DISPLAY VERIFIER

• US 3,866,171 A
• Filed: 01/18/1974
• Issued: 02/11/1975
• Est. Priority Date: 01/18/1974
• Status: Expired due to Term

• Current Assignee: Toledo Scale Corporation 350 W Wilson Bridge RD Worthington Oh
• Original Assignee: Richard C. Loshbough
• Inventors: Loshbough, Richard C.
• Primary Examiner(s): Gruber, Felix D.
• Assistant Examiner(s): Dildine, Jr., R. Stephen
• Application Number:
  US05/434,606
• Time in Patent Office: 389 Days
• Field of Search: 235/153A,153AC 315/129 340/146.1R,146.1C,324R,336
• US Class Current: 714/819
• CPC Class Codes: G06F 11/162 Displays
• CPC Class Codes: G06F 11/2215 to test error correction or detection circuits
• CPC Class Codes: G06G 7/195 using electro- acoustic elements
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/04 for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions
• CPC Class Codes: H03K 21/08 Output circuits

Abstract

An improved circuit for verifying that a digital display and particularly a display formed from seven-segment gas discharge indicators is operating correctly. Cathodes of the indicator segments are driven from decoded BCD display data. The cathode of each segment is connected through a monitoring circuit to a 7-bit comparator where the actual operation of the segment is compared with the original display data. An error signal is generated if any segment fails to illuminate or extinguish in accordance with the data or if a segment is open or short-circuited. A test switch is provided for temporarily simulating an error to produce an error signal for test purposes. The circuit is adaptable for use with multiple digit displays wherein the display data is provided to the individual digits by means of multiplexing.

Claims

1. A character display for operation from a data source comprising, in combination, at least one indicator having a plurality of electrically energized character forming segments which become illuminated when energized, means responsive to data from the source for selectively energizing said segments to define predetermined characters, and means for generating an error signal when any of said segments fails to illuminate or extinguish in accordance with data from the source.

2. A character display, as set forth in claim 1, and including a plurality of indicators each having a like plurality of electrically energized character forming segments, and means for multiplexing data from the source to said indicators, said multiplexing means including means for sequentially enabling each indicator as data for such indicator is available from the source.

3. A character display, as set forth in claim 2, wherein each segment of each indicator is illuminated by passing a current between first and second electrodes in a gas discharge tube defining such segment, wherein said energizing means includes means connecting the first electrode for each segment on each indicator to the first electrodes of all corresponding segments of said indicators, and wherein each indicator is enabled by connecting said second electrodes for all segments on such indicator to a power source.

4. A character display, as set forth in claim 3, wherein said error signal generating means includes means responsive to an open circuit on any segment of an enabled indicator for generating an error signal.

5. A character display, as set forth in claim 1, wherein said error signal generating means includes means responsive to an open circuit in any segment of said indicator for generating an error signal.

6. A circuit for verifying the correct operation of an indicator operated from a data source, said indicator having a plurality of electrically energized character forming segments which become illuminated when energized, each segment having a first high voltage drop when open-circuited, a second voltage drop lower than such first voltage drop when illuminated, a third voltage drop lower than such second voltage drop when extinguished and a fourth voltage drop lower than such third voltage drop when short-circuited, said apparatus comprising, in combination, means responsive to data from the source for selectively energizing said indicator segments to define predetermined characters, a comParator having two corresponding groups of inputs, said comparator generating a verification signal when the two groups of inputs are identical and an error signal when the two groups of inputs are different, means for applying the data from the source to a first of said groups of comparator inputs, a plurality of electronic switch means, means connecting a different one of said switch means to each of said indicator segments for monitoring the voltage drop across said segments, each of said switch means having a first state of conducion when the voltage drop across the connected segment exceeds a predetermined voltage between said second and third voltage drops and a second state of conduction when the voltage drop across the connected segment is less than the predetermined voltage, and means connecting said switch means to the second of said groups of comparator inputs, said connecting means applying signals on said second group of comparator inputs corresponding to the signals on the first group of inputs when all of the indicator segments are illuminated and extinguished in accordance with the data from the source and applying a different input for any segment which fails to illuminate or extinguish in accordance with the data from the source.

7. A circuit for verifying the correct operation of an indicator, as set forth in claim 6, and including means for applying a predetermined signal to one input in one of said groups of comparator inputs and means for applying a similar signal to the corresponding input in the other group of comparator inputs when the voltage drop across any indicator segment is less than a second predetermined voltage between such first and second voltage drops and for applying a different signal to the corresponding input when the voltage drop across any indicator segment exceeds such second predetermined voltage whereby said comparator generates an error signal when any indicator segment is open-circuited.