Level sensor and washer unit

• US 6,212,949 B1
• Filed: 09/01/1998
• Issued: 04/10/2001
• Est. Priority Date: 10/27/1995
• Status: Expired due to Fees

• Current Assignee: Dynex Technologies, Inc.
• Original Assignee: Dynex Technologies, Inc.
• Inventors: Inder, David John, Higgs, Paul Anthony, Le Feuvre, Peter John
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): CYGAN, MICHAEL T
• Application Number:
  US09/065,074
• Time in Patent Office: 952 Days
• Field of Search: 733/04.R, 732/90.R, 732/91, 732/98, 738/630.1, 738/637.1, 738/640.1, 738/641.1, 738/665, 422/63, 422/67, 422/82.02, 422/100, 422/106, 338/38, 340/620, 340/648
• US Class Current: 73/304.00R
• CPC Class Codes: B01L 13/02 for receptacle or instruments
• CPC Class Codes: B01L 3/5082 Test tubes per se
• CPC Class Codes: G01F 23/245 with a probe moved by an auxiliary power, e.g. meter, to follow automatically the level
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors
• CPC Class Codes: G01N 2035/1025 Fluid level sensing
• CPC Class Codes: G01N 35/1065 Multiple transfer devices

Abstract

A fluid level sensor and a washer unit are provided for an automated immonoassay processing system. A washer head (13) is vertically movable by a drive (2) above a reaction tray (8) having fluid (15) in separate cells. The level sensor comprises two electrodes arranged along a fluid path within aspirator tips (6). The electrodes are held at different electrical potentials and are effectively insulated from each other. If fluid is aspirated along the fluid path then the electrodes are bridged. Control means (1) is arranged to detect any change in conductance between the electrodes thereby indicating the presence of fluid (15). The vertical height of the washer head is determined relative to the sample thereby enabling the device to determine the level of the fluid (15).

Claims

1. An automated immunoassay processing system including a level sensor, comprising:

a head mounted for vertical movement, said head comprising an aspirate tip having an internal flow passage within and along which first and second electrode means are provided, each forming a part of the flow passage and being connected to a detector circuit arranged to give an output signal when the electrode means are bridged by fluid;

aspirating means connected to the aspirate tip;

a motor for moving the head;

a positioning circuit for controlling the motor to position the head at specified vertical positions; and

control means connected to receive the output signal of the detector circuit;

characterized in that;

the aspirating means is arranged to aspirate while the head is being lowered towards the surface of the fluid;

the first and second electrode means are insulated from each other and vertically positioned so that in use fluid passes through said first electrode means before passing through said second electrode means; and

the control means is arranged to produce an indication of the level or volume of fluid in a reaction cell by reference to a vertical position signal when the detector circuit gives an output signal on the aspirate tip coming into contract with fluid in the reaction cell and to generate an output indicating the presence of fluid passing between said first and second electrode means while the fluid is being aspirated from the reaction cell.

2. An automated immunoassay processing system as claimed in claim 1, wherein the control means comprises a processor arranged to produce vertical position signals for controlling the motor in accordance with a stored program.

3. An automated immunoassay processing system as claimed in claim 1, wherein the electrode means comprise two axially spaced metal tubes.

4. An automated immunoassay processing system as claimed in claim 3, wherein the metal tubes are mounted in an insulating block having a through passage which has a narrower-diameter axially-central portion providing two shoulders against which the tubes abut.

5. An automated immunoassay processing system as claimed in claim 1, wherein the head further comprises a dispensing tip for dispensing washing fluid into a reaction cell.

6. An automated immunoassay processing system including a level sensor, comprising:

a head mounted for vertical movement, said head comprising an aspirate tip having an internal flow passage within and along which first and second electrode means are provided, the electrode means being connected to a detector circuit arranged to give an output signal when the electrode means are bridged by fluid;

aspirating means circuit for controlling the motor to position the head at specified vertical positions; and

control means connected to receive the output signal of the detector circuit;

characterized in that;

the aspirating means is arranged to aspirate while the head is being lowered towards the surface of the fluid;

the first and second electrode means are sequentially positioned so that in use fluid passes through said first electrode means before passing through said second electrode means; and

the control means is arranged to produce an indication of the level or volume of fluid in a reaction cell by reference to a vertical position signal when the detector circuit gives an output signal on the aspirate tip coming into contract with fluid in the reaction cell and to generate an output indicating the presence of fluid passing between said first and second electrode means while the fluid is being aspirated from the reaction cell, said head further comprising a;

dispensing tip arranged to dispense washing fluid into a reaction cell with both the dispensing and aspirate tips positioned above the cell, and wherein after the washing fluid is dispensed the aspirate tip is lowered while aspirating, the control means being arranged to produce an indication of the level of washing fluid when the aspirate tip reaches the fluid surface, whereby the dispensing of a correct quantity of washing fluid may be confirmed.

7. An automated immunoassay processing system as claimed in claim 6, wherein the aspirate tip is arranged to be positioned within the reaction cell and to aspirate while washing fluid is being dispensed from the dispense tip, the control means being arranged to time the period between commencement of dispensing and detection of fluid by the detector circuit when the fluid level reaches the aspirate tip, to confirm that the fluid is being dispensed at an acceptable rate.

8. An automated immunoassay processing system as claimed in claim 6, wherein before a wash cycle, the head is lowered while aspirating and the control means produces an indication of the level of a reagent previously dispensed, so that samples having insufficient reagent can be rejected.

9. A method of sensing a level of fluid in a reaction cell of an automated immunoassay processing system comprising a head, first and second electrode means said electrode means being vertically spaced apart, and an aspirate tip comprising the steps of:

lowering the head towards the reactions cell while generating a vertical position signal of said head relative to said cell;

aspirating while lowering the head;

outputting a signal from each of said electrode means when the first and second electrode means are bridged by fluid passing through said electrode means and aspirate tip;

producing an indication of the level of fluid in the reaction cell by reference to a vertical position signal when the aspirate tip comes into contract with fluid in the reaction cell; and

generating an output indicating presence of fluid passing between the first and second electrode means while the fluid is being aspirated from the reaction cell.