Device for displaying a parameter value and use thereof

Abstract: In a device (1) for displaying a parameter value, said device (1) comprising at least one row of light-emitting diodes (2, 3, 4) in which each light-emitting diode has a position input and a control circuit (5) with address outputs connected to the position inputs, faults such as a short-circuit etc. can be detected more easily when the address outputs and position inputs are inter-connected in such a way that two adjacent address outputs are connected to two position inputs separated by at least one position input.

Description: The invention relates to a device for displaying a parameter value, said device comprising a first LED bar with at least one row of light-emitting diodes, each light-emitting diode having a specific position in the row and a corresponding position input in the first LED bar for lighting the light-emitting diode when a signal is send to the position input, and a control circuit with address outputs connected to the position inputs via signal lines for selectively sending signals to one or several position inputs for lighting one or several light-emitting diodes, whereby a specific light-emitting diode in the row is lit when a signal is sent from the control circuit to the first LED bar via the address output that is connected to the specific light-emitting diode's position input. Such devices are prior art in a plurality of different application fields for different kinds of indications for example, as disclosed in the catalogue, "AllT mellan himmel och jord", ELFA AB, 1990, nr. 39, page 1051". In general, they comprise one row of light-emitting diodes, also known as a bar graph, and a control circuit to turn on individual light-emitting diodes. For this purpose, the control circuit has address outputs connected to position inputs on the row of light-emitting diodes. One problem is that an undetected fault could occur, e.g. a short-circuit between two lines, since the display does not change very much. The nearest diode neighbour then lights as well, something which is not necessarily interpreted as a fault. In addition, an undetected erroneous indication could have consequences, such as e.g. termination of a process at the wrong point or operation of a process with an incorrect parameter value, such as temperature, etc. The object of the invention is to provide a device, as described above, which provides a clear indication of any faults occurring. The object is achieved according to the invention in that the address outputs of the control circuit and the position inputs of the first bar are connected via the signal lines in such a way that two adjacent address outputs are connected to two position inputs physically separated by at least one position input. Accordingly, display is distorted when a fault occurs so the row of light-emitting diodes shows that a fault is present. Especially when indication is only at the parameter value with one or a few light-emitting diodes and not in the form of an illuminated bar, the special connection between the address outputs and the position inputs ensures that a fault can be quickly identified. Indication only at the parameter value also has the additional advantage of reducing the device's power requirements. A refinement of the device according to the invention is obtained by the display of at least two parameter values in the row of light-emitting diodes, such as a reference value and an actual value, and inclusion in the control circuit of a device for lighting the light-emitting diodes, which display the parameter values, with different symbols, such as continuously lit diodes, diodes lit with different intensities for different parameter values, blinking diodes, different blink rates and/or blinking at different levels for different parameters or different numbers of light-emitting diodes in the symbols. The use of a plurality of different indications in the same row of light-emitting diodes saves space. The different values are distinguished by the use of different symbols, such as continuous lighting at one intensity, blinking on and off, blinking at different intensities, different colours, different numbers of light-emitting diodes in the symbols etc. Equipping the device with a parameter value scale parallel to the row of light-emitting diodes would be appropriate in order for indicating the magnitude of a parameter value. A linear parameter value scale is normally sufficient, but indication in a large parameter value range using one light-emitting diode row may be useful in certain instances. To emphasize a specific interval in this range, it would be advantageous to have a partially high-resolution parameter value scale, i.e. each scale segment or the distance between two light-emitting diodes in the most interesting parameter value intervals corresponds to a smaller value than in intervals in which the same accuracy is not required for the parameter value. In other instances, a non-linear parameter value scale might be more useful, e.g. a logarithmic or quadratic scale. Another refinement of the device according to the invention is obtained in that the first LED bar employs two parallel rows of light-emitting diodes, these light-emitting diodes forming of a matrix with one x coordinate and one y coordinate as position input, the control circuit's address outputs comprising one X coordinate and one Y coordinate, address outputs and position inputs connected via the signal lines so two adjacent X coordinate addresses are connected to two x coordinate positions physically separated by at least one x coordinate position and so two adjacent y oordinate addresses are connected to two y coordinate positions physically separated by at least one y coordinate position. Two rows of light-emitting diodes increases the number of possible symbols which can be displayed simultaneously without any risk of mix-up and without increasing the risk of misinterpreting a fault indication. The matrix system reduces the number of connecting lines between the control circuit and the row of light-emitting diodes. Each X coordinate constitutes e.g. part of an address output or a position input for every individual Y coordinate. The crossing of both X and Y coordinate lines ensures that there is at least one empty row of light-emitting diodes on both sides of the indicated symbol. Analogous to the description above in conjunction with indication of two parameter values, the first parameter value can now be indicated with two adjacent light-emitting diodes which shine at a fixed intensity, and the second parameter value can be indicated with the alternate blinking of two adjacent light-emitting diodes. One advantageous refinement of the device according to the invention is obtained in that the control circuit only lights one light-emitting diode at a time, the time elapsing from the lighting of one light-emitting diode until it re-lights being so brief that the light-emitting diode appears to remain continuously lit, and the intensity with which a light-emitting diode appears to shine depends on how often it is addressed and how long it remains lit in the time interval when addressed. Lighting only one light-emitting diode at a time further reduces power consumption. Control of intensity also ensures that intensity increases and any fault is discovered if a short-circuit should occur between two normally lit diodes. The device according to the invention is not limited to the display of only one parameter, but a plurality of LED bars can be added to the system and controlled by the control circuit. In order to increase the system's reliability even further, it would be advantageous if the control circuit contained a parity check circuit which checked to ensure that the signal generated in the control circuit to light a specific light-emitting diode is correct. The parity check circuit would block the emission of the signal and keep the light-emitting diode turned off if a fault occurred. One advantageous embodiment of the device is as an indicator on a ventilator. The correct display of values is particularly important with a ventilator. The safety of a connected patient depends on the administration of gas at a specific pressure and flow rate, on correct gas composition etc. If any parameter is indicated erroneously and the error is not detected, then there is a risk of staff changing a parameter setting in the belief that the setting is incorrect. This change could have grave consequences for the patient. Parameters have hitherto been displayed with analogue dials or digital numerical displays. Analogue instruments are incapable of displaying many values at the same time. One dial for the actual value and one dial for the reference value or an alarm level are normal. More dials increase the difficulty in making correct readings. In addition, the reference value or alarm level must be set manually on analogue instruments. Digital numerical displays can only indicate one value at a time. So a plurality of displays must be used when a plurality of values have to be displayed or the displays must be resettable to permit indication of other values. Moreover, a fault in the indication device could result in the display of an erroneous numerical value. A break in one line could cause e.g. an 8 to be displayed as a 0. With use of the device according to the present invention, a plurality of values can be indicated and read off easily and simultaneously, since the risk of erroneous indications has been minimized. A description in conjunction with the four Figures describes one embodiment of a device according to the invention. Fig. 1 shows the device built into a ventilator; Fig. 2 shows a light-emitting diode segment in the device; Fig. 3 shows the light-emitting diode segment in matrix form with position and address connections; and Fig. 4 shows the control panel of a ventilator in which the device according to the invention has been installed. In the case of ventilators, obtaining information on e.g. pressure and volume must be fast and easy. The information must be readily accessible, and detection of any faults must be simple. Fig. 1 shows a device 1 for this purpose. Device 1 comprises a first light-emitting diode bar 2 for indication of pressure, a second light-emitting diode bar 3 for low-resolution indication of volume, a third light-emitting diode bar 4 for high-resolution indication of volume, and a control circuit 5. The control circuit 5 is connected to the three light-emitting diode bars 2, 3, 4 by an X coordinate address data bus 6 and a Y coordinate address data bus 7 which are described in greater detail below. A multiplexer 8 supplies the control circuit 5 with parameter values for pressure and volume via the data bus 101. The multiplexer 8 sends the two actual values to the ventilator as well as the reference value and alarm levels set. Data flow to the multiplexer 8 is indicated by a data bus 102. In the control circuit 5, the data bus 101 is connected to a microprocessor 11 in which each parameter value is processed and transformed into a data instruction which consists of two bytes, one odd and one even, for each light-emitting diode which is to be lit, and contains the address, intensity level and parity check bits. The data instruction is sent from the microprocessor 11 to a double port RAM 12 (DPR) via the data bus 104. The data instruction is fetched from the DPR's 12 data output in two stages and controlled by a pulse sender 14. The pulse sender 14 controls the switching between the two addresses for the odd and even byte respectively in the DPR 12 and transmissions to a first and second intermediate level memory 15, 16. A counter 13 controls the transmission of each new data instruction from the DPR 12. The counter 13 and pulse sender 14 are clocked at a rate of e.g. 15,625 Hz, i.e. a period duration of 64 µs. Clocking is designated in the Figure with Cl. When the counter 13 addresses data transmission from the DPR 12 at the beginning of a period via the data bus 103, the pulse sender 14 emits a negative pulse with a duration of 8 µs through a first signal line 105 and a negative pulse with a duration of 4 µs through a second signal line 106. The first signal line 105 connects the pulse sender 14 to the microprocessor 11, the DPR 12, the first intermediate level memory 15 and a third intermediate level memory 17. The second signal line 106 connects the pulse sender 14 to the DPR 12 and the second intermediate level memory 16. The connection between the pulse sender 14 and the microprocessor 11 is to enable the microprocessor to synchronize transmission of the data instruction to the DPR 12 via the data bus 104 When the positive flank of the signal in the second signal line 106 appears, i.e. 4 µs into the period, the even byte from the DPR's 12 data output is transmitted via the data bus 107 to the second intermediate level memory 16 which is also activated by the positive flank. The DPR is simultaneously re-switched in order to emit the odd byte from its data output. 8 µs into the period, the positive flank of the signal appears at the first signal line 105, and the odd byte is sent to the first intermediate level memory 15 at the same time as the four lowest bits in the second intermediate level memory 16 are sent to the third intermediate level memory 17 via the data bus 108. These four bits, plus the sixth bit in the odd byte, constitute the X coordinate information, whereas the four highest bits in the even byte constitute the intensity information. The third intermediate level memory is connected via a data bus 109 to a parity check circuit 18 and an addressing circuit 19 to which the four bits are sent. The odd byte in which the five lowest bits constitute the Y coordinate information is sent to the parity check circuit 18, the sixth bit, constitutes a part of the X coordinate information, as noted above, and the two highest bits constitute special parity bits used for the parity check. If a parity error occurs, the parity check circuit 18 sends a signal via the signal line 111 to the microprocessor 11 and to the addressing circuit 19. All light-emitting diodes will then be turned off. This prevents the overloading and destruction of individual light-emitting diodes if the same light-emitting diode is addressed continuously due to some fault in the data instruction. The light-emitting diodes re-light as soon as all the information in the DPR 12 is correct. The four bits in the even byte which constitute the intensity information are sent from the second intermediate level memory 16 via a data bus 112 to an intensity pulse former 20. Intensity information is transformed in the intensity pulse former 20 into a pulse whose width designates the time the light-emitting diode is to be lit during the period, i.e. pulse width can vary from 0 to 56 µs, 56 µs constituting maximum intensity. The intensity pulse is sent to the addressing circuit 19 via a signal line 113. X and Y coordinate information is read in the addressing circuit 19, and a signal is sent to the respective coordinate address bus 6, 7 to light the addressed light-emitting diode for the duration of the intensity pulse. When this period has elapsed, the counter 13 increments one step so as to address the next byte pair identifying a new light-emitting diode. With e.g. a 7-bit counter, 64 light-emitting diodes can be addressed in one cycle, the first light-emitting diode thereafter being addressed once again. The cycle period could also consist of six or eight or some other number of bits, and one and the same light-emitting diode could be addressed many times during a cycle in order to increase the intensity. A parameter value scale 22 is parallel to each light-emitting diode bar 2, 3, 4 to permit the values for pressure and volume respectively to be read off. As Fig. 1 shows, the light-emitting diode bars 2, 3, 4 consist of a number of light-emitting diode segments 9. Fig. 2 shows one of these light-emitting diode segments 9. The light-emitting diode segment 9 consists of forty light-emitting diodes 10, each of which with a unique position coordinate in the light-emitting diode segment 9, as shown in Fig. 2. The light-emitting diodes 10 are sub-divided into ten y coordinate groups, y0 - y9 each of which with four x coordinates, x0 - x3. In principle, each individual light-emitting diode 10 could have its own signal line, but the total number of lines can be reduced with a coordinate system, i.e. from forty to fourteen lines in this instance. Fig. 3 shows the light-emitting diode bar 9 in matrix form to illustrate the manner in which fault indication is performed according to the invention. The positions are indicated with lower case letters and addresses with upper case letters. Every crossing 21 of two position lines corresponds to a light-emitting diode, and every combination of an x and a y coordinate constitutes a position input for the light-emitting diode at the intersection of the two coordinates. As Fig. 3 shows, an address coordinate X0, for example, has been connected to the position coordinate x2, address coordinate X1 to position coordinate x0, X2 to x3 etc. If a short-circuit should occur between two address coordinates, e.g. Y3 and Y4, a signal on either of the lines will also lead to transmission of the signal to the second line via the short-circuit point. A signal to light a light-emitting diode via the address coordinate X0Y4 also results in a signal with the address coordinate X0Y3. In Fig. 2, the position coordinate x2y8, which is lit by the address coordinate X0Y4, has been marked. The address coordinate X0Y3 lights the position coordinate x2y6, also marked in Fig. 2 which shows that there are three rows of light-emitting diodes between the two positions. This discrepancy would be quickly interpreted as a fault. In principle, cross-connection of the address and position coordinates can be achieved in any way. It is essential that two adjacent address coordinates must not be connected to two adjacent position coordinates. As Fig. 1 shows, the first light-emitting diode bar 2 consists of six light-emitting diode segments 9, and each of the second and third light-emitting diode bars 3, 4 consists of four light-emitting diode segments 9, i.e. a total of fourteen light-emitting diode segments 9 which are addressed by the control circuit 5. If each light-emitting diode segment 9 were to be addressed individually, 14 x 14 lines would be required (Fig. 3 shows that one light-emitting diode segment 9 requires fourteen lines), i.e. 196 lines, 140 of which Y address lines and 56 X address lines. By having the same coordinates address a plurality of light-emitting diode segments 9, the number of lines can be reduced. With e.g. three groups of ten Y address coordinates (Y0-Y9, Y10-Y19, Y20-Y29) and five groups of four X address coordinates (X0-X3, X4-X7, X8-X11, X12-X15, X16-X18), fifteen unique sets of addresses can be combined by having each X address coordinate group constitute a part of the address in combination with each Y coordinate group. This is sufficient for addressing any individual light-emitting diode in one of fifteen light-emitting diode segments. each comprising forty light-emitting diodes. In this example, there are fifty lines from the control circuit 5 , thus a 146-line reduction. Fig. 4 shows the front of a control unit 23 for the ventilator in which the device according to Figs. 1-3 is installed. The control unit 23 is divided into different function fields 28-34 with setting knobs 24, light-emitting diode displays 25, setting indicators 26, alarm indicators 27 and light-emitting diode bars 2, 3, 4. The function of the various designated function fields 28-34 is as follows: the ventilator's operating mode is set in function field 28, patient type, i.e. whether the patient is an adult, child or infant, is set in function field 29, oxygen concentration is set in function field 30, pressure is set in function field 31, flow rate is set in function field 32, volume is set in function field 33 and function field 34 indicates errors which can occur in the ventilator.

Claims: A device (1) for displaying a parameter value, said device comprising a first LED bar (2) with at least one row of light-emitting diodes (10), each light-emitting diode (10) having a specific position in the row and a corresponding position input in the first LED bar (2) for lighting the light-emitting diode (10) when a signal is sent to the position input, and a control circuit (5) with address outputs connected to the position inputs via signal lines (6, 7) for selectively sending signals to one or several position inputs for lighting one or several light-emitting diodes (10), whereby a specific light-emitting diode (10) in the row is lit when a signal is sent from the control circuit (5) to the first LED bar (2) via the address output that is connected to the specific light-emitting diode's (10) position input, characterized in that the address outputs of the control circuit (5) and the position inputs of the first LED bar (2) are connected via the signal lines (6, 7) in such a way that two adjacent address outputs are connected to two position inputs physically separated by at least one position input. A device according to claim 1, characterized in that the control circuit (5), to indicate the parameter value, only sends a signal to the diode/diodes (10) corresponding to the parameter value. A device according to claim 1 or 2, characterized in that at least two parameter values are displayed in the first LED bar (2), such as a reference value and an actual value, and in that the control circuit (5) comprises a device (11;20) for lighting the light-emitting diodes (10) which display the parameter values with different symbols, such as continuously lit diodes, diodes lit with different intensities for different parameter values, blinking diodes, different blink rates and/or blinking at different intensity levels for different parameters. A device according to any of the above claims, characterized in that a parameter value scale is installed parallel to the first LED bar (2). Device according to claim 4, characterized in that the parameter value scale is non-linear. Device according to any of the claims 2 to 5, characterized in that the first LED bar (2) employs two parallel rows of light-emitting diodes (10), these light-emitting diodes (10) forming a matrix with one x coordinate and one y coordinate as position input, the control circuit's (5) address outputs comprising one X coordinate and one Y coordinate, address outputs and position outputs connected via the signal lines (6, 7) so two adjacent X coordinate addresses are connected to two x coordinate positions physically separated by at least one x coordinate position and so two adjacent Y coordinate addresses are connected to two y coordinate positions physically separated by at least one y coordinate position. Device according to claim 6, characterized in that the first parameter value is indicated with two adjacent light-emitting diodes (10) lit with a fixed intensity, and the second parameter value is indicated with alternate blinking of two adjacent light-emitting diodes (10). Device according to any of the above claims, characterized in that the control circuit (5) only lights one light-emitting diode (10) at a time, the time elapsing from the lighting of one light-emitting diode (10) until it is re-lit being so brief that the light-emitting diode (10) appears to remain continuously lit, and that the intensity with which a light-emitting diode (10) appears to shine depends on how often it is addressed and how long it remains lit in the time interval when addressed. Device according to any of the above claims, characterized in that the device comprises a least one additional LED bar (3) with at least one row of light-emitting diodes (10), separate from the first LED bar (2), to indicate the value of a second parameter, the control circuit (5) controlling both the first LED bar (2) and the additional LED bar (3). Device according to any of the above claims, characterized in that the control circuit (5) comprises a parity check circuit (18) which checks to ensure that the signal generated in the control circuit (5) to light a specific light-emitting diode (10) is correct, the parity check circuit blocking the emission of the signal so the light-emitting diode (10) remains off if a fault occurs. Use of a device according to any of the claims above in a ventilator. Use according to claim 11 to indicate one or more of the parameters pressure, flow, volume and gas concentration.

Inventors: CEWERS GOERAN, IDERUP MATS, OLSSON SVEN-GUNNAR, RYDGREN GOERAN, CEWERS, GOERAN, IDERUP, MATS, OLSSON, SVEN-GUNNAR, RYDGREN, GOERAN, Cewers, Göran, Rydgren, Göran
Applicants: SIEMENS AG, SIEMENS ELEMA AB, SIEMENS AKTIENGESELLSCHAFT
Application year: 1992
Main classification: G01D13
IPC codes: G01R13, G09G3