Method of operating and amperometric measuring cell

• US 5,611,908 A
• Filed: 12/21/1995
• Issued: 03/18/1997
• Est. Priority Date: 12/22/1994
• Status: Expired due to Fees

• Current Assignee: Dragerwerk AG
• Original Assignee: Dragerwerk AG
• Inventors: Matthiessen, Hans, Studer, Matthias
• Primary Examiner(s): Bell, Bruce F.
• Application Number:
  US08/576,456
• Time in Patent Office: 453 Days
• Field of Search: 205/775, 205/782.5, 205/793, 204/415, 204/431, 204/432
• US Class Current: 205/775
• CPC Class Codes: G01N 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence
• CPC Class Codes: G01N 27/49 Systems involving the determination of the current at a single specific value, or small range of values, of applied voltage for producing selective measurement of one or more particular ionic species

Abstract

The invention relates to a method for operating an amperometric measuring cell which includes at least a measuring electrode 2 and a counter electrode 3 in an electrolyte chamber 4 filled with an electrolyte. The measuring cell is closed off by a permeable membrane 7 with respect to the measurement sample to be detected. The method of the invention improves the run-in performance of the measuring cell 1. The method includes the step of applying a voltage U₁ across the electrodes (2, 3) during a first time span T₁ starting at a reference time T₀. A reference voltage U₀ is assumed at the start of the measurement and the voltage U₁ is increased relative to the reference voltage U₀.

Claims

1. A method of operating an amperometric measuring cell for measuring a sample, the measuring cell including:

an electrolyte chamber having an opening directed toward the sample to be measured and holding an electrolyte;

a permeable membrane mounted on said chamber for closing off said chamber; and

, a measuring electrode and a counter electrode disposed in said chamber so as to be in spaced relationship to each other; and

, the method comprising the steps of;

providing a voltage source outputting a voltage U for applying said voltage U across said electrodes to generate a sensor current i(t) between said electrodes; and

,

starting with said voltage U across said electrodes at a reference voltage U₀ at a reference time T_O and applying a voltage U₁ during a first time span T₁ measured from said reference time T_O with said voltage U₁ being increased relative to said reference voltage U₀, wherein the sensor current i(t) adjusts more rapidly to a sensor rest current i₀ to shorten the run time of the cell.

2. The method of claim 1, further comprising the step of applying a second voltage U₂ across said electrodes during a second time span T₂ directly after said first time span T₁ with said second voltage U₂ being dropped relative to said reference voltage U₀ ;

and, selecting said first and second time spans (T₁, T₂) so that said second time span T₂ is not greater than said first time span T₁.

3. The method of claim 2, wherein said voltages (U₁ and U₂) and said time spans (T₁ and T₂) are so selected that the product of the difference (U₁ -U₀) and T₁ divided by the product of the difference (U₂ -U₀) and T₂ is equal to or greater than 5 as follows:

##EQU3## .