Technique and apparatus for measuring a direct current flowing through a conductor at high voltage

• US 5,666,048 A
• Filed: 06/26/1995
• Issued: 09/09/1997
• Est. Priority Date: 06/26/1995
• Status: Expired due to Term

• Current Assignee: Beckman Instruments, Inc. (Danaher Corporation)
• Original Assignee: Beckman Instruments, Inc. (Danaher Corporation)
• Inventors: Fassett, John R., Labriola, Donald P. II
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): KOBERT, RUSSELL MARC
• Application Number:
  US08/494,477
• Time in Patent Office: 806 Days
• Field of Search: 324/96, 324/120, 324/122, 324/133, 204/452, 204/453, 204/455, 204/602, 204/604, 204/605
• US Class Current: 324/120
• CPC Class Codes: G01N 27/44713 Particularly adapted electric power supply
• CPC Class Codes: G01R 15/22 using light-emitting devices, e.g. LED, optocouplers G01R31/31901 takes precedence

Abstract

A technique and circuit for measuring direct current flowing through a conductor at a high voltage employs a capacitor connected in series with the conductor, and a neon lamp connected in parallel with the capacitor. The series connected capacitor and conductor are connected to a high voltage source such that the current flowing through the series connected capacitor and conductor charges up the capacitor. Since the capacitor and the neon lamp are connected in parallel, the voltage across the electrodes of the neon lamp follows the voltage across the capacitor. When the voltage across the electrodes of the neon lamp reaches the lamp'"'"'s ignition voltage, the neon lamp fires, and discharges the capacitor until the voltage across the electrodes of the neon lamp falls to the lamp'"'"'s extinction voltage. The light signal generated by the neon lamp is picked up by a fiber optic cable and transmitted to a remote receiver for processing. The direct current flowing through the conductor may then be calculated by the remote receiver from the frequency of the transmitted light signal, or a qualitative indication of the current may be made through visual observation of the lamp'"'"'s intensity.

Claims

1. An apparatus for electrophoretic separation of one or more samples, comprising:

a plurality of separation channels containing said sample(s) and an electrolyte;

voltage supply having a high voltage terminal and a low voltage terminal for passing direct electrical currents through the channels to cause the sample(s) to separate into components;

a plurality of capacitors, each capacitor connected between the high voltage terminal and a corresponding separation channel so that the direct current passing through each capacitor and its corresponding separation channel will charge such capacitor;

means for causing each of the capacitors to discharge when voltage across each of the capacitors reaches a maximum voltage; and

means for determining the magnitudes of the direct currents.

2. The apparatus of claim 1, said causing means including a neon lamp.

3. The apparatus of claim 1, said determining means including a current limiting resistor.

4. The apparatus of claim 1, said causing means including a neon lamp, wherein said resistor is connected in series with the lamp.

5. The apparatus of claim 1, said determining means including means responsive to light emission from the lamp for determining frequency of discharge of the capacitor.

6. The apparatus of claim 1, further comprising an optical path for communicating the magnitude of the direct current.

7. The apparatus of claim 1, wherein said voltage supply passes direct currents of magnitude in the range of about 1 to 100 microamps to the separation channels.

8. The apparatus of claim 1, further comprising a buffer, said separation channels having two ends, wherein one end of each channel is in electrical contact with said buffer, said buffer being at a reference potential.

9. The apparatus of claim 1, said reference potential being substantially ground potential.

10. The apparatus of claim 1, said causing means including a gas discharge lamp.