 are required, and since the circuit configuration of this constant current circuit is generally complex, The overall configuration of the resistance temperature detector circuit is complicated, and it is technically difficult to simultaneously maintain constant currents of two systems at a constant precision.

This invention was made in view of these conventional problems, and allows stable temperature measurement without being affected by the conductor resistance of a 3-wire resistance thermometer with a simple circuit configuration using a single constant current circuit. The purpose of the present invention is to provide a 1111 temperature resistor circuit that can perform the following steps.

[Configuration of the Invention (Means for Solving the Problems)] The resistance temperature detector circuit of the present invention connects the constant current circuit 11 to the output end A of the conductor 11 including the resistance temperature detector R1d, and A non-inverting amplifier with a gain of 2 to amplify the voltage drop e caused by the resistance r of one conductor is provided between the output terminals B and C of the two conductors 1213 that do not include the resistance temperature detector R.
The potential difference e between the output A of the conductor 11 and the output of the amplifier, including +d. is extracted as a signal proportional to the change in resistance value due to temperature of the temperature measuring resistor R-.

(Function) In the resistance temperature detector circuit of the present invention, the voltage drop el (-1+ ・r) caused by one conductor resistance r due to the constant current 1 from the constant current circuit is reduced to 2e+ by an amplifier with a gain of 2.
A voltage of 2e+ is applied to the output terminal.

Then, at the output end of the conductor 11 including the resistance temperature detector Rld, a constant current .function.
, flows, so as voltage e2, e2 = eH+
l ((r +R+++) is obtained, and the output voltage e is: eo-e2 2e+ = [11' rl rl (r+Rz+→
]2 (■ 1 ・ “ ) = 1 + ” R, d.

Therefore, as the resistance temperature detector R1d, its resistance value R at 0% is
8, and if the change in resistance value is ΔR-, then the above output voltage e. is, eo = l, (Ro + ΔRy) - I,
−ΔR+++I + ”Ro.

Therefore, since the second term in this equation, 11.Ro, is a constant term, this value is used as a bias beforehand to set the output voltage e.

Either build a circuit to subtract it from the output voltage e
. By performing subtraction processing in the next stage of processing, it is possible to obtain a temperature detection signal as an output voltage signal proportional to the change in resistance value of the resistance temperature sensor.

(Example) Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 shows the circuit configuration of an embodiment of the present invention.
Equal conductor resistance r+ 1 as a 3-wire resistance temperature detector circuit
21 '3 (""r) conductor II with each
A conductive wire 1.I 12+ 13 is provided and includes a resistance temperature detector R+a. The output terminal A serves as a + terminal for the temperature signal, and is connected to a constant current circuit 1 which supplies a constant current from a DC power source vb.

A non-inverting amplifier A with a gain of 2 is connected to the output terminal B of the conductor 12.
, , are connected, and the output terminal of this amplifier A□2 serves as one terminal for the temperature signal of the circuit.

The output terminal C of the conductor l is connected to the OV line via a resistor R8. The resistance value of this resistor R6 is a resistance value equivalent to 0% of the temperature measurement range of the resistance temperature detector R16. For example, if the resistance temperature detector R+ d is Pt1OOΩ@0℃, If you want to measure a range of temperatures,
The resistance value of the resistance temperature detector Rld at 0° C.] 00Ω is the value of R6. This resistor R8 is the same as the resistor R8 of the prior art circuit shown in FIG. 4.

Note that the resistors R, , R2 are resistors for giving a double gain to the amplifier A□9.

Next, the operation of the resistance temperature detector circuit having the above configuration will be explained.

The constant current I from the constant current circuit from the DC power supply vb is connected to terminal A.
Flows from the conductor 11 to the conductor 13 and through the resistor Ro to O■
flow to the line. In addition, non-inverting amplifier A with double gain
Since the human power impedance of mp is extremely high, the conductor 12
It can be assumed that no current flows through.

Therefore, conductor 1. The voltage drop across the conductor resistance r1 is II −
rl, the voltage drop across the resistance temperature sensor R1d is 11R+ds, the voltage drop across the conductor resistance r3 of the conductor 13 is 11·r3, and the resistor R6
Let the voltage drop in amplifier A be 11 ・Ro. , the input voltage e is the output voltage with reference to the 0 ■ line →
-The voltages e2 r e3 at one terminal and one terminal are respectively as follows.

First, amplifier A. The input terminal voltage e1 of is e+ = I+
r3+11 ・Ro −(]), and the ten-terminal voltage e2 is = 1 + ・rl + 1+ ・R++++++−
r3 → −I + ”Ro −(2).Then, one terminal voltage e3 is =2 (1+ ”r 3 +I+ ”Ro
) = 2 e 1
... (3).

Here, the output voltage e. is the difference between the child terminal voltage e2 and the one terminal voltage e3 based on the Ov line, so eo = e2 −e3 = (II ” r+ +I+ ”Rld → −
r, -rs+1. -Ro) 2 (11' r3 +1. "R6)...
(4) It becomes.

Furthermore, since r, = r2 = r3 - r, the above equation (
4) can be simplified as follows.

= (2I, r+I, ・R+54-1
+ -Ro)2 (■ 1 ・ r + I 1 ・
Ro)-I I-R,, -I, -R6 = I I (R, Ro)
-(5) Here, if the resistance RO is set to a value equal to the resistance value of the resistance temperature detector R1d, that is, the output voltage e becomes the 0% ratio output. becomes 0, and when the resistance value of the resistance temperature detector R1d changes by ΔR1,l due to temperature rise, ΔRId=R1
Since d-R6, eo=I, ・ΔR1d ・-(6)
becomes.

Equation (6) derived in this way takes a value as the output voltage eo that is completely unaffected by the conductor resistance 'l+2+'3 and is proportional to the change in resistance value due to temperature of the resistance temperature detector R1d. This shows that things can happen without exception. Therefore, in this embodiment, it is possible to obtain a voltage value proportional to temperature change using only one constant current circuit, and careful consideration is given to current accuracy when using two constant current circuits as in the conventional example. This means that temperature can be measured with high accuracy without paying for it.

FIG. 2 shows another embodiment of the present invention, in which the resistor R6 in the embodiment shown in FIG.
. A bias circuit is connected between output terminals C and OV of conductor 13 to give
This is an example in which it is provided between the line.

In this example, the voltage e2 at the child terminal is e 2 =1. (r, +R+d+r3)
+V.

−I ) (2r + Rt d) +V
.

=21+ ” r + 11 s R,,
+vo +++ (7). Further, the voltage e3 at one terminal is e 3 =2e.

=2 (1+ ・r3 +vo)=2 (1,
"r+Vo) =21+・r+2V.

... (8) It is.

Therefore, the output voltage e. teeth eo = e2 -63 =21+−r+I,,R,,+v.

21 + 2 V O =1. -R, -V, -(9).

In this equation (9), the DC bias V. is constant current 1
Since the voltage drop when 1 flows through the resistor R8 is set to be equal to the voltage drop 11 ・Ro, Vo ''' I +
'R.

and eo = I 1’ Rtd V.

-I 1” Rld l +” R.

= ■, (Rtd-RO).

This output voltage e. is the same as the result of equation (6) in the embodiment shown in FIG. 1, and therefore, as shown in equation (7) in the embodiment shown in FIG. The temperature signal can be extracted as a voltage value proportional to the resistance change ΔR-.

In the embodiment shown in FIG. 2, the DC bias V. was installed between the output terminal C and the 0■ line, but
Amplifier A. It is also possible to insert the resistor R2 between the resistor R2 and the OV line with opposite polarity.

FIG. 3 shows still another embodiment of the present invention.
This is a circuit configuration in which the resistor R8 for applying a DC bias is omitted from the circuit configuration shown in FIG.

In this example, the child terminal voltage e2 of the A terminal is e2-=1+' (r, +RId+r
3)=211φr+11·R, and the input voltage e,- of amplifier A1 is e=1.
・Since r3=I, fist r, amplifier A0. The terminal voltage e3- which is the output terminal of is C3=2e, =21+·r. Therefore, the output voltage e. - is e Ol++
e 2 − e 3-2 11 ” r +
11 “Rld 2 It” r=1
．．・It becomes R.

This is the output voltage e. ' indicates a voltage value proportional to the absolute resistance value of the resistance temperature sensor or a measured temperature signal.

Therefore, since R, d - Ro + ΔR1d, e of "1. is, eo-=11 (R,→-△R,d)=I+
-Ro +r, -ΔR111.

Here, ■,・Ro = C (constant), so eo =
I, ·ΔR,, + C ] 2 , and the output voltage value e is set in advance. ′ constant value C
If you subtract , then e o −e o −C −(I 11 ΔR+d+c) −c= 1 ・
ΔR, and the same temperature measurement signal as in each of the embodiments shown in FIGS. 1 and 2 can be extracted as a voltage value.

[Effects of the Invention] As described above, according to the present invention, a non-inverting amplifier with a gain of twice the voltage drop of one conductive wire resistance is provided between the conductive wires that do not include a resistance temperature detector, and the resistance temperature detector is Connect a constant current circuit to the output terminal of the conductor that contains the body and the conductor that does not contain it, and calculate the potential difference between the output terminal of the conductor that contains the body and the output terminal of the amplifier. Since the output voltage value is the output voltage, the voltage value proportional to the change in resistance value caused by the temperature change of the resistance temperature sensor can be extracted as the temperature measurement signal, eliminating the need for two constant current circuits as in the past. , 1. Temperature measurement can be performed using a single constant current circuit, simplifying the circuit configuration and improving accuracy.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of one embodiment of this invention, FIG. 2 is a circuit diagram of another embodiment of this invention, FIG. 3 is a circuit diagram of still another embodiment of this invention, and FIG. 4 is a conventional circuit diagram. FIG. 3 is an example circuit diagram. 1+, 12.13...Conductor 'I+'2+'3...Conductor resistance 11...Constant current circuit A1...Amplifier eO+ eO-...Output voltage R1,...Resistance temperature sensor R6...Resistor Vo・-DC HIAS

Claims (1)

[Claims] In a resistance thermometer circuit that passes current through a 3-wire resistance thermometer and converts the change in resistance value of the resistance temperature sensor due to temperature into voltage, a constant current circuit is installed at the output end of the conductor containing the resistance thermometer. A non-inverting amplifier with a gain of 2 to amplify the voltage drop caused by the resistance of one wire is provided between the output ends of the two conductive wires that do not include the resistance temperature detector, and the conductive wire that includes the resistance temperature detector is provided. A resistance temperature detector circuit configured to extract a potential difference between an output terminal of the amplifier and an output terminal of the amplifier as a signal proportional to a change in resistance value due to temperature of the resistance temperature detector.