Low battery voltage indicator for a portable digital electronic instrument

• US 4,010,456 A
• Filed: 03/10/1975
• Issued: 03/01/1977
• Est. Priority Date: 03/10/1975
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Erni, Ernst R.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/556,753
• Time in Patent Office: 722 Days
• Field of Search: 340/248 B, 340/249, 340/324 R, 340/324 M, 340/336, 340/253 B
• US Class Current: 340/636.15
• CPC Class Codes: G06F 3/1407 General aspects irrespective of display type, e.g. determination of decimal point position, display with fixed or driving decimal point, suppression of non-significant zeros
• 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

Abstract

The output voltage of a battery in a portable digital electronic instrument is compared with an internal voltage reference. When the battery voltage falls below the reference voltage, the true decimal point of the number being displayed is not illuminated and a plurality of the adjacent decimal points are illuminated.

Claims

1. A digital electronic instrument comprising:

a battery;

digital circuit means responsive to an input stimulus, said digital circuit means having a digital output;

a digital display including a plurality of display modules responsive to the output of the digital circuit means, each display module having a plurality of light emitting segments for selectively displaying numerals and a decimal point, said decimal point being normally displayed in combination with a numeral on the same display module of the digital display;

a reference voltage supply; and

a comparator having a first input connected to the reference voltage supply, a second input connected to the battery, and an output for giving an output signal when the battery voltage is below the reference voltage, the output being connected to the digital display circuit means for causing the true decimal point to be extinguished and a plurality of the adjacent decimal points to be illuminated in response to an output signal from the comparator.