Method for compensating errors in a pressure transducer

• US 5,269,311 A
• Filed: 05/11/1992
• Issued: 12/14/1993
• Est. Priority Date: 08/29/1989
• Status: Expired due to Term

• Current Assignee: Hospira Incorporated (Pfizer Inc.)
• Original Assignee: Abbott Laboratories
• Inventors: Kirchner, Richard A., Shotter, Timothy A., Beard, deceased, Robert W.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): ZELE, KRISTA MICHELLE
• Application Number:
  US07/881,726
• Time in Patent Office: 582 Days
• Field of Search: 128/672, 128/673, 128/675, 128/748, 73/1 R, 73/4 R, 73/708, 73/766, 73/765, 338/3, 338/4, 604/65, 604/67, 364/571.02, 364/571.03
• US Class Current: 600/485
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: G01L 1/2281 for temperature variations
• CPC Class Codes: G01L 27/002 Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination

Abstract

Disclosed is a method of compensating any of a plurality of different pressure transducers for their characteristic pressure sensitivity, zero pressure offset, and self-heating error. The method comprises selecting a gain resistor that adjusts the gain of an output signal of the pressure transducer in use so that the pressure transducer appears as an ideal pressure transducer to a pressure monitor. The self-heating error is compensated by measuring an initial bridge voltage that drives the transducer and an initial output signal of the pressure transducer when the transducer is first energized. After a period of time a second bridge voltage and a second output signal are determined. The self-heating error is determined as a function of the difference between the initial and second values. The zero pressure offset is compensated by determining the output signal of the pressure transducer at zero gauge pressure after the pressure has been compensated for the self-heating error.

Claims

1. A method for using a pressure transducer to monitor pressure and for compensating for variances in both a characteristic pressure sensitivity and a zero pressure offset of an output signal of the pressure transducer, comprising the steps of:

(a) providing a gain resistor that is unique to the pressure transducer, wherein the gain resistor has a resistance that compensates for the characteristic sensitivity of the pressure transducer such that when the pressure transducer is used to monitor pressure, the output signal varies with pressure in a predetermined manner;

(b) determining a zero pressure offset compensation to compensate for the zero pressure offset of the pressure transducer; and

(c) compensating the output signal from the pressure transducer for the zero pressure offset while monitoring the pressure with the pressure transducer.

2. The method of claim 1, further comprising the steps of determining a self-heating error and an ambient temperature correction for the pressure transducer before the step of monitoring the pressure;

and, while the pressure transducer is used to monitor the pressure, compensating the output signal from the pressure transducer for the self-heating error and the ambient temperature correction.

3. The method of claim 2, further comprising the step of using a microprocessor to determine the zero pressure offset, the self-heating error, and the ambient temperature correction, said microprocessor being disposed in a reusable cable intended for use with each of a plurality of disposable pressure transducers, and associating an electrical cable including the gain resistor with each disposable pressure transducer.

4. The method of claim 2, wherein the step of determining a self-heating error and an ambient temperature correction for the pressure transducer comprises the steps of:

determining initial values of the output signal and an excitation voltage for the pressure transducer when first energized;

waiting a predetermined interval of time and determining second values of the output signal and excitation voltage for the pressure transducer;

determining a difference between the initial and second values; and

determining the self-heating error and the ambient temperature correction as a function of the difference between the initial and second values.

5. The method of claim 1, wherein the step of compensating the output signal from the pressure transducer for the zero pressure offset comprises the step of providing a zero pressure offset resistor having a resistance selected to compensate the zero pressure offset, said zero pressure offset resistor being integral with an electrical cable that conducts electrical signals to and from the pressure transducer.

6. The method of claim 1, further comprising a step of coupling the pressure transducer through an electrical cable to an input of a pressure monitor, wherein said electrical cable includes a compensation circuit that performs the steps of compensating for the zero pressure offset when the pressure transducer is used to monitor pressure, the compensation circuit having an output impedance and the input of the pressure monitor having an input impedance, the method further comprising the step of matching the output impedance of the compensation circuit with the input impedance of the input of the pressure monitor.

7. The method of claim 6, wherein the pressure monitor supplies an excitation current to the pressure transducer through the electrical cable, the method further comprising the step of powering said compensation circuit from the excitation current supplied by the pressure monitor.