CA1107832A - Multipoint measuring device - Google Patents
Multipoint measuring deviceInfo
- Publication number
- CA1107832A CA1107832A CA301,644A CA301644A CA1107832A CA 1107832 A CA1107832 A CA 1107832A CA 301644 A CA301644 A CA 301644A CA 1107832 A CA1107832 A CA 1107832A
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- Prior art keywords
- bridge network
- measuring
- compensator
- transducers
- selector switch
- Prior art date
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Abstract
MULTIPOINT MEASURING DEVICE
Abstract of the Disclosure A multipoint measuring device is based on a measur-ing bridge network and uses transducers which convert the quantity under measurement into an electrical signal, the transducers being divided into two identical groups, and being connected via a selector switch and main and auxiliary compensators in one or two adjacent arms of the measuring bridge network. With the transducers connected in two adjacent arms of the measuring bridge network, each transducer group is connected only in a single arm via its respective main compen-sator and its respective auxiliary compensator and the con-nection point of two auxiliary compensators is used as a measurement point of a measuring diagonal of the measuring bridge network. With the transducers connected in a single arm of the measuring bridge network, each transducer group is connected alternately in a respective arm via its respect-ive main compensator and its respective auxiliary compensator, while only a respective auxiliary compensator is connected to the measurement point of the measuring diagonal of the measur-ing bridge network.
Abstract of the Disclosure A multipoint measuring device is based on a measur-ing bridge network and uses transducers which convert the quantity under measurement into an electrical signal, the transducers being divided into two identical groups, and being connected via a selector switch and main and auxiliary compensators in one or two adjacent arms of the measuring bridge network. With the transducers connected in two adjacent arms of the measuring bridge network, each transducer group is connected only in a single arm via its respective main compen-sator and its respective auxiliary compensator and the con-nection point of two auxiliary compensators is used as a measurement point of a measuring diagonal of the measuring bridge network. With the transducers connected in a single arm of the measuring bridge network, each transducer group is connected alternately in a respective arm via its respect-ive main compensator and its respective auxiliary compensator, while only a respective auxiliary compensator is connected to the measurement point of the measuring diagonal of the measur-ing bridge network.
Description
1~)7~2 The invention relates to electrical measuring devices, and, more particularly, to multipoint measuring devices. It is suitable for conducting multipoint measure-ments concerned with very diverse fields of industry and performed with the help of strain gauges and resistance thermometers. The invention is especially suitable for strength tests performed on commercial articles.
Known in the art is a measuring device using a measuring bridge network the supply diagonal of which accepts a sine-wave or a d,c. supply voltage, Suply voltages taken from a power supply are delivered over a lead via two voltage regulators to a half-bridge network comprised of two series~
connected transducers (cf. Auslegeschrift No. 2,314,754, FRG), Such a circuit can utilize a single transducer if the adjacent arm of the circuit is provided with a compensating transducer or an auxiliary resistor. The known multipoint measuring device is inoperative if a single transducer is incorporated therein so that no compensating transducer or auxiliary resistor is used. The measurement points of a measuring diagonal of the known device, which are provided when the two transducers connect each other or a single transducer connects the compensating transducer of the auxiliary resistor, are combined using a common bus. This feature makes the known device inoperative if either of the transducers is accidentally connected to the ground bus.
Moreover, the known device can use transducers of identical characteristics with the result that a limited number of uses is possible in the case of multipoint measurements.
Although the known device provides for the transfer of the potential produced by the power supply without distortion, it is unable to resist the effect of the impedance of the leads between the common buses of the measurement points and the device subassemblies, as well as the effect of the ~;J
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contact resistances and their changes in the circuit resulting from the action of temperature, humidity and other disturb-ing factors. It is especially important to eliminate these harmful effects when small quantities are to be measured.
An object of the invention is to provide a multi-point measuring device which can be operated without troubles in the realm of commercial multipoint measurements.
Another object of the invention is to provide for an increased measurement accuracy.
In accordance with a particular embodiment of the invention, a multipoint measuring device comprises: a measuring bridge network; a plurality of transducers for converting a quantity under measurement to an electrical signal, said plurality of transducers divided into two identi-cal groups to be selectively connected in one arm of said measuring bridge network, a selector switch for selectively connecting one or the other of said two identical groups of transducers in said one arm of said measuring bridge network, a first, a second, a third and a fourth compensator for pro-viding a voltage to compensate for the impedance of the leads between said selector switch and said transducers and for the contact resistance of said selector switch; said first and third compensators belonging to said first transd~ar group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compensator being connected to a measurement point of a measuring diagonal of said bridge network; said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth compen-sator being connected to a measurement point of a measuring diagonal of said bridge network; said first transducer group -~ , ~` ~
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and said second transducer group connected alternatively in said one arm of said measuring bridge network by action of said selector switch via their said respective first, third, second and fourth compensators, whereby said first, third and second, fourth compensators provide voltage compensation for the impedance of the leads between said selector switch and said respective group of transducers and compensation for the contact resistance of said selector switch during a measure-ment operation.
In accordance with a further embodiment of the invention, a multipoint measuring device comprises: a measur-ing bridge network, a plurality of transducers for converting a ~uantity under measurement to an electrical signal, said plurality of transducers being divided into two identical groups; each transducer group connected in one of adjacent arms of said measuring bridge network: a selector switch used to connect said transducers in said adjacent arms of said measuring bridge network, a first, a second, a third and a fourth compensator providing voltage compensation for the impedance of the leads between said selector switch and said transducers and for the contact resistance of said selector switch; said first and third compensators belonging to said first transducer group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compen-sator being connected to a measurement point of a measuring diagonal of said bridge network; said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth compensator being connected to a measurement point of a measuring diagonal of said bridge network; said first transducer group connected in one arm .
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of said measuring bridge network via said first and third compensators and said second transducer group connected in the arm of said measuring bridge network adjacent to said one arm, via said second and fourth compensators, said con-nections being implemented by said selector switch so thatthe connection point of said third and fourth compensators is used as the measurement point of the measuring diagonal of said measuring bridge network, whereby said compensators act to provide a voltage to compensate for the impedance of the leads between said selector switch and transducers and compensation for the contact resistance of said switch.
Advantageously, the multipoint measuring device com-prises the transducers connected in one arm of the mea~uring bridge network along with a contact group of a measurement mode selector, connected in the same arm of the measuring - 4a -il~t7~332 bridge network, and with another contact group of the measu-rement mode selector, connected in the above-mentioned arm so that each contact group is coupled via its own compensator, or comprises the transducers connected in two adjacent arms of the measuri~g bridge network so that one of the main com-pensators is coupled to a supply point of a supply diagonal of the measuring bridge network via the contacts of said another contact group of the measurement mode selector and via the compensator of said another contact group.
Preferably, each arm of the measuring bridge network void of the transducers incorporates the contact groups of a measu-rement range selector and each said contact group is connect-ed in a respective arm of the measuring bridge network Yia a respective compensator of said contact group.
Advantageously, a part of the contacts of the measure-ment range selector is connected in the arms of the measuring bridge network via resistors.
Reliable operation of the proposed device is attained in a condition when one or more transducers is at fault. ~he de-vice provides for highly accurate measurements not influenced by harmful factors such as temperature, humidity and others.
Description of the Drawings Other features a~d advantages o~ the in~en-tion ~ill ap- ~-pear from the following description o~ a preferred embodiment thereof in conjunction with the accompanying drawin~s, in which:
Figure 1 is a schematic diagram of a multipoint measuri~g device provided with transducers connected in a single arm of a measuring bridge network, according to the invention;
Figure 2 is a schematic diagram of a multipoint measuring devic~ provided with transducers con~ected in two adjacent arms of the measuring bridge network, according to the inven-tion;
Figure 3 is a schematic diagram of a multipoint measuring device with a measurement mode selector and transducers con-nected in a single arm o~ -the measuring bridge network, ac-cording to the inventioni Figure 4 is a schematic diagram of a multipoint measuring device with the measurement mode selector and tra~sducers connected in two adjacent arms of the measuring bridge net-work, according to the invention;
Figure 5 is a schematic diagram of a multipoint measuring device with a measurement range selector and transducers con-nected in a single arm o~ the measuring bridge network, ac-cording to the invention;
Figure 6 is a schematic diagram of a multipoint measuringdevice with the measurement range selector and transducers connected in two adjacent arms of the measuring bridge nat-work, according to thè invention;
Figure 7 is a schematic diagram o~ a compensator, accord-ing to the invention;
Figure 8 is a detailed schematic diagram o~ a multipoint measuring device, according to the invention.
-' The multipoint measuring device of the invention, based on a measuring bridge network, comprises a supply diagonal ab (Fig. 1) which receives a supply voltage from a pulsed voltage source 1.
Transducers 2, 3 converting the quantity under measurement into an electrical signal (such as strain gauges, resistance thermometers and so on) are broken down into two identical groups. For the sake of convenience, each trans-ducer group is presented in Figure 1 as a single transducer.
Note, however, that each group may involve any number of transducers desirable.
The embodiment of Fig. 1 describes the transducers
Known in the art is a measuring device using a measuring bridge network the supply diagonal of which accepts a sine-wave or a d,c. supply voltage, Suply voltages taken from a power supply are delivered over a lead via two voltage regulators to a half-bridge network comprised of two series~
connected transducers (cf. Auslegeschrift No. 2,314,754, FRG), Such a circuit can utilize a single transducer if the adjacent arm of the circuit is provided with a compensating transducer or an auxiliary resistor. The known multipoint measuring device is inoperative if a single transducer is incorporated therein so that no compensating transducer or auxiliary resistor is used. The measurement points of a measuring diagonal of the known device, which are provided when the two transducers connect each other or a single transducer connects the compensating transducer of the auxiliary resistor, are combined using a common bus. This feature makes the known device inoperative if either of the transducers is accidentally connected to the ground bus.
Moreover, the known device can use transducers of identical characteristics with the result that a limited number of uses is possible in the case of multipoint measurements.
Although the known device provides for the transfer of the potential produced by the power supply without distortion, it is unable to resist the effect of the impedance of the leads between the common buses of the measurement points and the device subassemblies, as well as the effect of the ~;J
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contact resistances and their changes in the circuit resulting from the action of temperature, humidity and other disturb-ing factors. It is especially important to eliminate these harmful effects when small quantities are to be measured.
An object of the invention is to provide a multi-point measuring device which can be operated without troubles in the realm of commercial multipoint measurements.
Another object of the invention is to provide for an increased measurement accuracy.
In accordance with a particular embodiment of the invention, a multipoint measuring device comprises: a measuring bridge network; a plurality of transducers for converting a quantity under measurement to an electrical signal, said plurality of transducers divided into two identi-cal groups to be selectively connected in one arm of said measuring bridge network, a selector switch for selectively connecting one or the other of said two identical groups of transducers in said one arm of said measuring bridge network, a first, a second, a third and a fourth compensator for pro-viding a voltage to compensate for the impedance of the leads between said selector switch and said transducers and for the contact resistance of said selector switch; said first and third compensators belonging to said first transd~ar group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compensator being connected to a measurement point of a measuring diagonal of said bridge network; said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth compen-sator being connected to a measurement point of a measuring diagonal of said bridge network; said first transducer group -~ , ~` ~
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and said second transducer group connected alternatively in said one arm of said measuring bridge network by action of said selector switch via their said respective first, third, second and fourth compensators, whereby said first, third and second, fourth compensators provide voltage compensation for the impedance of the leads between said selector switch and said respective group of transducers and compensation for the contact resistance of said selector switch during a measure-ment operation.
In accordance with a further embodiment of the invention, a multipoint measuring device comprises: a measur-ing bridge network, a plurality of transducers for converting a ~uantity under measurement to an electrical signal, said plurality of transducers being divided into two identical groups; each transducer group connected in one of adjacent arms of said measuring bridge network: a selector switch used to connect said transducers in said adjacent arms of said measuring bridge network, a first, a second, a third and a fourth compensator providing voltage compensation for the impedance of the leads between said selector switch and said transducers and for the contact resistance of said selector switch; said first and third compensators belonging to said first transducer group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compen-sator being connected to a measurement point of a measuring diagonal of said bridge network; said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth compensator being connected to a measurement point of a measuring diagonal of said bridge network; said first transducer group connected in one arm .
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of said measuring bridge network via said first and third compensators and said second transducer group connected in the arm of said measuring bridge network adjacent to said one arm, via said second and fourth compensators, said con-nections being implemented by said selector switch so thatthe connection point of said third and fourth compensators is used as the measurement point of the measuring diagonal of said measuring bridge network, whereby said compensators act to provide a voltage to compensate for the impedance of the leads between said selector switch and transducers and compensation for the contact resistance of said switch.
Advantageously, the multipoint measuring device com-prises the transducers connected in one arm of the mea~uring bridge network along with a contact group of a measurement mode selector, connected in the same arm of the measuring - 4a -il~t7~332 bridge network, and with another contact group of the measu-rement mode selector, connected in the above-mentioned arm so that each contact group is coupled via its own compensator, or comprises the transducers connected in two adjacent arms of the measuri~g bridge network so that one of the main com-pensators is coupled to a supply point of a supply diagonal of the measuring bridge network via the contacts of said another contact group of the measurement mode selector and via the compensator of said another contact group.
Preferably, each arm of the measuring bridge network void of the transducers incorporates the contact groups of a measu-rement range selector and each said contact group is connect-ed in a respective arm of the measuring bridge network Yia a respective compensator of said contact group.
Advantageously, a part of the contacts of the measure-ment range selector is connected in the arms of the measuring bridge network via resistors.
Reliable operation of the proposed device is attained in a condition when one or more transducers is at fault. ~he de-vice provides for highly accurate measurements not influenced by harmful factors such as temperature, humidity and others.
Description of the Drawings Other features a~d advantages o~ the in~en-tion ~ill ap- ~-pear from the following description o~ a preferred embodiment thereof in conjunction with the accompanying drawin~s, in which:
Figure 1 is a schematic diagram of a multipoint measuri~g device provided with transducers connected in a single arm of a measuring bridge network, according to the invention;
Figure 2 is a schematic diagram of a multipoint measuring devic~ provided with transducers con~ected in two adjacent arms of the measuring bridge network, according to the inven-tion;
Figure 3 is a schematic diagram of a multipoint measuring device with a measurement mode selector and transducers con-nected in a single arm o~ -the measuring bridge network, ac-cording to the inventioni Figure 4 is a schematic diagram of a multipoint measuring device with the measurement mode selector and tra~sducers connected in two adjacent arms of the measuring bridge net-work, according to the invention;
Figure 5 is a schematic diagram of a multipoint measuring device with a measurement range selector and transducers con-nected in a single arm o~ the measuring bridge network, ac-cording to the invention;
Figure 6 is a schematic diagram of a multipoint measuringdevice with the measurement range selector and transducers connected in two adjacent arms of the measuring bridge nat-work, according to thè invention;
Figure 7 is a schematic diagram o~ a compensator, accord-ing to the invention;
Figure 8 is a detailed schematic diagram o~ a multipoint measuring device, according to the invention.
-' The multipoint measuring device of the invention, based on a measuring bridge network, comprises a supply diagonal ab (Fig. 1) which receives a supply voltage from a pulsed voltage source 1.
Transducers 2, 3 converting the quantity under measurement into an electrical signal (such as strain gauges, resistance thermometers and so on) are broken down into two identical groups. For the sake of convenience, each trans-ducer group is presented in Figure 1 as a single transducer.
Note, however, that each group may involve any number of transducers desirable.
The embodiment of Fig. 1 describes the transducers
2, 3 arranged in two groups which are connected in one arm of the measuring bridge network having its three other arms provided with resistors 4, 5, 6. The transducers 2, 3 are connected in the bridge network via a selector switch 7, identical compensators 8, 9 and compensators 10, 11 identical to compensators 8, 9 which operate to compensate for the impedance of the leads and for the contact resistance of the selector switch 7. me number of selector stages of the selector switch 7 is chosen depending on conditions of reliable operation and may be as great as desirable (a two-stage selector switch 7 is used in the embodiment of Fig. 1). .
The two groups of the transducers 2, 3 are placed alternately in one arm of the measuring bridge network through the selector switch 7 and the identical compensators .i 8 - 11, said first transducer group 2 being connected through the compensators 8, 10 and said second transducer group 3 being connected through the compensators 9, 11.
Moreover, the compensator 10 or 11 is always con-nected to a measurement point c of a measuring diagonal cd.
Figure 2 illustrates an embodiment of the multi-point measuring device of the invention, wherein the trans-ducer groups 2, 3 are connected in two adjacent arms of the measuring bridge network, the connection point of the compensators 10, 11 being coupled to the measurement point c of the measuring diagonal cd.
Figure 3 illustrates an embodiment of the multi-point measuring device of the invention, providing a measure-ment mode selector 12 operated to switch over from a half-bridge circuit to a single transducer. One contact group 13of the measurement mode selector 12 is placed via a compensator 1~ -n that arm of the me~Cllring bridge network which incor-porates the transducers 2, 3, while another contact group 15 of the measurement mode selector 12 is placed via a compen-sator 16 in the same arm. A compensator 14 identical tocompensators 8 - 11 is connected to the measurement point c of the measuring diagonal cd.
Figure 4 illustrates an embodiment of the multi-point measuring device of the invention having its trans-ducers Z, 3 connected in two adjacent arms of the measuringbridge network with the help of the measurement mode selector 12 whose contact group 17 is placed in one of the adjacent ,~
~7~2 arms via the compensator 16 identical to compensators 8 - 11.
The compensators 10, 11 are connected to the measurement point c of themeasuring diagonal cd.
Figures 5, 6 illustrate an embodiment of the multi-point measuring device provided with a measurement rangeselector 18.
Contact groups 19, Z0, 21 of the measurement range selector 18 are placed in respective arms of the measuring bridge network via their respective compensators 22, 14, 23 and via their respective auxiliary resistors 24, 25, 26. The embodiments of Figs. 5, 6 differ from one another in that the transducers 2, 3 are connected in one arm of the measurement bridge network (Fig. 5) and in two adjacent arms thereof (Fig. 6).
A compensator shown in Figure 7 can be used as any one of the above-mentioned compensators 8 - 11, 14, 16, 22, 23, This compensator comprises an operational amplifier 27 and two separate power sources 28, 29 having their mid point connected to the non-inverted input of the operational ampli-fier 27 and used as an input 30 of the compensator.
The inverted input of the operational amplifier 27 is coupled to its output via contacts which may be generally as follows: the contacts between the leads of the selector switch 7 and the transducers, the contacts of the contact groups of the measurement mode selector 12, and/or the con-tacts of the contact groups of the measurement range selector 18. Figure 7 shows the use of the contacts of contact groups 31, 21 of the measurement range selector 18, note that the ~'7~3~2 contacts 31 are closed and the contacts 21 are open. Common points 32, 33, 34 of contact groups 31 - 21 are coupled either in a direct way (the point 32 is coupled to a second input 35 of the compensator) or through resistors 26 whose number is equal to that: o~ the ratings of the transducers used in the multipoint measuring device. This also applies to the selection of the resistors 24, 25, 26 (Figs. 5, 6) placed in the other arr,ls of the measuring bridge network, an equal num~er of thec;e resistors being selected for each set of the transducers.
Figure 8 illustrates a detailed schematic diagram of the multipoint measuring device provided with two groups of the transducers 2, :3 (hereinafter referred to as trans-ducers groups 2, 3) incorporated in two adjacent arms of the measuring bridge network. The proposed device has the measure-ment mode selector 12 with contact groups 13, 15, 17 and the measurement range selector 18 with contact groups 36, 19, 37, 20, 31, 21. Each said contact group is placed in a respective arm of the measuring bridge network via its respective compensator. The contact groups 13, 15, 17 of the measurement mode selector 12 are provided with their respective compensators 14, 16, while the contact groups 36, ~ 19 and 31, 21 of the measurement range selector 18 are pro-,~` vided with their respective compensators 22, 23. The contact groups 37, 20 of the measurement range selector 18 are con-nected through the compensator 14 together with the contact group 13 of the measurement mode selector 12.
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~ he contact groups 19 - 21 of ths measurement range se-lector 18 are placed in their respective arms of the measur-ing bridge network via respective resistors 24 - 26.
~ he selector switch 7 is controlled with the help of a control unit 38.
A null indicator 39 is inserted in the measuring diagonal cd of the measuring bridge network. The power source 1 is a heteropolar pulse generator coupled to a bit-by-bit balancer 40 which opèrates to control a conductance box 41.
An input 42 and outputs 43, 44 of the bit-by-bit balancer 40 are coupled to a computer (not shown in the drawings) which provides ~or synchronized operation of the control unit 38, the bit-by-bit balancer 40 and the heteropolar pulse generator.
The computer receives measurement results and processes them.
; The multipoint measuring device o~ tne invenbion operates as follows.
With the transducers placed in a certain arm of the mea-suring bridge network, the required transducer is selected by making respective contacts of the matrices of ths selector switch 7. This is attained in any conventional manner accord-ing to a signal available from the control unit 38. The trans-ducer group 2 is ~irst connected between the measurement point c and the supply point a. In this mode, the contact group 13 of the measurement mode selector 12 is closed and the contact resistance o~ this group is eliminated by the compe~sator 14.
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I~ the rating o~ the transducer incorporated in an arm of the measuring bridge network corresponds to the ratings o~
the resistors 4, 5, 6 in the remaining arms, then the contact groups 36, 37, 31 of the measurement range selector 18 are clos~d to prevent the resistors 24 - 26 from being placed in respective arms o~ the measuring bridge network. If the rating o~ the transducer exceeds the ratings o~ the resistors 4 - 6 in the remaining arms, then the contact groups 36, 37, 31 are open and the resistors 24 - 26 are connected in respective arms o~ the measuring bridge network via the closed contact groups 19, 20, 21.
A~ter the transducer group 2 has been interrogated, the transducer group 3 is enabled and the contact groups 13, 15 of the measurement mode selector 12 are closed in this case.
The position o~ the measurement range selector 18 is determin-ed as described above.
~ ow consider an operating mode in which two transducers, each of which belongs to its respective transducer group 2 and 3, are connected concurrently in two adjacent arms o~ the measuring bridge network as ~oliows: the transducer o~ the transducer group 2 is placed between the measureme~t point c and the supply point a, and the transducer o~ the transducer group 3 is placed between the measurement point c and the supply point b. An order according to which the transducers are connected within their respective transducer groups 2, 3 is determined by a respective signal from the control unit 38 by switching over the contacts o~ the selector s~vitch 7.
In this mode, the contact group 17 of the measure-ment mode selector 12 is closed and the contact groups 13, 15 of this selector are made open.
In any measurement mode, a signal from the measur-ing diagonal cd comes to the input of the null indicator 39 and the bit-by-bit balancer 40 is activated each time the phase of the signal is changed. Balance of the measuring bridge network is made during each step of the measurement cycle by shunting the arm of the network, containing the resistor 5, with the help of the conductance box 41 which has the ratings of its legs proportional to binary code.
At balance the output of the bit-by-bit balancer 40 produces ~
a numerical equivalent of the increment value of the resist-ance of the transducer in a respective arm of the measuring L5 bridge network. The computer operates to synchronize the operation of the control unit, 38, the bit-by-bit balancer 40 and the heteropolar pulse generator and to process measurement results delivered to it from the bit-by-bit balancer 40.
The compensators 8 - 11, 14, 16, 22, 23 operate ; to prevent the measurement results from being affected by the impedance of the leads between the selector switch 7 and the transducers as well as random changes occurred in the impedance. Also, the effect of the contact resist-ance of the selector switch 7, the measurement mode selector 12 and the measurement range selector 18 is eliminated with the result that measurement accuracy not worse than 0.1% is attained ~ ~,.
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due to the fact that key equivalents are formed which have a negligible resistance.
rl'he transducer groups 2, 3 connected in the measuring bridge network with the help of the selector switch 7 make it pos~iblo to allmi~ab~ the influenc~ o~ a ~aulty transduc-er circuit on measurement results provided by the remaining transducers. ~he proposed device can connect a single trans-ducer in a single arm or several transducers in a half-bridge circuit. ~ihe measurement range selector 18 pro~ides for the use of transducers of different ratings, thereby resulting in greater number of possible applications of the device.
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The two groups of the transducers 2, 3 are placed alternately in one arm of the measuring bridge network through the selector switch 7 and the identical compensators .i 8 - 11, said first transducer group 2 being connected through the compensators 8, 10 and said second transducer group 3 being connected through the compensators 9, 11.
Moreover, the compensator 10 or 11 is always con-nected to a measurement point c of a measuring diagonal cd.
Figure 2 illustrates an embodiment of the multi-point measuring device of the invention, wherein the trans-ducer groups 2, 3 are connected in two adjacent arms of the measuring bridge network, the connection point of the compensators 10, 11 being coupled to the measurement point c of the measuring diagonal cd.
Figure 3 illustrates an embodiment of the multi-point measuring device of the invention, providing a measure-ment mode selector 12 operated to switch over from a half-bridge circuit to a single transducer. One contact group 13of the measurement mode selector 12 is placed via a compensator 1~ -n that arm of the me~Cllring bridge network which incor-porates the transducers 2, 3, while another contact group 15 of the measurement mode selector 12 is placed via a compen-sator 16 in the same arm. A compensator 14 identical tocompensators 8 - 11 is connected to the measurement point c of the measuring diagonal cd.
Figure 4 illustrates an embodiment of the multi-point measuring device of the invention having its trans-ducers Z, 3 connected in two adjacent arms of the measuringbridge network with the help of the measurement mode selector 12 whose contact group 17 is placed in one of the adjacent ,~
~7~2 arms via the compensator 16 identical to compensators 8 - 11.
The compensators 10, 11 are connected to the measurement point c of themeasuring diagonal cd.
Figures 5, 6 illustrate an embodiment of the multi-point measuring device provided with a measurement rangeselector 18.
Contact groups 19, Z0, 21 of the measurement range selector 18 are placed in respective arms of the measuring bridge network via their respective compensators 22, 14, 23 and via their respective auxiliary resistors 24, 25, 26. The embodiments of Figs. 5, 6 differ from one another in that the transducers 2, 3 are connected in one arm of the measurement bridge network (Fig. 5) and in two adjacent arms thereof (Fig. 6).
A compensator shown in Figure 7 can be used as any one of the above-mentioned compensators 8 - 11, 14, 16, 22, 23, This compensator comprises an operational amplifier 27 and two separate power sources 28, 29 having their mid point connected to the non-inverted input of the operational ampli-fier 27 and used as an input 30 of the compensator.
The inverted input of the operational amplifier 27 is coupled to its output via contacts which may be generally as follows: the contacts between the leads of the selector switch 7 and the transducers, the contacts of the contact groups of the measurement mode selector 12, and/or the con-tacts of the contact groups of the measurement range selector 18. Figure 7 shows the use of the contacts of contact groups 31, 21 of the measurement range selector 18, note that the ~'7~3~2 contacts 31 are closed and the contacts 21 are open. Common points 32, 33, 34 of contact groups 31 - 21 are coupled either in a direct way (the point 32 is coupled to a second input 35 of the compensator) or through resistors 26 whose number is equal to that: o~ the ratings of the transducers used in the multipoint measuring device. This also applies to the selection of the resistors 24, 25, 26 (Figs. 5, 6) placed in the other arr,ls of the measuring bridge network, an equal num~er of thec;e resistors being selected for each set of the transducers.
Figure 8 illustrates a detailed schematic diagram of the multipoint measuring device provided with two groups of the transducers 2, :3 (hereinafter referred to as trans-ducers groups 2, 3) incorporated in two adjacent arms of the measuring bridge network. The proposed device has the measure-ment mode selector 12 with contact groups 13, 15, 17 and the measurement range selector 18 with contact groups 36, 19, 37, 20, 31, 21. Each said contact group is placed in a respective arm of the measuring bridge network via its respective compensator. The contact groups 13, 15, 17 of the measurement mode selector 12 are provided with their respective compensators 14, 16, while the contact groups 36, ~ 19 and 31, 21 of the measurement range selector 18 are pro-,~` vided with their respective compensators 22, 23. The contact groups 37, 20 of the measurement range selector 18 are con-nected through the compensator 14 together with the contact group 13 of the measurement mode selector 12.
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~ he contact groups 19 - 21 of ths measurement range se-lector 18 are placed in their respective arms of the measur-ing bridge network via respective resistors 24 - 26.
~ he selector switch 7 is controlled with the help of a control unit 38.
A null indicator 39 is inserted in the measuring diagonal cd of the measuring bridge network. The power source 1 is a heteropolar pulse generator coupled to a bit-by-bit balancer 40 which opèrates to control a conductance box 41.
An input 42 and outputs 43, 44 of the bit-by-bit balancer 40 are coupled to a computer (not shown in the drawings) which provides ~or synchronized operation of the control unit 38, the bit-by-bit balancer 40 and the heteropolar pulse generator.
The computer receives measurement results and processes them.
; The multipoint measuring device o~ tne invenbion operates as follows.
With the transducers placed in a certain arm of the mea-suring bridge network, the required transducer is selected by making respective contacts of the matrices of ths selector switch 7. This is attained in any conventional manner accord-ing to a signal available from the control unit 38. The trans-ducer group 2 is ~irst connected between the measurement point c and the supply point a. In this mode, the contact group 13 of the measurement mode selector 12 is closed and the contact resistance o~ this group is eliminated by the compe~sator 14.
1 1~ 7 ~ 3 Z
I~ the rating o~ the transducer incorporated in an arm of the measuring bridge network corresponds to the ratings o~
the resistors 4, 5, 6 in the remaining arms, then the contact groups 36, 37, 31 of the measurement range selector 18 are clos~d to prevent the resistors 24 - 26 from being placed in respective arms o~ the measuring bridge network. If the rating o~ the transducer exceeds the ratings o~ the resistors 4 - 6 in the remaining arms, then the contact groups 36, 37, 31 are open and the resistors 24 - 26 are connected in respective arms o~ the measuring bridge network via the closed contact groups 19, 20, 21.
A~ter the transducer group 2 has been interrogated, the transducer group 3 is enabled and the contact groups 13, 15 of the measurement mode selector 12 are closed in this case.
The position o~ the measurement range selector 18 is determin-ed as described above.
~ ow consider an operating mode in which two transducers, each of which belongs to its respective transducer group 2 and 3, are connected concurrently in two adjacent arms o~ the measuring bridge network as ~oliows: the transducer o~ the transducer group 2 is placed between the measureme~t point c and the supply point a, and the transducer o~ the transducer group 3 is placed between the measurement point c and the supply point b. An order according to which the transducers are connected within their respective transducer groups 2, 3 is determined by a respective signal from the control unit 38 by switching over the contacts o~ the selector s~vitch 7.
In this mode, the contact group 17 of the measure-ment mode selector 12 is closed and the contact groups 13, 15 of this selector are made open.
In any measurement mode, a signal from the measur-ing diagonal cd comes to the input of the null indicator 39 and the bit-by-bit balancer 40 is activated each time the phase of the signal is changed. Balance of the measuring bridge network is made during each step of the measurement cycle by shunting the arm of the network, containing the resistor 5, with the help of the conductance box 41 which has the ratings of its legs proportional to binary code.
At balance the output of the bit-by-bit balancer 40 produces ~
a numerical equivalent of the increment value of the resist-ance of the transducer in a respective arm of the measuring L5 bridge network. The computer operates to synchronize the operation of the control unit, 38, the bit-by-bit balancer 40 and the heteropolar pulse generator and to process measurement results delivered to it from the bit-by-bit balancer 40.
The compensators 8 - 11, 14, 16, 22, 23 operate ; to prevent the measurement results from being affected by the impedance of the leads between the selector switch 7 and the transducers as well as random changes occurred in the impedance. Also, the effect of the contact resist-ance of the selector switch 7, the measurement mode selector 12 and the measurement range selector 18 is eliminated with the result that measurement accuracy not worse than 0.1% is attained ~ ~,.
'' ,~
.. :
~78~
due to the fact that key equivalents are formed which have a negligible resistance.
rl'he transducer groups 2, 3 connected in the measuring bridge network with the help of the selector switch 7 make it pos~iblo to allmi~ab~ the influenc~ o~ a ~aulty transduc-er circuit on measurement results provided by the remaining transducers. ~he proposed device can connect a single trans-ducer in a single arm or several transducers in a half-bridge circuit. ~ihe measurement range selector 18 pro~ides for the use of transducers of different ratings, thereby resulting in greater number of possible applications of the device.
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Claims (8)
1. A multipoint measuring device comprising a measuring bridge network;
a plurality of transducers for converting a quantity under measurement to an electrical signal, said plurality of transducers divided into two identical groups to be select-ively connected in one arm of said measuring bridge network:
a selector switch for selectively connecting one or the other of said two identical groups of transducers in said one arm of said measuring bridge network;
a first, a second, a third and a fourth compen-sator for providing a voltage to compensate for the impedance of the leads between said selector switch and said trans-ducers and for the contact resistance of said selector switch;
said first and third compensators belonging to said first transducer group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compen-sator being connected to a measurement point of a measuring diagonal of said bridge network;
said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth com-pensator being connected to a measurement point of a measur-ing diagonal of said bridge network;
said first transducer group and said second trans-ducer group connected alternatively in said one arm of said measuring bridge network by action of said selector switch via their said respective first, third, second and fourth compensators, whereby said first, third and second, fourth compensators provide voltage compensation for the impedance of the leads between said selector switch and said respective group of transducers and compensation for the contact resist-ance of said selector switch during a measurement operation.
a plurality of transducers for converting a quantity under measurement to an electrical signal, said plurality of transducers divided into two identical groups to be select-ively connected in one arm of said measuring bridge network:
a selector switch for selectively connecting one or the other of said two identical groups of transducers in said one arm of said measuring bridge network;
a first, a second, a third and a fourth compen-sator for providing a voltage to compensate for the impedance of the leads between said selector switch and said trans-ducers and for the contact resistance of said selector switch;
said first and third compensators belonging to said first transducer group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compen-sator being connected to a measurement point of a measuring diagonal of said bridge network;
said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth com-pensator being connected to a measurement point of a measur-ing diagonal of said bridge network;
said first transducer group and said second trans-ducer group connected alternatively in said one arm of said measuring bridge network by action of said selector switch via their said respective first, third, second and fourth compensators, whereby said first, third and second, fourth compensators provide voltage compensation for the impedance of the leads between said selector switch and said respective group of transducers and compensation for the contact resist-ance of said selector switch during a measurement operation.
2. A multipoint measuring device comprising:
a measuring bridge network;
a plurality of transducers for converting a quantity under measurement to an electrical signal, said plurality of transducers being divided into two identical groups;
each transducer group connected in one of the adjacent arms of said measuring bridge network;
a selector switch used to connect said transducers in said adjacent arms of said measuring bridge network;
a first, a second, a third and a fourth compensator providing voltage compensation for the impedance of the leads between said selector switch and said transducers and for the contact resistance of said selector switch;
said first and third compensators belonging to said first transducer group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compensator being connected to a measurement point of a measuring diagonal of said bridge network;
said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth com-pensator being connected to a measurement point of a measur-ing diagonal of said bridge network;
said first transducer group connected in one arm of said measuring bridge network via said first and third compensators and said second transducer group connected in the arm of said measuring bridge network adjacent to said one arm, via said second and fourth compensators, said con-nections being implemented by said selector switch so that the connection point of said third and fourth compensators is used as the measurement point of the measuring diagonal of said measuring bridge network, whereby said compensators act to provide a voltage to compensate for the impedance of the leads between said selector switch and transducers and compensation for the contact resistance of said switch.
a measuring bridge network;
a plurality of transducers for converting a quantity under measurement to an electrical signal, said plurality of transducers being divided into two identical groups;
each transducer group connected in one of the adjacent arms of said measuring bridge network;
a selector switch used to connect said transducers in said adjacent arms of said measuring bridge network;
a first, a second, a third and a fourth compensator providing voltage compensation for the impedance of the leads between said selector switch and said transducers and for the contact resistance of said selector switch;
said first and third compensators belonging to said first transducer group, each being connected to said selector switch, said first compensator being connected to a supply point of said bridge network and said third compensator being connected to a measurement point of a measuring diagonal of said bridge network;
said second and fourth compensators belonging to said second transducer group, each being connected to said selector switch, said second compensator being connected to a supply point of said bridge network and said fourth com-pensator being connected to a measurement point of a measur-ing diagonal of said bridge network;
said first transducer group connected in one arm of said measuring bridge network via said first and third compensators and said second transducer group connected in the arm of said measuring bridge network adjacent to said one arm, via said second and fourth compensators, said con-nections being implemented by said selector switch so that the connection point of said third and fourth compensators is used as the measurement point of the measuring diagonal of said measuring bridge network, whereby said compensators act to provide a voltage to compensate for the impedance of the leads between said selector switch and transducers and compensation for the contact resistance of said switch.
3. A multipoint measuring device as claimed in claim 1, comprising:
a fifth and a sixth compensator;
a measurement mode selector with contacts arranged in two groups;
said first contact group of said measurement mode selector, connected via said fifth compensator in the arm of said measuring bridge network, which incorporates said transducers;
said second contact group of said measurement mode selector, connected via said sixth compensator in the same arm of said measuring bridge network.
a fifth and a sixth compensator;
a measurement mode selector with contacts arranged in two groups;
said first contact group of said measurement mode selector, connected via said fifth compensator in the arm of said measuring bridge network, which incorporates said transducers;
said second contact group of said measurement mode selector, connected via said sixth compensator in the same arm of said measuring bridge network.
4. A multipoint measuring device as claimed in claim 2, comprising:
a fifth compensator;
said measurement mode selector with contacts, con-nected via said fifth compensator in one arm of said measur-ing bridge network, which incorporates one of said transducer groups, said fifth compensator being coupled to a supply point of a supply diagonal of said measuring bridge network.
a fifth compensator;
said measurement mode selector with contacts, con-nected via said fifth compensator in one arm of said measur-ing bridge network, which incorporates one of said transducer groups, said fifth compensator being coupled to a supply point of a supply diagonal of said measuring bridge network.
5. A multipoint measuring device as claimed in claim 3, comprising:
a measurement range selector with contact groups;
said contact groups connected in the remaining arms of said measuring bridge network;
a seventh, an eighth and a ninth compensator used to place each respective contact group of said contact groups of said measurement range selector in a respective arm of said measuring bridge network.
a measurement range selector with contact groups;
said contact groups connected in the remaining arms of said measuring bridge network;
a seventh, an eighth and a ninth compensator used to place each respective contact group of said contact groups of said measurement range selector in a respective arm of said measuring bridge network.
6. A multipoint measuring device as claimed in claim 4, comprising:
said measurement range selector with contact groups;
said contact groups connected in the remaining arms of said measuring bridge network;
a sixth and a seventh compensator used to place each respective contact group of said contact groups of said measure-ment range selector in a respective arm of said measuring bridge network.
said measurement range selector with contact groups;
said contact groups connected in the remaining arms of said measuring bridge network;
a sixth and a seventh compensator used to place each respective contact group of said contact groups of said measure-ment range selector in a respective arm of said measuring bridge network.
7. A multipoint measuring device as claimed in claim 5, comprising resistors connected in those arms of said measuring bridge network which incorporate said contact groups of said measurement range selector.
8. A multipoint measuring device as claimed in claim 6, comprising resistors connected in those arms of said measuring bridge network which incorporate said contact groups of said measurement range selector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA301,644A CA1107832A (en) | 1978-04-21 | 1978-04-21 | Multipoint measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA301,644A CA1107832A (en) | 1978-04-21 | 1978-04-21 | Multipoint measuring device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1107832A true CA1107832A (en) | 1981-08-25 |
Family
ID=4111301
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA301,644A Expired CA1107832A (en) | 1978-04-21 | 1978-04-21 | Multipoint measuring device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1107832A (en) |
-
1978
- 1978-04-21 CA CA301,644A patent/CA1107832A/en not_active Expired
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