GB2031165A - Creation of Inventions and Patents with Artificial Intelligence

GB2031165A – Determining absolute value and polarity of electrical parameters
– Google Patents

GB2031165A – Determining absolute value and polarity of electrical parameters
– Google Patents
Determining absolute value and polarity of electrical parameters

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Publication number
GB2031165A

GB2031165A
GB7925895A
GB7925895A
GB2031165A
GB 2031165 A
GB2031165 A
GB 2031165A
GB 7925895 A
GB7925895 A
GB 7925895A
GB 7925895 A
GB7925895 A
GB 7925895A
GB 2031165 A
GB2031165 A
GB 2031165A
Authority
GB
United Kingdom
Prior art keywords
amplifier
indicator according
current
disposed
voltage
Prior art date
1978-07-27
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Granted

Application number
GB7925895A
Other versions

GB2031165B
(en

Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

CGS APPARECCH

Original Assignee
CGS APPARECCH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1978-07-27
Filing date
1979-07-25
Publication date
1980-04-16

1979-07-25
Application filed by CGS APPARECCH
filed
Critical
CGS APPARECCH

1980-04-16
Publication of GB2031165A
publication
Critical
patent/GB2031165A/en

1982-11-10
Application granted
granted
Critical

1982-11-10
Publication of GB2031165B
publication
Critical
patent/GB2031165B/en

Status
Expired
legal-status
Critical
Current

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Classifications

G—PHYSICS

G01—MEASURING; TESTING

G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES

G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 – G01R29/00, G01R33/00 – G01R33/26 or G01R35/00

G01R15/12—Circuits for multi-testers, i.e. multimeters, e.g. for measuring voltage, current, or impedance at will

G—PHYSICS

G01—MEASURING; TESTING

G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES

G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof

G01R19/14—Indicating direction of current; Indicating polarity of voltage

Abstract

The absolute value of an electrical parameter is derived by rectification 15 of a proportional current Im and is displayed on a meter 17, while the polarity of the parameter is derived and separately displayed 26 on the meter panel by injecting into the signal path a polarity-representing signal Ia, the presence of which is subsequently detected. An oscillator 19 of relatively high frequency injects a signal Va into the input 4 of an operational amplifier 10 whenever an FET 18 is turned on by a signal Vi of appropriate polarity. The output current Ia arising from the injected signal actuates LEDs 26 but is blocked 28 from the rectifying bridge 15, whereas the current Im to be measured is blocked from the LEDs 26 by a capacitor 27. The presence of a Zener diode 16 downstream of the bridge 15 produces a step in the voltage output of the amplifier 10 at the zero crossings to assist the switching of FET 18.

Description

SPECIFICATION
A panel instrument for indicating electric parameters and having light sign Indicators
The invention relates to panel indicating instruments for measuring electric parameters having positive or negative values.
More particularly, the invention relates to indicating instruments comprising a converter comprising a current generator type outlet amplifier whose output terminals are adapted to generate a current directly proportional to the voltage signals applied to its input terminals, the converter generating the measuring voltage indicating the value and sign of the measured parameter and supplying the measuring voltage to a first input of the outlet amplifier; the output terminals of the outlet amplifier supplying a measuring current, depending on the measuring voltage supplied to its first input, for supplying a miliiammeter indicating instrument via a pair of leads.
In the aforementioned indicating instruments, the problem of showing the sign of the measured parameter is solved, in the prior art, by providing the instruments with a reading scale having a central zero, i.e. containing a first half-sector for indicating values having one sign and a second half-sector for indicating values having the opposite sign.
This method, however, has serious disadvantages, particularly when the reading scale is of the 90″ kind.
Firstly, since the two half-sectors of the scale are symmetrical, one indicating positive values and the other indicating negative values, the effective width of the scale is reduced by half, so that the accuracy of reading is clearly less than that obtainable by using the entire width of the scale.
Secondly, when the instrument is inoperative, its pointer must be permanently positioned halfway along the scale – in the case of a 90″ scale, the pointer when inoperative is at a position inclined at 45″. This requires special calibration of the instrument, i.e. it takes longer to prepare.
Furthermore, since most indicating instruments are adapted to measure an absolute value, and consequently most reading scales have a zero at the side, a central-zero scale has to be produced in accordance with a special design, which is different from that required for most commerical indicating instruments and is therefore more expensive.
The object of the invention is to construct an indicating instrument of the aforementioned kind which obviates the aforementioned disadvantages, is particularly simple and econqmic and, more particularly, can be manufactured from widely available electric components without specially complex or expensive modifications.
To this end, the invention relates to an indicator of the aforementioned kind characterised in that the outlet amplifier generates the measuring current 1m in one or the other direction depending on the sign of the measured electrical parameter and the milliammeter instrument has a scale for reading absolute values only, the panel instrument also comprising: a rectifying bridge disposed between the outlet terminals of the outlet amplifier and the milliammeter instrument in order to rectify the measuring current;
transducer means disposed in series with the milliammeter instrument for generating a substantially constant voltage when the measuring current travels through them;
switch means actuated by a control voltage produced at the outlet terminals of the outlet amplifier from the voltage generated by the transducer means and adapted to change to the closed or the open state depending on the sign of the control voltage;
an oscillator adapted to produce a periodic voltage signal having a frequency much higher than the frequency of variation of the measured electrical parameter and adapted to be connected or disconnected by the switch means to or from a second input of the current amplifier;;
and sign-indicating means disposed in the reading panel of the ammeter instrument and actuated, via the aforementioned pairs of leads, by a supply current generated by the outlet amplifier when the oscillator is connected to the second input of the outlet amplifer.
The invention will now be described with reference to the accompanying drawings, given by way of non-limitative example, in which:
Figure 1 is a circuit diagram of an embodiment of an indicating instrument according to the invention, and
Figure 2 shows two diagrams indicating the variation in time of two electric parameters relating to the circuit in Figure 1.
Reference 1 denotes a current-generator type amplifier (also called “impressed-current” amplifier) comprising the final stage of a converter which in turn forms part of an indicating device for measuring electric parameters which can have either positive or negative values. Wattmeters, varmeters and cos phi meters are examples of indicating instruments of the aforementioned kind.
The converterstages (not shown in Figure 1) disposed upstream of the outlet amplifier 1 generate and supply a first input 2 of amplifier 1 with a voltage signal Vi indicating the value and sign of the measured electric parameter.
The outlet amplifier 1 comprises an operations amplifier 3whose “inverting” input 4 is connected to input 2 via a resistor 5 and to earth via a feedback resistor6 and a resistor 7 having a much lower value than resistor 6. The “non-inverting” input 8 of operations amplifier 3 is connected to earth via a bias resistor 9.
Output 10 of amplifier 3 supplies the two BASI, which are both connected by a stage 11 havjng complementary transistors whose collectors are connected to the positive +Vcc and negative supply respectively and whose emitters are connected together and also to a first output terminal 12 of amplifer 1.
A second output terminal 13 of amplifier 1 is connected to the common terminals of feedback resistor 6 and resistor 7.
In accordance with the theory of operations amplifiers, the current produced by output terminals 12, 13 of amplifier 1 is directly proportional to the voltage signals applied to the input of operations amplifier 3.
More particularly, the voltage signal Vi applied to input 2 causes the terminals 12, 13 of amplifier 1 to produce a measuring current Im having a value proportional to the signal Vi and flowing in a direction (e.g.
leaving or entering terminal 12) depending on whether Vi is positive or negative.
Consequently, the value of the measuring current Im indicates the measured parameter, whereas its direction of flow shows whether the parameter is positive or negative.
More specifically, the relation between the measuring current Im and the voltage signal Vi is given by the following formula:
provided that R2 > > R4, where R2, R1, R4 are the resistances of resistors, 6,5 and 7 respectively. The output terminals 12,13 of amplifier 1 (which is previously described, is of the impressed current kind) are connected by a pair of leads 14 to the supply diagonai of a rectifying bridge 15 whose output diagonal is connected by a Zener diode 16 to a milliammeter indicating instrument 17.
Instrument-17, which receives the rectified measuring current Im, has a scale with a side zero instead of a scale with a central zero, which would have been necessary if bridge 15 had not been used.
When the measuring current Im flows through Zener diode 16, the terminals thereof are at a Zener voltage which is substantially constant when Im.varies.
As a result of the Zener diode 16 and the fact that the measuring current Im is substantially independent of the load through which it travels, the voltage Vc between terminals 12, 13 of amplifier 1 is increased or reduced by the Zener voltage Vz of diode 16 according to whether 1m is positive or negative, i.e. is leaving or entering the output terminal 12.
Figure 2 by way of example, shows the variation in time of the measuring current 1m and the corresponding variation in time in the output voltage Vc.
The Zener voltage V2 is made equal to about half the supply voltage Vcc to avoid saturating amplifier 1. The changer +V3 or -V in the output voltage Vc also occurs, of course, at the output 10 of operations amplifier 3 and constitutes the control voltage for a field effect transistor (FET) 18 used as a switch.
FET 18 permits or prevents (when on or off respectively) the connecting of a signal generator 19 to a second input 20 of amplifier 1.
Input 20 is connected by a resistor 21 to the “inverting” input 4 of operations amplifier 3.
Generator 19 comprises an oscillator generating a signal having a frequency of about 5KHz.
A diode 22 is disposed between the gate terminal of FET 18 and the output 10 of amplifier 3, to protect the
FET.
A resistor 23, connected to the drain terminal of FET 18, constitutes the load of oscillator 19, which is connected to the source terminal of the FET.
A capacitor 24 is provided for decoupling, during direct current operation, the group comprising generator 19 and load 23 from the second input20 of amplifier 1.
A capacitor 25 is disposed in parallel with resistor 7; its reactance, at the frequecy of the signal generated by oscillator 19, is much less than the resistance of resistor 7.
If Va is the voltage of the second input 20 of amplifer 1 due to oscillator 19, it follows from the theory of operations amplifiers that voltage Va causes the output terminals 12, 13 of amplifier 1 to produce a supply current la-depending on voltage Va in accordance with the following formula:
where R2, Rs, C and w respectively denote the resistance of resistor 6, the resistance of resistor 21, the capacitance of conductor 25 and the angular frequency of the signal generated by oscillator 19.
The supply current la is supplied by leads 14 to a pair of light emission diodes (LED) 26 connected in anti-parallel. A capacitor 27 disposed in series with diodes 26 prevents the measuring current 1m from flowing in diodes LED 26 and a band-rejecting filter-28 placed in series with bridge 15 prevents the supply current Ia flowing in bridge 15 and consequently in the indicating instrument 17.
As the preceding description clearly shows, the sign of the measured electric parameter causes the measuring current 1m and the Zener diode 16 to generate a control voltage which, depending on the sign, is positive or negative.
The control voltage, depending on its sign, permits or prevents the supply current Is reaching diodes LED 26 via’conductors-14, through’which the measuring current 1m flows.
Diodes 26, which are dispdsed in the reading panel of milliammeter 17, are either on or off and thus indicate the sign of the measured parameter, so that milliammeter 17 only has to indicate the absolute value of the measuring current Iml i.e. the absolute value of the measured parameter. Consequently, milliammeter 17 does not need reading scale having a central zera, since an absolute-value reading scale having a side zero is quite sufficient.
A capacitor 25 is provided owing to the need to have a supply current la which is much higher than the measuring current 1m (Im < 5mA; 1a > 20 mA).
Filter LC 28 can be replaced by a capacitive filter connected in parallel with the rectifying bridge 15. LED diodes 26, each of which is acted upon by one half-wave of the signal generated by oscillator 19, may if required by replaced by a single incandescent lamp or by other kinds of indicating devices.
As already stated, diodes 26 are disposed on the panel of the miliiammeter instrument 17. Bridge 15,Zener diode 16, filter 28 and capacitor 27 are mounted in a small printed circuit and are contained in the container around milliammeter 17. Accordingly, the indicating instruments according to the invention can be milliammeters similar to those used in most commerical indicating instruments, the only slight modification being that a small printed whisker comprising the aforementioned very few electronic components is also placed inside the milliammeter container.
Since generator 19 is normally present in existing converters, the aforementioned indicating instrument can be constructed simply by inserting a limited number of components (i.e. FET 18, its diode 22, resistors 23 and 21 and capacitor 24) in existing converters. Accordingly the modifications required for obtaining an indicating instrument according to the invention are avaiiable commercially and are therefore very simple and, more particularly very economic.
Of course, without altering the principle of the invention, the embodiments thereof can be widely varied from what has been described and illustrated, without thereby departing from the scope of the invention.

Claims (15)

1. An indicating panel instrument for measuring electrical parameters having either positive or negative values, comprising a converter comprising a current generator-type amplifier whose outlet terminals are adapted to produce a current directly proportional to the voltage signals applied to its input terminals, the converter generating a measuring voltage indicating the value and sign of the measured electrical parameter and supplying the measuring voltage to a first input of the outlet amplifier, whose outlet terminals, depending on the aforementioned measuring voltage supplied to its first input, generate a measuring current for supplying a milliammeter indicating instrument via a pair of leads, characterised in that the outlet amplifier generates the measuring current in one or the other direction depending on the sign of the measured electrical parameter and the milliammeter instrument (17) has a scale for reading absolute values only, the panel indicating instrument also comprising::
a rectifying bridge (15) disposed between the outlet terminals (12, 13) of the outlet amplifier (1) and the milliammeter instrument (17) in order to rectify the measuring current (lem); transducer means (16) disposed in series with the milliammeter instrument (17) for generating a substantially constant voltage when the measuring current (Im) travels through them;
switch means (18) actuated by a control voltage (Vc) produced at the outlet terminals (12, 13) of the outlet amplifier (1) from the voltage generated by the transducer means (16) and adapted to change to the closed or the open state depending on the sign of the control voltage (Vc);; an oscillator (19) adapted to produce a periodic voltage signal having a frequency much higher than the frequency of variation of the measured electrical parameter and adapted to be connected or disconnected by the switch means (18) to or from a second input (20) of the current amplifier (1), and
sign-indicating means (26) disposed in the reading panel of the ammeter instrument (17) and actuated, via the aforementioned pair of leads (14), by a supply current (lea) generated by the outlet amplifier (1) when the oscillator (19) is connected to the second input (20) of the outlet amplifier (1).

2. An indicator according to Claim 1, characterised in that a first blocking filter (28) is disposed in cascade with the rectifying bridge (15) to prevent the supply current (lea) flowing in the rectifying bridge (15) and a second blocking filter (27) is disposed in cascade with the sign indicating means (26) to prevent the measuring current (Im) flowing in the sign indicating means (26).

3. An indicator according to Claim 2, characterised in that the first blocking filter (28) is an LC band-rejecting filter centered at the frequency of the voltage signal generated by the oscillator (19) and disposed in series with the rectifying bridge (15).

4. An indicator according to Claim 2, characterised in that the first blocking filter (28) comprises a capacitor connected in parallel with the rectifying bridge (15).

5. An indicator according to Claim 2, characterised in that the second blocking filter (27) is a capacitor disposed in series with th sign indicating means (26).

6. An indicator according to Claims 1 and 2, characterised in that the transducer means (16) comprise a
Zener diode disposed so that the measuring current (Im), rectified by the rectifying bridge (15), travels through it from its cathode terminal to its anode terminal.

7. An indicator according to Claims 1 and 2, characterised in that the sign indicating means (26) comprise light indicators.

8. An indicator according to Claim 7, characterised in that the sign indicating means (26) comprise at least one light emission diode (LED).

9. An indicator according to Claim 8, characterised in that the sign indicating means comprise two (LED) diodes.

10. An indicator according to Claim 7, characterised in that the sign indicating means (26) comprise an incandescent lamp.

11. An indicator according to Claims 1 and 2, characterised in that the switch means comprise a field effect transistor (FET) disposed in the source-drain section so as to connect the oscillator (19) to the second input (20) of the outlet amplifier (1), whereas the gate terminal of the (FET) is connected to as to sense the sign of the control voltage (Vc).

12. An indicator according to Claims 1 and 2, characterised in that the sign indicating means (26), the rectifying bridge (1 5), the blocking filters (27, 28) and the transducer means (16) are all in the container of the milliammeter of the instrument (17).

13. An indicator according to Claims 1 and 2, characterised in that the oscillator (19) and the switch means (18) are disposed inside the converter.

14. An indicator according to Claims 1 and 2, characterised in that the frequency of the voltage signal generated by the oscillator is about 5KHz.

15. -An indicator substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

GB7925895A
1978-07-27
1979-07-25
Determi66ng absolute value and polarity of electrical parameters

Expired

GB2031165B
(en)

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

IT2619478A

IT1097432B
(en)

1978-07-27
1978-07-27

INSTRUMENT PANEL INDICATOR FOR ELECTRICAL SIZES EQUIPPED WITH BRIGHT SIGNAL INDICATORS

Publications (2)

Publication Number
Publication Date

GB2031165A
true

GB2031165A
(en)

1980-04-16

GB2031165B

GB2031165B
(en)

1982-11-10

Family
ID=11218898
Family Applications (1)

Application Number
Title
Priority Date
Filing Date

GB7925895A
Expired

GB2031165B
(en)

1978-07-27
1979-07-25
Determi66ng absolute value and polarity of electrical parameters

Country Status (4)

Country
Link

DE
(1)

DE2930119A1
(en)

FR
(1)

FR2433755A1
(en)

GB
(1)

GB2031165B
(en)

IT
(1)

IT1097432B
(en)

Family Cites Families (2)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

DE1945907C3
(en)

1969-09-11
1973-09-27
Metrawatt Gmbh, 8500 Nuernberg

Circuit arrangement for determining the polarity in a measuring circuit for polarity-independent direct current or direct voltage display

DE2126073A1
(en)

1971-05-26
1972-12-07
Metrawatt Gmbh

Circuit for rectifying direct voltages of alternating polarity and for displaying polarity

1978

1978-07-27
IT
IT2619478A
patent/IT1097432B/en
active

1979

1979-07-25
DE
DE19792930119
patent/DE2930119A1/en
not_active
Withdrawn

1979-07-25
GB
GB7925895A
patent/GB2031165B/en
not_active
Expired

1979-07-26
FR
FR7919320A
patent/FR2433755A1/en
active
Granted

Also Published As

Publication number
Publication date

DE2930119A1
(en)

1980-02-07

IT7826194D0
(en)

1978-07-27

FR2433755A1
(en)

1980-03-14

GB2031165B
(en)

1982-11-10

FR2433755B1
(en)

1983-11-25

IT1097432B
(en)

1985-08-31

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