JPS5824001B2 - Flat electrical resistor with high precision resistance value - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flat electrical resistor having a highly accurate and adjustable resistance value and a method for manufacturing the same.

As is already known, high-precision resistors are produced by etching a thin sheet of metal or alloy by electrolytic processing or ion bombardment to obtain a large number of electrically resistive filaments separated by grooves or slits. can be manufactured.

This type of resistor and its manufacturing method are both disclosed in Application No. 7607889 filed on March 18, 1976 in the name of the present applicant.
No. 7,617,269 filed June 8, 1976.

The method described above makes it possible to obtain a resistive circuit with a tortuous profile and substantial length.

The electrically resistive fibers etched into thin sheets of metal or alloys have a thickness of not more than a few microns, so that these resistors have very high resistance values per unit area.

After manufacturing in mass production, these resistors must be adjusted to a precise resistance value, sometimes exceeding the initial value by 50 to 150%.

In the known method, this resistance value is adjusted by means of a cutout formed between the edge of the resistor and a groove separating the drowsiness resistance filaments, the purpose of which cutout is to adjust the resistance value. In order to increase the number of fibers in the circuit, a predetermined number of said fibers can be inserted into the circuit.

Adjusting this resistance by removing is a very delicate operation;
This must actually be done by grinding or scraping with a sand jet or laser beam under a microscope.

Moreover, this operation takes a very long time.

This is because each resistor has a large number of electrically resistive fibers, so it is often necessary to carry out a very large number of deletion operations.

For example, for a resistor with an initial value of 23.OMEGA., it is necessary to make a 102 cut on the edge of the resistor to bring the resistance value to 42.OMEGA.

The object of the invention is to provide a flat electrical resistor whose resistance value can be matched more conveniently and quickly than in the case of the resistors described above.

The flat electrical resistor contemplated by the present invention is:

It comprises a thin sheet of metal or alloy deposited or bonded onto a support and a series of electrically resistive filaments separated by strips in such a manner as to define a tortuous electrically resistive circuit.

The resistor comprises a series of electrical resistance circuits shorted by conductive strips constructed of the sheet metal or alloy.

According to the present invention, the resistor has an increment ΔR of resistance value RTn when n combined resistance circuits are connected in series and (n−
1) It has the characteristic that the ratio between the resistance value RTn-t of the resistor when the combined resistance circuits are connected follows the following relationship.

That is, here Un is Cauchy's criterion for absolute convergence (According to Modern Analysis, Whittaker and Watson, University Press Cambridge Publishing, 2-3)
nth absolutely convergent series that satisfies (see Section 5, page 21)
The next term is ΔR=RT−RTn−1.

In order to match the final resistance value of the resistor, the cutout is formed in the sheet and is intended to insert in series with the remainder of the circuit a combined resistor circuit whose resistance value corresponds to the desired value of the resistor.

It will be seen that when the increment ΔR follows the above relationship, the number of cuts that have to be made in the sheet to adjust the value of the resistor can be significantly reduced.

In a preferred embodiment of the invention, K is an adjustable numerical coefficient having a value less than one.

The present invention also relates to an electrical resistor having a highly accurate resistance value, as described above, in which a thin plate of metal or alloy is adhered to or bonded to a substrate, which is usually It has a thermal conductivity coefficient equal to or greater than that of alumina and sufficient to prevent excessive temperature gradients between the resistive portion of the circuit and the portion that remains shorted.

The present invention also includes:

The present invention relates to a method of adjusting the resistance value of the aforementioned electrical resistor.

In the method, a cutout is formed in a conductive strip that shorts the combined electrical resistance circuit.

The method essentially consists in first forming a cutout of this type in a conductive strip corresponding to an assembled circuit in such a way that the increase in resistance is as close as possible to the desired adjustment value. .

This adjustment is next. This is accomplished by sequentially inserting the combined circuit into the circuit and adding progressively smaller increases in resistance value.

In this way, only one cutout is formed for each combined resistive circuit, so that the maximum number of cutouts formed does not exceed the number of circuits.

Furthermore, due to the fact that each combined circuit is composed of multiple parallel resistance fibers that typically span a fairly large width, the deletion operation is performed with a lower degree of precision than in traditional methods. It only requires

At the same time as the different electrical resistance circuits, a slit is formed in the aforementioned long piece by etching extending between the reference numeral and the corresponding combined resistance circuit to adjust the final resistance value of the resistor. It will also be appreciated that it is advantageous for the cutout to be formed between the side of the sheet and the reference numeral above.

The numbers greatly facilitate the identification of the combined circuit to be inserted into the circuit and the formation of the deleted parts.

Other distinguishing features and advantages of the invention will become apparent from the following description, and reference may be made to the accompanying drawings, which are given by way of example and not in a limiting sense, in which: FIG.

FIG. 1 is a schematic plan view of an electrical resistor obtained according to the present invention, and FIG. 2 is a partially enlarged view of the resistor in FIG. 2 shows the combined electrical resistance circuit connected to the rest of the circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the accompanying drawings there is shown a flat electrical resistor obtained from a rectangular thin plate 10 of an alloy, such as a nickel chromium alloy, several microns thick.

The electrical resistance circuit of the resistor is itself well known.

It is preferably obtained by electrolytic machining or ion bombardment through a mask having windows defining the outline of the electrical circuit to be etched onto the sheet 10.

The sheet 10 is deposited or bonded onto an electrically insulated support (not shown) having a thermal conductivity coefficient equal to or greater than that of 96% pure alumina.

For clarity of the drawing, the electrical resistance threads 11 are shown in FIG. 1 between parallel lines representing grooves or slits 12 of the resistor.

The practical form of the electrical resistance circuit section is shown in FIG.

As shown in FIG. 1, the resistor includes a plurality of parallel strands, the strands having a substantial length.

Therefore, a tortuous electrical circuit having a high resistance value per unit area is formed.

Sheet 10 includes a series of combined resistive circuits AI, A2°A3; B, , B2 . B3; C1, C2,...c
8' DI.

B2. ...D, and in this circuit, the original resistance value increment ΔR follows the following relationship.

Here, Un is the nth term of the absolute convergence series that satisfies Cauchy's absolute convergence criterion, and △R=RT −
RTn-1, RTn is the resistance value of n resistance circuits combined, and RTn- is the resistance value of (n-1) resistance circuits combined.

From FIG. 1, circuit A1 has more fibers 11 than circuit A2.
One circuit A2 also has another circuit A3 . B□.

It is clear that it has more filaments 11 than B2 and the like.

The convergence series can be: where K is an adjustable numerical coefficient with a value less than 1.

This convergence series may be a geometric sequence.

Further from FIG. 1, reference number 13° 14.1 during manufacture
The long pieces shown by 5, 16, 17, and 18 are thin plates 1.
0 sides A, B, C, D and each combined circuit A1.
...2B1. . . , C1, .

As a result, the resistor obtained after manufacturing is assembled into a circuit A
I,...,B1. . . 2C1, . . . has an initial resistance RTo constituted by the resistance values of all the electrical resistance fibers that do not form the portion Dl.

A combined circuit A1. for adjusting the resistor to the desired resistance value. ...2B1. ...2C1 or Dl with the resistance value closest to the desired adjustment value is first inserted into the circuit, and the adjustment is completed by inserting into the circuit the combined circuits with progressively lower resistance values. be done.

This operation is accomplished by forming a cutout 19 (shown in FIG. 2) in the conductive strip designated by reference numerals 13, 14, 15, 16, 17, or 18.

The cutout extends between the sides A or B, C, D of the laminate 10 and the corresponding combined circuit A3.

The deletions, as indicated by the reference numeral 19, are produced in a manner known per se, for example by scraping with a sharp tool, a sand jet or a laser beam.

In order to allow the resistor to be adjusted over a fairly wide range of resistance values, the ratio RTn/RT1 is usually used.

A multiplication factor M equal to (RTn is the resistance value obtained when all combined circuits are inserted into the circuit) is selected and is made to be around 2.

As also shown in FIGS. 1 and 2, reference numerals 1,
2, 3. . . 9 and the slit 20 (see FIG. 2) extending between said reference numeral and the corresponding associated circuit A3, the different electrical resistance circuits A1. ...2B1. ...2C1,...

Dl,... At the same time, the long pieces 13, 14, 15° 16
．． Etched to 17 or 18.

To adjust the resistor, the combined circuit A1. which is to be inserted into one circuit. ..., B1. ..., C1゜...
・2D1. . . , and then connect the deleted portion indicated by reference number 19 in FIG. Just form it in between.

Note that the resistance circuits D1°B2.
B3. ..., D, to form a deleted part.

Resistance parts e, f, g, ...2 in Fig. 1, respectively
m is cut and electrical cutting is performed.

In the embodiment of FIG. 1, the combined electrical resistance circuit A
I,...yBy...2C...2D1.・・・・・・
... is 1 1y Four separated rectangular blocks 21 and 22 arranged along each of the sides A, B, C, and D of the thin plate 10
, 23, 24.

This arrangement ensures that the verification of the combined circuit is extremely easy.

A numerical example of 2.3 is shown below.

Example 1 This example, without any intention of limitation, illustrates how a resistor tuning law is established according to the method of the invention.

This resistor is characterized in that the number of adjustment points is equal to 23 and the 1 multiplication factor M is equal to 2.

The multiplication factor is the ratio of the resistance value when all points are adjusted to the initial value of the resistor.

The following rules are adopted:

Therefore, if RTo=15KQ, the following table is obtained.

When all the resistors are inserted into the circuit, or in other words when 23 deletions such as 19 are formed, the maximum adjustment resistance is 14,212Ω + 15,000Ω (initial value) - 29,212,11Ω. be.

That is, the multiplication coefficient is 1.9474.

Example 2 In this column the resistor has an initial value RTo of 15Ω.

Assume that it is desired to adjust this value to 25,000Ω±0.1%.

Therefore, the initial value must be increased from 66.51% to 66.83% to fall within the tolerance of ±0.1%.

To this end, the procedure consists first of all in selecting a circuit whose resistance value is as close as possible in percentage to the value desired to be obtained.

In this example, adjustment points A and A2 are each 3
Equal to 3.6% and 22.6%.

Accordingly, cut-out portions such as portion 19 are formed in the manner described above.

The same procedure is used in order &[.

That is, in the case of B1 with 9% hail, and in the case of C2 with 1.4% hail.

This is the case with Dl containing 0.07%.

Therefore, a percentage of 66.67% is obtained.

This result is therefore achieved by forming only five deletions, as indicated by reference numeral 19 in FIG.

If finer adjustments to the resistor values are to be made, additional cuts need to be made to insert into the circuit combined resistors with progressively lower resistance values.

Example 3 (Comparative Example) Example 2 is a resistor formed by a conventional adjustment method.
With the same initial value as in the case of , it is necessary to make 27 cuts in order to obtain a final resistance 25 of Ω±0.1%.

It will be clearly understood that the invention is not limited to the examples described above and that many modifications are possible without departing from the scope and spirit of the invention.

Alternatively, the resistor may be manufactured using a Wheatstone or Kelvin method in a known manner.
vin) by incorporating it into the bridge.

and can be adjusted by using a digital voltmeter.

moreover. Each combined circuit A1. ...yBy...
It is also possible to use a computer in which the resistance values corresponding to . . . , C1° . . . , Dl, .

This can be done using a simple calculation program as follows.

That is, an image of the resistor can be viewed in binocular eyepieces using a digital microdisplay to give the operator an indication of the cut to be made.

or operating an XY table controlled by a computer, with an automatic removal device of a type known per se (sand jet or laser beam).

This is made possible by the fact that the reference numerals of the combined circuits are relatively small in number and large enough not to cause mechanical problems with respect to the guidance of the cutting device.

Furthermore, the reference numeral and the side A of the resistor.

Because of the metal long piece that exists between B, C or D,
Adjustment of the resistance can also be achieved by simple subtraction between the number under consideration and the adjacent edges of the resistor.

As a result, the invention makes it possible to considerably facilitate the adjustment of the resistance value of a resistor of the type described above.

Furthermore, the invention makes it possible to reduce any risk of errors, so that the reliability of the accuracy obtained in this way is statistically much greater than with conventional methods.

[Brief explanation of the drawing]

1 is a schematic plan view of an electrical resistor obtained according to the invention, and FIG. 2 is a partially enlarged view of the resistor of FIG. 1, after cutting along the edge of the thin plate. shows a combined electrical resistance circuit connected with the rest of the circuit. 10... Thin plate, 11... Electric resistance fiber, 12... Groove or slit, 13, 14,
15,16゜17.18...Long piece part, 19...
...Deleted part, 20...Slit, 21,
22, 23, 24...Long rectangular blocks.

Claims (1)

[Scope of Claims] 1. A flat plate electrical resistor having a highly accurate resistance value, the resistor having an adjustable resistance value and comprising a metal or The resistor is constructed of a thin sheet of alloy and includes a series of drowsiness-resistance strands separated by grooves to define a tortuous electrical resistance circuit, the resistor being a conductive layer formed by the metal or alloy of the sheet. It is composed of a series of electrical resistance circuits short-circuited by long pieces, and the increment of resistance value ΔR when the combined resistance circuits are connected in series and (n-1) combined resistance circuits are connected. The ratio between the resistance value RTn-1 of the resistor and the resistance value RTn-1 of the resistor when And ΔR=RTn-RTn-t. Flat electrical resistor with high precision resistance value. 2. A resistor according to claim 1. and K is an adjustable numerical coefficient having a value less than 1. 3. A resistor according to claim 1. The slats are square or rectangular, and the combined electrical resistance circuit is divided into four separate rectangular blocks located together along each side of the slats. Resistor. 4. A resistor according to claim 3. The resistance circuit of each block is less than or equal to 9;
and a resistor indicated by a number etched into a conductive strip located between the assembled circuit and the adjacent side of the sheet. 5% The resistor according to claim 1. A resistor in which the support to which the resistive sheet is applied or bonded has a thermal conductivity coefficient equal to or greater than that of 96% pure alumina. 6 A flat electrical resistor with a highly accurate resistance value, which resistor has an adjustable resistance value and is composed of a thin plate of metal or alloy bonded to or bonded to a support. , and comprising a series of electrically resistive strands separated by grooves to define a tortuous electrically resistive circuit, the resistors being short-circuited by conductive strips formed of the metal or alloy of the sheet. The increment △R of the resistance value when the combined resistance circuits are connected in series and the resistance value of the resistor when (n-1) combined resistance circuits are connected are: The ratio with the resistance value RTn-1 has the following relationship: where Un is the nth term of the absolute convergence series that satisfies Cauchy's absolute convergence criterion. and ΔR=RTn-RTn-t. A method for manufacturing a flat electrical resistor having a high precision resistance value, wherein a cut-out portion is formed in the conductive long piece to short-circuit an assembled electrical resistance circuit, the cut-out portion is first formed into a resistor. The adjustment is made in the conductive strip corresponding to the combined circuit such that the increase in value is as close as possible to the desired adjustment value, and the adjustment provides a combination circuit that provides progressively smaller increases in resistance value. Including the process of adjusting the resistance value that is sequentially inserted into the circuit.
A method for manufacturing a flat electrical resistor having a highly accurate resistance value.