Static Characteristics of Instruments
Static characteristics describe an instrument's performance under steady-state conditions, measuring accuracy, precision, sensitivity, range, linearity, hysteresis, and resolution. These parameters indicate measurement quality and help select appropriate instruments. These characteristics determine instrument suitability for specific applications and guide calibration requirements.
Key parameters:- Accuracy: Closeness to true value (% of full scale)
- Precision: Measurement repeatability
- Sensitivity: Output change per input change
- Range: Measurement limits (min to max)
- Resolution: Smallest detectable increment
- Linearity: Deviation from proportional response
- Hysteresis: Path dependence in measurements
- Dead band: Input range with no output change
- Sensor (Primary Sensing Element)
Converts physical measurand into quantifiable output signal (e.g., displacement, voltage). Interfaces directly with measured parameter and initiates signal chain.
- Signal Conditioner (Variable Conversion Element)
Transforms sensor output into standardized signal format while preserving signal integrity. Functions as intermediary transducer for signal standardization and initial processing.
- Signal Processing Unit (Variable Manipulation Element)
Performs signal conditioning operations including amplification, filtering, and linearization. Maintains signal type while optimizing signal-to-noise ratio and measurement resolution.
- Data Communication Interface (Data Transmission Element)
Enables signal routing between distributed system components via standard protocols. Critical for remote operations and distributed control architectures. Implements necessary error checking and signal integrity preservation.
- Human-Machine Interface (Data Presentation Element)
Converts processed signals into human-interpretable format through visualization tools and displays. Enables real-time monitoring, control operations, and data analysis. Implements MOX (Monitoring, Operation, eXamination) functionality for system interaction.
Choosing Appropriate Measuring Instruments
The starting point for selecting the most suitable instrument for measuring a specific quantity in a production plant or other system is the specification of the instrument characteristics required, especially parameters such as the desired measurement accuracy, resolution, sensitivity and dynamic performance.