Analogue voltage indicator with sequence of light emitting diodes

• US 4,243,985 A
• Filed: 05/04/1978
• Issued: 01/06/1981
• Est. Priority Date: 05/04/1978
• Status: Expired due to Term

• Current Assignee: Chronolog Systems Limited
• Original Assignee: Chronolog Systems Limited
• Inventors: Quayle, Ian H.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/902,663
• Time in Patent Office: 978 Days
• Field of Search: 324/96, 324/122, 340/753, 340/754, 340/782, 340/811, 340/813
• US Class Current: 345/39
• CPC Class Codes: G01R 13/405 using a plurality of active, i.e. light emitting, e.g. electro-luminescent elements, i.e. bar graphs

Abstract

A circuit serves to illuminate appropriate light emitting diodes of a sequence to provide a bar graph type display of an analogue input voltage. The light emitting diodes are divided into sets with each set being associated with a respective signal processing element which may be a differential amplifier supplied with the analogue input voltage at one input terminal and a unique off-set voltage at the other. The signal processing elements handle respective contiguous ranges of the analogue voltage and the required supply voltage is reduced.

Claims

1. Analogue voltage display means comprising:

an analogue voltage input for receipt of an analogue voltage signal to be displayed;

a plurality of sets of light emitting diodes, said sets being together arranged to provide a display of a single sequence of light emitting diodes;

a plurality of signal offsetting elements, there being one such element for each set of light emitting diodes, each signal offsetting element being connected with said input to receive the analogue voltage signal;

offset voltage means supplying a different offset voltage to each signal offsetting element whereby the elements provide, over respective contiguous ranges of the analogue voltage signal, respective offset analogue voltage signals which are indicative of the analogue voltage signal to be displayed and which vary within voltage ranges which are similar as between the signal offsetting elements; and

a plurality of control means, there being one such control means for each set of light emitting diodes, each control means being connected to receive the offset voltage signal from the corresponding signal offsetting element and comprising reference means which defines levels of the said offset voltage signal corresponding respectively with the light emitting diodes of the associated set and a semiconductor switch for each light emitting diode of the associated set, each semiconductor switch being actuable selectively to enable or inhibit current flow through the light emitting diode, the semiconductor switches for each set being respectively actuated as the corresponding offset analogue voltage signal reaches the levels defined for the respective light emitting diodes of the set, so that the light emitting diodes of the sequence are illuminated at unique levels of the analogue voltage signal to provide a visual indication thereof.

2. Electrical circuit means according to claim 1, wherein the signal offsetting elements comprise respective differential amplifiers having first input terminals connected to said input and second input terminals connected for receipt of the associated off-set voltage.

3. Electrical circuit means according to claim 2, wherein said first input terminals are connected to the input by means of a voltage divider incorporating a thermister to compensate for the temperature coefficient of the off-set voltage means and reference means.

4. Electrical circuit means according to claim 3, wherein said voltage divider further incorporates a potentiometer for calibration.

5. Electrical circuit means according to any one of claims 2, 3 and 4, wherein the off-set voltage means comprises an off-set voltage divider and means for applying in use a fixed off-set voltage to said divider, the second input terminals of the differential amplifiers being connected to respective points of the off-set voltage divider so as to receive multiples of said off-set voltage.

6. Electrical circuit means according to claim 5, wherein the means for applying the off-set voltage comprise a junction transistor so connected as in use to provide to the off-set voltage divider an off-set voltage corresponding to the amplified base-emitter voltage of the transistor.

7. Electrical circuit means according to claim 1, wherein the semiconductor switches comprise respective junction transistors having collector and emitter connected in series with the corresponding light emitting diode between voltage rails.

8. Electrical circuit means according to claim 7 wherein the reference means for each control means comprises a chain of diodes connected at one end to the output of the associated signal processing element, the transistor bases being connected with respective points in the diode chain.