GB2268819A - Determining nominal resistance and measuring current for temperature detection of electromagnetic coils. - Google Patents
Determining nominal resistance and measuring current for temperature detection of electromagnetic coils. Download PDFInfo
- Publication number
- GB2268819A GB2268819A GB9313179A GB9313179A GB2268819A GB 2268819 A GB2268819 A GB 2268819A GB 9313179 A GB9313179 A GB 9313179A GB 9313179 A GB9313179 A GB 9313179A GB 2268819 A GB2268819 A GB 2268819A
- Authority
- GB
- United Kingdom
- Prior art keywords
- voltage
- electromagnetic coil
- temperature detection
- current
- constant current
- Prior art date
- 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
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/22—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of impact or pressure on a printing material or impression-transfer material
- B41J2/23—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of impact or pressure on a printing material or impression-transfer material using print wires
- B41J2/30—Control circuits for actuators
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
- G01K7/20—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Resistance Or Impedance (AREA)
- Dot-Matrix Printers And Others (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The nominal resistance value and the measurement current for temperature detection of electromagnetic coils (5), especially in matrix print heads (1), are determined on the basis of a measuring circuit including a first reference resistor (22), in which a voltage drop in the electromagnetic coil may be measured by means of a constant current. More accurate measurement values can be obtained by computing the voltage present at a second reference resistor (25) or the voltage drop at a electromagnetic coil (5) with a predetermined constant current as a value for a matrix print head (1), the known ohm resistance of which defines the type thereof in terms of the number of printing pins. <IMAGE>
Description
A METHOD AND CIRCUIT FOR DETERMINING THE NOMINAL RESISTANCE AND THE
MEASURING CURRENT FOR TEMPERATURE DETECTION OF ELECTROMAGNETIC COILS This invention relates to a method and circuit for determining the nominal resistance and the measuring current for temperature detection of electromagnetic coils, and in particular to such a method and circuit for use with matrix print heads.
German Patent Application 3914217 describes determination of nominal resistance value and measurement current f or temperature detection of electromagnetic coils, especially in matrix print heads, by use of a measuring circuit in which the voltage drop in an electromagnetic coil is measured by means of a constant current. However, measurement is carried out exclusively in charging intervals. The known process has otherwise proven itself useful.
It is amongst the objects of the invention to provide a method which allows even more accurate values to be obtained with the known method.
There is provided, according to the invention, a method, and corresponding circuitry, for determining the nominal resistance value and the measurement current for temperature detection of electromagnetic coils within a device, on the basis of a measuring circuit in which a voltage drop in an electromagnetic coil may be measured by means of a constant current, wherein the voltage at a reference resistor or the voltage drop at the electromagnetic coil is computed with a predetermined constant current as a value for the device, known resistance values for which define the device type.
The advantages of this include especially the fact that not only is the device type recognisable, but also sensitive adjustments may be undertaken at the device and temperature measurement of the order of 3'C is achievable.
Circuitry, in a particularly advantageous embodiment of the invention includes at least one voltage divider and one current limiting circuit connected to a voltage measuring unit, in turn connected to a microprocessor, for 2 constant current formation. Moreover each individual electromagnetic coil is connected in an independent current circuit to the voltage measuring unit and the voltage drop values of each individual electromagnetic coil is individually retrievable. Such circuitry, which in practice forms a thermo-sensor, may be realised by an integrated circuit.
In a further embodiment a reference resistor is arranged in a current circuit connected to the voltage measuring unit and all the electromagnetic coils lie at the same supply voltage. In this way, individual scanning of the electromagnetic coils may be performed easily from a practical and an economical point of view.
The reference resistor is, in effect, a second one, a first being included in the basic measuring circuit.
The device is very preferably a matrix print head. A number of types of print head, which differ in terms of the number of pins, and hence coils, are known.
The invention will now be described with reference to the accompanying drawings:- Figure 1 is a partial cross-section of a matrix pin print head; and Figure 2 is a circuit block diagram illustrating the invention.
The circuit shown in Figure 2 is associated with the matrix print head 1 shown in Figure 1 and is connected therewith. In the print head 1, a magnet armature 3 is associated with each printing pin 2, and a magnet yoke 4 and an electromagnetic coil 5 surround a magnet yoke arm of magnet armature 3. The number of pins 2, and hence coils 5, depends on the type of print head 1 and may be, for example, 6, 9, 12, 18, 21 or 24.
The circuit includes a clock line 7 and a data bus 8 connected to a voltage measuring unit 6 (integrated circuit). Further signal lines 9 connect the voltage 3 measuring unit 6 with a microprocessor 27.
A f irst voltage divider 10 and a second voltage divider 11 are connected to the voltage measuring unit 6, each of which consists of two resistors, 12, 13 and 14, 15.
A current limiting circuit 16, comprising an operational amplifier 17, resistors 18 and 19, a stabilising capacitor 20, a transistor 21 with a first reference resistor 22 and a protective resistor 23, is further connected to the voltage measuring unit 6.
The voltage measuring unit 6 forms, together with an electromagnetic coil 5, a free-wheeling diode 24 and the current limiting circuit 16, a closed circuit. A second reference resistor 25 is also connected to the voltage measuring unit 6.
The voltage drop at the second reference resistor 25 or one of the electromagnetic coils 5, the number of which may be 6, 9, 12, 18, 21 or 24, permits the respective ohm resistance value to be calculated, with a predetermined constant current of the current limiting circuit 16, which ohm resistance value will correspond to a particular matrix print head type, i.e. one with 6, 9, 12, 18, 21 or 24 pins. Thus, the microprocessor 27 may at any time determine the type of the matrix print head, and also set the following operational data as appropriate for the particular print head: the charging time, the current value and the measurement current for temperature detection.
The single variable value in this process is the measurement current, which is set by the microprocessor 27 via a D/A converter 26.
A possible further circuit variant would be alteration not of the measurement current, but of the reference voltages V2 and V1 (registered in the voltage measuring unit 6).
The circuit, which is shown, then has the advantage that the voltage reference values difference, V2 minus V1, may be kept as small as possible, e.g. to the minimum of 0.5 volts, such that as large as possible a voltage 4 resolution is achieved. For the "cold" and "hot" state of the electromagnetic coils 5 to be measured or their resistance, two measuring ranges are used, i.e. two measurement currents of different magnitudes.
Claims (5)
1. A method for determining the nominal resistance value and the measurement current for temperature detection of electromagnetic coils within a device, on the basis of a measuring circuit in which a voltage drop in an electromagnetic coil may be measured by means of a constant current, wherein the voltage at a reference resistor or the voltage drop at the electromagnetic coil is computed with a predetermined constant current as a value for the device, known resistance values for which define the device type.
2. Circuitry for determining the nominal resistance value and the measurement current for temperature detection of electromagnetic coils within a device, with a measuring circuit in which a voltage drop in an electromagnetic coil may be measured by means of a constant current, comprising a voltage measuring unit wherein, for constant current formation, at least one voltage divider and a current limiting circuit are connected to the voltage measuring unit which is connected to a microprocessor, wherein each electromagnetic coil is connected to the voltage measuring unit in an independent circuit and the voltage drop values of each electromagnetic coil may be retrieved individually.
3. Circuitry as claimed in Claim 2, wherein a reference resistor is connected to the voltage measuring unit and all the electromagnetic coils are at the same supply voltage.
4. A method substantially as hereinbefore described and illustrated in the accompanying drawings.
5. Circuitry substantially as hereinbefore described and illustrated in the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19924221261 DE4221261A1 (en) | 1992-06-26 | 1992-06-26 | Method and circuit arrangement for determining the nominal resistance value and the measuring current for the temperature detection of electromagnetic coils, in particular in matrix print heads |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9313179D0 GB9313179D0 (en) | 1993-08-11 |
| GB2268819A true GB2268819A (en) | 1994-01-19 |
| GB2268819B GB2268819B (en) | 1996-02-28 |
Family
ID=6462050
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9313179A Expired - Fee Related GB2268819B (en) | 1992-06-26 | 1993-06-25 | A method and circuit for determining the nominal resistance of electromagnetic coils |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE4221261A1 (en) |
| FR (1) | FR2692992A1 (en) |
| GB (1) | GB2268819B (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5042375A (en) * | 1989-04-27 | 1991-08-27 | Mannesmann Aktiengesellschaft | Device for temperature control of a print head or of a hammer block including an electromagnetic coil |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0559161B1 (en) * | 1992-03-06 | 1998-06-10 | Seiko Epson Corporation | Drive coil overheating protection for wire dot printer |
-
1992
- 1992-06-26 DE DE19924221261 patent/DE4221261A1/en not_active Ceased
-
1993
- 1993-06-18 FR FR9307385A patent/FR2692992A1/en active Pending
- 1993-06-25 GB GB9313179A patent/GB2268819B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5042375A (en) * | 1989-04-27 | 1991-08-27 | Mannesmann Aktiengesellschaft | Device for temperature control of a print head or of a hammer block including an electromagnetic coil |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2692992A1 (en) | 1993-12-31 |
| GB2268819B (en) | 1996-02-28 |
| GB9313179D0 (en) | 1993-08-11 |
| DE4221261A1 (en) | 1994-01-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000625 |