Analog Process Variable Transmitter with Remote Electronic Calibration
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Solution Overview
Problem
Existing analog process variable transmitters require manual calibration of zero and span potentiometers, which poses design constraints, increases size, and exposes hazardous environments due to the need for external access, especially in explosive or submersible nuclear environments.
Innovation Solution
Implementing electrically controlled motorized actuators within the transmitter housing to adjust analog circuit components, allowing remote calibration through software and eliminating the need for external access points, thus enabling a fully enclosed and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual calibration of zero and span potentiometers is implemented through external access points, then calibration adjustability is improved, but device size increases and reliability deteriorates due to exposure of hazardous environments
Solution Approach 1:
The patent replaces manual mechanical adjustment of potentiometers with an electronic motorized actuator system. The actuator is controlled by a microprocessor that receives calibration commands through the two-wire control loop, eliminating the need for external mechanical access points and thereby preventing exposure of hazardous environments while maintaining calibration adjustability.
Solution Approach 2:
The motorized actuator serves multiple functions: it adjusts both zero and span calibration parameters, and can be controlled through the existing two-wire control loop used for normal transmitter operation. This multi-functionality eliminates the need for separate calibration access mechanisms while improving reliability.
2Ease of operation
If external access points are provided for potentiometer adjustment, then calibration ease is improved, but device complexity increases
Solution Approach 1:
The patent eliminates complex mechanical access structures by replacing them with an electronically controlled actuator system. The actuator integrates directly into the housing and is controlled through electrical signals, simplifying the overall device structure while maintaining calibration accessibility through the control loop.
3Reliability
If motorized actuators are used for electronic calibration, then device size is reduced and reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces complex mechanical calibration mechanisms with an electronically controlled actuator system. The actuator, driven by a microprocessor through the existing two-wire control loop, provides precise calibration control with fewer mechanical parts, improving reliability while the modular design facilitates manufacturing.
4Reliability
If rotary adjustment shafts with flame paths are used, then hazardous environment sealing is improved, but calibration precision deteriorates due to mechanical hysteresis
Solution Approach 1:
The patent replaces mechanical rotary adjustment shafts with a motorized actuator controlled by a microprocessor. This eliminates mechanical hysteresis and play in the adjustment mechanism, providing precise span and zero setting while maintaining flame path sealing through the intact housing structure.
Solution Approach 2:
The microprocessor-controlled actuator system incorporates feedback control to achieve precise calibration settings. The system can detect the actual potentiometer position and make fine adjustments accordingly, eliminating the precision errors inherent in mechanical hysteresis of rotary shafts.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution facilitates precise and repeatable calibration without exposing hazardous environments, reduces transmitter size, and enhances reliability and robustness against vibration and seismic activity.
Implementation Method 1
A motorized actuator is configured to adjust the adjustable analog circuit component
Data Source
AI summary
A process variable transmitter for measuring a process variable includes a process variable sensor configured to sense a process variable and provide a sensor output. Measurement circuitry receives the sensor output and provides a measured output related to the process variable. Output circuitry provides a device output on a two-wire process control loop based upon the measured output. The output circuitry has a transfer function that is a function of an adjustable analog circuit component. A motorized actuator is configured to adjust the adjustable analog circuit component to thereby change the transfer function of the output circuitry. An optional calibration controller is also provided.