JPS61130879A - Resistance measuring apparatus - Google Patents

Abstract

PURPOSE:To simplify the construction, by providing a driver at one end of sensor resistances in measuring resistors to supply current while a common zero suppression resistance is connected to the other end thereof to reduce the number of required drivers and zero suppression resistances to only one. CONSTITUTION:This measuring apparatus is made up of temperature measuring resistors 11, 12 and 1n respectively having sensor resistances Rt1, Tt2...Rtn and wiring resistances ra1, ra2 and ra3, a driver 20 comprising an operational amplifier OP1, first, second and third multiplexers MX1, MX2 and MX3, a zero suppression resistance Ro and a signal processing circuit 5. When the multiplexers MX1, MX2 and MX3 select the temperature measuring resistor 11, current (i) from the driver 20 flows through a series circuit comprising the wiring resistance ra1, the sensor resistance Rt1, a wiring resistance rb1 and the zero suppression resistance Ro to be controlled to a constant value. This makes the output voltage eo of the signal processing circuit 5 free from the effect of the wiring resistance ra1 and rb1 thereby simplifying the construction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a resistance measuring device that measures resistance by sequentially inputting signals from a plurality of resistance temperature sensors.

(Prior Art) FIG. 2 is a connection diagram of a conventional device for measuring the resistance value of a resistance temperature detector, and only one resistance temperature detector is shown here. In the figure, 1 is a resistance temperature sensor, 2 is an input channel section provided corresponding to each resistance temperature sensor 1, 3 is a multiplexer switch for selecting each input channel section, and 4 is a multiplexer switch for selecting each input channel section.
Reference numeral 5 indicates an analog path through which the analog signal selected by the multiplexer switch 3 is transmitted, and 5 indicates a signal processing unit common to each channel that performs arithmetic processing on the signal transmitted via the analog bus 4.

In the input channel unit 2, reference numerals 21 and 22 are self-regulatory constant current circuits that supply constant currents iA and iB in parallel to the input terminals 11 and 12 of the resistance temperature detector 10.

23 is a zero suppression resistor, for example IA =
When iB = 2.5 mA and platinum 100Ω (atO℃) is used as the resistance temperature detector 1, this resistance 23 is 1
000, and the transmission signal is set at 0℃1mv/℃.

The signal processing circuit 5 receives the signal 6H of the analog bus 4.

The resistance value Rt of the temperature sensing resistor 1 is obtained without being affected by wiring resistance etc. by manually performing eL and performing the arithmetic process eH-eL.

(Problems to be Solved by the Invention) The conventional device f with such a configuration requires two constant current circuits for each channel section, and also requires the zero suppression resistor 23 to be connected to each temperature measuring circuit. There is a problem in that it needs to be connected to a resistor, making the overall configuration complicated.

The present invention has been made in view of the above-mentioned problems in conventional devices.The purpose of the present invention is to reduce the number of constant current circuits and zero subledger resistors to one in total, thereby achieving a uniform configuration. , and the shadow of resistance value change of wiring resistance! This is an attempt to realize a resistance measurement pole that does not receive #.

(Tth means for solving the problem) The first multiplexer and the Senna resistance of each resistance temperature sensor (
A wiring resistance (ra) and the first
a driver that supplies current through a multiplexer of
A wiring resistor (
one zero-suppression resistor (Ro) commonly connected through one zero-suppression resistor (Ro), a circuit means for negative feedback of the voltage generated across the zero-suppression resistor to the driver, and one zero-suppression resistor (Ro) connected in common via a second multiplexer that sequentially selects and extracts the voltage of each series circuit consisting of a wiring resistance (rb), a wiring resistance (rb), and a zero subregion resistance (Ro) in synchronization with the first multiplexer; a fifth multiplexer that sequentially selects and extracts the voltage generated in the zero suppression resistor in synchronization with the first multiplexer; a voltage signal sH extracted by the second multiplexer; and a voltage signal eL extracted by the sixth multiplexer. and at least (a
The sensor is characterized by comprising a signal processing circuit that performs signal processing including the calculation H-2.eL) and outputs a signal related to the resistance value of each sensor resistor (Rt).

(Example) FIG. 1 is a configuration and connection diagram showing an example of a device according to the present invention. In the figure, 11.12. . . . 1n are all resistance temperature detectors, and each is installed at a location where the temperature is to be measured. In each of these resistance temperature sensors, Rtl, Rt
2- Rtn is the senna resistance, ral * ra2
-ran+ rbl, rb2°°°rbn, rc
1 and rc2+-rCn both indicate wiring resistance. 20 is each sensor resistor Rt1. Rt2...Rtn
A first multiplexer 'MDCj and wiring resistances ra1. ra2. ...through ran′
A driver that supplies MIc current, here an operational amplifier O to which a reference voltage Vl''e f is applied to one input terminal ←)
Consists of PI. Note that the first multiplexer M
X1 is a wiring resistance r'Lr that sequentially connects the output terminal of the driver 20.
a2...Connected to one end of ran. RO is connected to the other end of each sensor resistor by a wiring resistor rb1. rb2...
rbn tl - a common zero suppression resistor connected through. The voltage ef generated at this zero suppression resistor RO is
) has been given negative feedback. MX2 is the second multiplexer, which has wiring resistance ra, connection resistance Rt, and wiring resistance rb.
and zero sagre7. The voltages eH1, aH2, .

MX3 is a third multiplexer, which outputs voltages eL1. eL2...eLn are selected and taken out in synchronization with the first multiplexer MX1. 5
is a signal processing circuit that combines the voltage signal eH taken out by the second multiplexer MX2, the voltage signal eL taken out by the third multiplexer MX3, and at least eH
-2・eL performance 31. For all rows, each sensor resistance Rt
A signal e0 related to the resistance values of l, Rt2, . . . Rtn is output. This signal processing circuit 5 is as follows.
It consists of an operational amplifier op2.

The operation of the apparatus configured in this way will be explained next.

1st. 26th each third multiplexer MX1, MX
2.

MX3 all operate synchronously, and resistance temperature detectors 11, 12. . . . ln are selected in sequence.

Now, each ff / L / f plexi length MX1, MX2
, MX3 selects the resistance temperature detector 11, the current i from the driver 20 is the wiring resistance ra1 of the resistance temperature detector 1, the sensor resistance Rti, and the wiring resistance rb.
1 and a zero suppression resistor Ro. At this time, a voltage eHi f expressed by equation (1) is generated across the series circuit including the sensor resistor Rti.

eHl = (ra1+Rt1+rb1+Ro) ・i
-・” (11 In addition, i4 is connected to both ends of the series circuit consisting of wiring resistance rb1 and zero suppression resistance RO,
A voltage eL1 expressed by the formula +21 is generated.

eLl = (rbl + Ro) ・i
...(21 Also, zero suppression resistance R
, a rolling pressure ef expressed by equation (3) is generated at both ends of .

e f = Ro−i
--(31) The voltage ef expressed by equation (3) is negatively fed back to the driver 20, and the driver 20 controls the output DC i so that ef=Vref. Therefore, the output current 1 is , (4), and is maintained at a constant value of 1 corresponding to the reference voltage Vref.

・Vr@f・・・・・・(
4)O The common signal processing circuit 5 is connected to the second. Third multiplexer MX2. Input the voltage signals eH1 and eLl' expressed by the +11 formula and (21 formula) through the MX3, and (
5) Perform the calculation shown in the formula to obtain the output voltage e. Get all.

e = eHl −2・eLl
・・・・・・(5) ■ = (ral + Rtl −rbl +Ro) ・
12frb1+Ro)·t In equation (5), if wiring resistance ra1=rb1, equation (5) becomes equation (6).

e = (Rtl-Ro) ・i
--tel Therefore, the output voltage e μ of the signal processing circuit 5,
Under the influence of the wiring resistances ra1, rbl, etc., the value corresponds to the value of the sensor resistance Rt1.

Below, Part 1. Second. Third multiplexer MX1゜MX
2. By MX3, each resistance temperature sensor 12...1n
By selecting similarly, each sensor resistance Rt2・
...Rtn f each wiring resistance ra2...ran, rb
2...The influence of rbn can be measured without any damage.

In the above embodiment, the signal processing circuit 5 is constructed of an operational amplifier, but it may be constructed of other circuits, such as a digital circuit including an A/D converter, a microprocessor, and the like.

(Effects of the Invention) As explained above, according to the present invention, only one driver and one zero suppression resistor are required, so the configuration is simple and the resistance is not affected by the wiring resistance to each resistance temperature detector. A measuring device can be realized.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of the device of the present invention, and FIG. 2 is a connection diagram of a conventional device.

Claims (1)

[Claims] The first multiplexer and the sensor resistance (
A wiring resistance (ra) and the first
a driver that supplies current through a multiplexer of
A wiring resistor (
one zero-suppression resistor (Ro) commonly connected through one zero-suppression resistor (Ro), a circuit means for negative feedback of the voltage generated in this zero-suppression resistor to the driver, the wiring resistor (RA), and the sensor resistor (Rt). , wiring resistance (
a second multiplexer that sequentially selects and extracts the voltage of each series circuit consisting of the wiring resistance rb) and the zero suppression resistor (Ro) in synchronization with the first multiplexer; A third multiplexer that sequentially selects and extracts data in synchronization with the first multiplexer, a voltage signal eH extracted by the second multiplexer, and a voltage signal eL extracted by the third multiplexer are input, and at least (eH -2
- A resistance measuring device equipped with a signal processing circuit that performs signal processing including calculations such as eL) and outputs a signal related to the resistance value of each sensor resistor (Rt).