JPH0320633A - Multipoint-signal measuring apparatus - Google Patents

Abstract

PURPOSE:To remove the effects of not only a lead wire resistance but also the ON resistance of a switch and the like and to make it possible to perform high-speed measurement by selectively receiving the signals of a plurality of channels including a DC voltage signal, which are applied to the input terminals of a terminal plate from a temperature resistor and a thermocouple, through the switches of a scanner board. CONSTITUTION:The signals of a plurality of channels including a DC voltage signal Ex are applied to the input terminals of a terminal board A from a measuring resistor Rt and a thermocouple TC. The signals are received by an operating circuit part C selectively through switches SW of a scanner board B. Each terminal voltage of the resistor Rt which is received with the circuit C is received with an operating means selectively. The effect of the resistance of a lead wire and the ON resistance are removed, and the resistance value is operated. The output signal of the thermocouple TC and the signal Ex which are received by the circuit part C are received in an amplifying means selectively through the switches and amplified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a multi-point signal measuring device, and more specifically, to a multi-point signal measuring device. This relates to a device that can selectively switch and measure multiple channels of signals, including thermocouple and DC voltage signals, via a switch. BACKGROUND ART One type of multipoint signal measuring device is a multipoint temperature measuring device configured to selectively switch a plurality of resistance temperature sensors each having three terminals via a switch.

FIG. 4 is a circuit diagram showing an example of such a conventional device. In the figure, Rt is a plurality of resistance temperature sensors having 3@1'a to Tc. a and b are a plurality of first and second switches whose one end is connected to the first terminal Ta of each resistance temperature detector Rt and are selectively driven in conjunction; d is a plurality of switches whose one end is connected to the first terminal Ta of each resistance temperature detector Rt; is connected to the second terminal Tb of the first and second switches a. A plurality of third switches d to g are selectively driven in conjunction with the first and second switches d to g, each of which has one end connected to the third terminal 1c of each resistance temperature detector Rt. A plurality of fourth to seventh switches that are selectively driven in conjunction with the second and third switches a to C.
These fourth to seventh switches d-g
are connected in parallel to reduce on-resistance.

One end of i is connected to the terminal of the first switch a, and fl! !
A constant current source whose end is connected to a common potential point, At is a first operational amplifier, a non-inverting input terminal is connected to the other end of the second switch b, and an inverting input terminal is connected to the input terminal. ing. A2 is a second operational amplifier, whose non-inverting input terminal is connected to the other end of the third switch C, and whose inverting input terminal is connected to the output terminal of the first operational amplifier A1 via a resistor Ra. It is connected to its own output terminal via a resistor Rb. The terminals of the fourth to seventh switches d to g are connected to a common potential point. r indicates the lead wire resistance of the resistance temperature detector Rt. In such a configuration, each of the switches a to g is selectively driven on and off in units of temperature measuring resistance #:Rt.

Here, the output @ current of the constant current source is i, the output voltage of the second switch b is ■ A, the output voltage of the third switch C is VB,
If the parallel on-resistance of the fourth to seventh switches d to g is rc, VA = i(r+Ilt"r+rc)
”II), and VB = i(r+r C )
...(2) It becomes. Therefore, the output voltage E0 of the second operational amplifier A2 is E o = i(Rt-rc)
−(3).

However, according to such a device, although it is not affected by the lead wire resistance r of the resistance temperature detector Rt, the parallel on-resistance of the fourth to seventh switches d to g is The influence of rc cannot be removed. Therefore, relays with low on-resistance are generally used as these switches, but relays are relatively expensive, operate at a relatively slow speed, have a variable parallel on-resistance (r), and have a relatively short lifespan. In addition, with this configuration, highly accurate measurements using a 4-wire resistance thermometer cannot be performed.Furthermore, it is difficult to measure thermocouple output signals, DC voltage signals, etc. It is also not possible to process different types of signals.

The present invention has focused on these points, and its purpose is to selectively switch and capture multiple channels of signals including resistance temperature detectors, thermocouples, and DC voltage signals via a switch. This is a multi-point signal measurement device that can eliminate the effects of lead wire resistance, switch on resistance, and contact resistance of current path connectors when measuring temperature at multiple points by switching multiple resistance thermometers with a switch. The goal is to provide the following. Means for Solving the Problems> The multi-point signal measuring device of the present invention includes a resistance temperature detector. multiple input terminals to which multiple channels of signal lines including thermocouple and DC voltage signals are individually connected;
a terminal board having a connector connected to each input terminal; a first connector connected to the connector of this terminal board;
a scanner board having a plurality of switches connected to the first connector and selectively driven for each channel; a second connector to which the switches are commonly connected; a second connector of the scanner board; a constant current source that selectively supplies current to the resistance temperature detector connected to the terminal board via a switch, and a voltage at each terminal of the resistance temperature detector connected to the terminal board. a calculation means for selectively taking in the signal through the switch and calculating the resistance value of the resistance temperature detector; and an amplifying means for selectively taking in and amplifying the thermocouple and DC voltage signal connected to the terminal board through the switch. It is characterized by having an arithmetic circuit section having the following. Effect> A resistance temperature detector added to the input terminal of the terminal board. Multiple channels of signals, including thermocouple and DC voltage signals, are selectively taken into the arithmetic circuit section via a switch on the scanner board.

The voltage at each terminal of the RTD taken into the calculation circuit section is then selectively taken into the calculation means via the switch, and the influence of the lead wire resistance and the on-resistance of the switch is removed, and the resistance value is calculated. It will be done. Furthermore, the thermocouple output signal and DC voltage signal taken into the arithmetic circuit section are further selectively taken into the amplification means via a switch.
amplified.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals. In the figure, a terminal board A has a plurality of input terminals Ta1 to TCTL to which signal lines of a plurality of channels including a resistance temperature detector Rt, a thermocouple TC, and a DC voltage signal Ex are individually connected, and each input terminal Ta1. A connector CN connected to ~TCTL is provided.

The scanner board B has a first connector CN2 connected to the connector CN of the terminal board A, and a first connector CN2 connected to the connector CN of the terminal board A.
2 and selectively driven for each channel, and each of these switches a1 to e
A second connector CN, to which the TLs are commonly connected, is provided.

In the arithmetic circuit section C, current is selectively supplied to the connector CN a connected to the second connector CN3 of the scanner board B and the resistance temperature detector Rt connected to the terminal board A via the switch SW5. The constant current source i and each terminal voltage VA, VB, V of the resistance temperature detector Rt connected to the terminal plate A
Operational amplifiers A3 to A that selectively take in D via switches SW6 to SW, and calculate the resistance value of the temperature measuring resistor IRt.
5 and a thermocouple connected to the terminal board A.
rC and DC voltage signal Ex through switches SW1 to SW4
Amplifying means is provided which consists of an operational amplifier A6 which selectively takes in and amplifies the signal via the . The output signal of the calculation means is SW. is input to the amplification means via. Specifically, the constant t current source i is connected to the signal line of the switch a system via the switch SW5. Operational amplifier A
The non-inverting input terminal of , is connected to the signal line of the switch b system via switch SW6, and the inverting input terminal is connected to the output terminal via resistor R2 and to one end of resistor R3 via resistor R, has been done. The non-inverting input terminal of the operational amplifier A4 is connected to the signal line of the switch d system via the switch SW8, and the inverting input terminal is connected to the signal line of the switch d system via the resistor R4.
It is connected to the output terminal and to one end of the resistor R via the resistor R3. Resistors Rl and U (anti-R3
The connection point of is connected to the common potential point via a resistor Rc, and is also connected to the signal line of the switch system e via a switch SW9. Note that the resistor Rc is for making the output voltage Ov at 0°C, and if a platinum resistance thermometer having a resistance value of 100Ω at 0°C is used as the resistance temperature detector Rt, the resistor Rc is set to 100Ω. Connecting. Ellipsis amplifier A! The non-inverting input terminal of l is connected to the signal line of switch d system and to the common potential point via switch SW7, and the inverting input terminal is connected to the output terminal via resistor R7 and via resistor R5. is connected to the output terminal of operational amplifier A3, and further connected to the output terminal of operational amplifier A4 via resistor R6. switch b
The signal line of the system includes a first series circuit in which switch SW, resistor R8, and switch SW2 are connected in series, and switch SW3 and resistors Rg, R, . voltage divider circuit and switch SW,
I is connected in series to the non-inverting input terminal of operational amplifier A6 via a second series circuit connected in parallel with the first series circuit. The inverting input terminal of the operational amplifier A6 is connected to the output terminal via a resistor R, ., and is also connected to a common potential point via a resistor R12. The operations of the device configured in this way can be roughly divided into three: (1) measurement using the resistance temperature detector Rt, (2) measurement of the thermocouple TC or DC voltage signal Ex, and (2) calibration operation of OmV inside the device. Each operation will be explained below. In addition, each switch a1 to e of scanner board B
The TL is selectively turned on and off for each measurement channel. (2) Measurement using resistance temperature detector Rt For measurement using resistance temperature detector Rt, switches SW, -SW4 and SW7 of the arithmetic circuit section C are turned off, sw, , sw, and SW, -SW,. Turn on. As a result, the output current of constant current source i is changed to switch S
It flows to the common potential point through W5, switch a, lead wire resistance r of terminal Ta (Ii!I, temperature measuring resistor Rt, lead wire resistance r on terminal Tc side, switch e, switch SW, and resistor Rc). Here, the output current of the constant current source is i, the voltage of the signal line of switch b system is ■^, the voltage of the signal line of switch C system is VB, the voltage of the signal line of switch d system is Vo, switch SW. VC is the voltage at the connection point between 5l and resistor Rc, and RS is the sum of the on-resistances of switch e and SW9.
Then, VA = ifr + Rt + r + fls) + Vc, V day = i (r +, VO =, Rs) + Vc ・ Rs + l + fc ... (4) ... (5) ... (6). From the above formula, the output voltage Ea of operational amplifier A3...(
8) Then, the operational amplifier A. The output voltage Eb of the operational amplifier A5 becomes, the input voltage Ec of the non-inverting input terminal of the operational amplifier A5-/) becomes ... oO, and the output voltage Eo of the operational amplifier A5 becomes ... (
11) It becomes. From this equation (11), by determining the resistances R and ~R7 so as to eliminate the term Rs, the sum of the lead wire resistance r, the switch e, and the on-resistance of SW9, Eo=- + (Rt-Rc )
...(12) is obtained. Note that the resistance values of these resistors R, to R7 are, for example, R, =R. 3=9.8KΩ, R2=R4=R5-
几. = 10KΩ, and R7 = 5KΩ. The output signal Eo of the operational amplifier A5 is applied to the operational amplifier A6 via the switch SW,o, and is applied to the operational amplifier A6 through the resistor Rl! ．．
It is amplified and output according to the gain set by R12. ■Measurement of thermocouple 'I' C or DC voltage signal Ex.
Switches sw, , sw6 and SW s to SW + o related to the calculation means for the resistance value of are turned off. If voltage division is not required depending on the magnitude of the input signal, switches sw, , sw2 are turned on and switches sw. , sw. is turned off. As a result, the voltage vA of the signal line of the switch b system is applied to the operational amplifier A6 via the series circuit of the switch SW, the resistor R8, and the switch SW2. On the other hand, if voltage division is required, switch SW1. Turn off sw2 and switch SW,,SW,
Turn on. As a result, the voltage VA of the signal line of the switch b system is applied to the operational amplifier A6 by the switch SW, the resistors R9 and R, and the voltage VA of the signal line of the switch b system. It is applied via the voltage divider circuit and the series circuit of switch SW4. (2) Calibration operation of OmV inside the device For internal calibration, use the switches sw, ~sw,. Turn on SW4 and SW7 and turn off the other switches. As a result, the input terminal of the operational amplifier A6 is connected to the on-resistance of the switch SW4 and the resistor R. Since the input terminal Ta of the terminal board A is connected to the common potential point via the common potential point, the conditions are substantially equal to the conditions for performing calibration by connecting the input terminal Ta of the terminal board A to the common potential point, and highly accurate calibration can be performed.

The on/off control of the switches SW1 to SW+o of the arithmetic circuit section C and the switching control of the switches a to eTL of the scanner board B in each operation mode are electronically performed by a control means such as a microprocessor (not shown). be able to. With this configuration, the resistance temperature detector Rt. It is possible to measure and process the signals of multiple channels including the multi-voltage coupler TC and the DC voltage signal qVx with a common calculation port, and also to measure the temperature at multiple points by switching the multiple resistance temperature detectors Rt with a switch. In this case, the effects of lead wire resistance, on-resistance of the switch, and contact resistance of the connector in the current path can be eliminated. In addition, with this configuration, semiconductor switches with high on-resistance but high reliability and high-speed switching operation can be used as each switch, and high-speed measurement can be achieved compared to the case of using RH contacts. This increases the reliability of the entire device. FIG. 2 shows the arithmetic circuit section C of FIG. 1 with an automatic calibration circuit for the resistance temperature detector Rt added. That is, the non-inverting input terminal of the operational amplifier A4 and the connection point between the resistors RC and R3 are connected via the switch SW++. Reference resistance R
One end of R (generally 100Ω) is connected to the output terminal of constant current source i via switch SW, 2, and is also connected to the non-inverting input terminal of operational amplifier A3 via switch SW, 3. It is connected to the connection point between the resistors Rc and R3, and is also connected to the non-inverting input terminal of the operational amplifier A3 via the switch SW,4.
The non-inverting input terminal 5 is connected to the connection point between the resistors Rc and R3 and the signal line of the switch C system via the changeover switch SW, 5.

In such a configuration, in addition to the three measurement functions (■ to ■) shown in FIG. Each measurement operation will be explained.

■Measurement using the resistance temperature detector Rt For the measurement using the resistance temperature detector Rt in Fig. 2, the switches SW1 to SW4, S of the arithmetic circuit section C are
W7, SW,. , turn off SVI'+2, sw5
, sw, and SW8 to SW,. Turn on the movable contacts of switches SW, 3 to SW, and 5 to b ft.
Switch to lj. As a result, the resistance temperature detector R in FIG.
The same conditions as in the measurement using t will be set. ■ Measurement of thermocouple T C or DC voltage signal Ex and ■
Calibration of ○mV inside the device can be performed using the same switch settings as shown in Figure 1. ■0Ω Calibration Operation For 0Ω calibration, turn off switches SW, to SW9, and then switch SW. ~Turn on SW, 2, switch the movable contact of switch SW, 3 to b III,
Switch SW+ 4.3W+ Switch the movable contact of 5 to APL. As a result, the output current of the constant current source i flows to the common potential point through the switch SW12, the base resistor RR, and the resistor Rc. The voltage Vc at the connection point of the resistors Rc and R3 is applied to the non-inverting input terminal of the operational amplifier A3 via the switch SW, 5, and the voltage Vc at the connection point of the resistors Rc and R3 is applied to the non-inverting input terminal of the operational amplifier A5 via the switch SW, 5. Resistance Rc and R
The voltage Vc at the connection point 3 is applied, and 0Ω calibration is performed. ■100Ω calibration operation For 100Ω calibration, start from the 0Ω calibration state, leave switches SW, ~SW, 2 as they are, and switch SW,
3, SW+5 movable contact a III! I, and switch SW+ and the movable contact of I according to the b{ rule. As a result, the switch SW. , the voltage at the connection point between the switch SW,2 and the reference resistor RR is applied to the non-inverting input terminal of the operational amplifier A5, and the voltage Vc at the connection point between the resistors Rc and R3 is applied to the non-inverting input terminal of the operational amplifier A5 via the switch SW,5. 10
0Ω calibration is performed. FIG. 3 is an explanatory diagram when measuring a four-wire resistance temperature detector using the arithmetic circuit section C in FIGS. 1 and 2. FIG. In this case, the terminal board A is provided with four terminals 1'a to Td and a connector CNI for each channel, and the scanner board B is a connector that is fitted and connected to the connector CNI of the terminal board A. CN2, four switches a to d provided for each channel, and a connector CN3 to which the switches a to d of each channel are commonly connected and are fitted and connected to the connector CN4 of the arithmetic circuit section C;
Use one with a As a result, the resistance temperature detector R
A current terminal and a voltage terminal are provided at both ends of t, allowing for more accurate measurements than in the case of three terminals. Further, although the embodiment shown in FIG. 1 shows an example of an insulation switching type in which each terminal of the three-terminal resistance temperature detector Rt is switched at the same time, the system of terminals Tc may be a non-insulation type without switching. By making this non-insulated type, scanner board B
can reduce costs by reducing the number of switches required.

As explained above, according to the present invention, not only the lead wire resistance but also the on-resistance of the switch and the contact resistance of the connector of the current path can be eliminated, and the reliability of high-distance measurement can be improved. A multi-point signal measurement device with high performance can be realized.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figures 2 and 3 are
The figures are circuit diagrams showing other embodiments of the present invention, and FIG. 4 is a circuit diagram showing an example of a conventional device. Rt...Resistance temperature sensor, i...Constant current source, a~e...
・Switch, A ~ A6... Calculation m @ device, R. c. R
, ~RI2...Resistance, RR...Reference resistance, SW
+~SWI5...Switch, A...Terminal board, B...
・Scanner board, Fig. 3 Textbook board, Fig. 4 (rc)

Claims (1)

[Claims] A plurality of input terminals to which signal lines of a plurality of channels including a resistance temperature detector, a thermocouple, and a DC voltage signal are individually connected;
a terminal board having a connector connected to each input terminal; a first connector connected to the connector of this terminal board;
a scanner board having a plurality of switches connected to the first connector and selectively driven for each channel; a second connector to which the switches are commonly connected; a second connector of the scanner board; a constant current source that selectively supplies current to the resistance temperature detector connected to the terminal board via a switch, and a voltage at each terminal of the resistance temperature detector connected to the terminal board. a calculation means for selectively taking in the signal through the switch and calculating the resistance value of the resistance temperature detector; and an amplifying means for selectively taking in and amplifying the thermocouple and DC voltage signal connected to the terminal board through the switch. A multi-point signal measuring device comprising: an arithmetic circuit section having the following features: