Calibration in Fieldbus terminology

The terminology differs between the calibration of the conventional instrument and the digital one. Traditionally in metrology, the word calibration means that the instrument under test is compared to a more precise instrument and may include trimming or adjusting the instrument to show the correct readings again. In fieldbus terminology, the word calibration means that the instrument is being configured or verified.The main reason to calibrate is that even the best instruments drift and lose their ability to give precise measurements.Drift makes calibration necessary. Environment conditions, elapsed time and type of application can affect the stability of a instrument. Even instruments from the same manufacturer,type and range can show varying performance. You can find that a unit has good stability, while another performs differently.

 

Difference between conventional & fieldbus transmitters

 

Conventional transmitters

• Analog one-way signal

• Only one variable

• A pair of cable to each instrument

• Conversion of mA signal to digital for I/O subsystem

 

Field-bus transmitters

• Digital two-way signal

• Huge amount of information is transferred

• Several instrument in one bus cable(multi-drop)

• No conventional I/O systems needed

• Open standard – Instruments from any manufacturer can be in the same Field-bus

 

The main difference between a Fieldbus transmitter and conventional transmitters is that the output signal is a fully digital Fieldbus signal. Change the output signal does not change the need for periodic calibration

 

Procedure for calibrating Fieldbus transmitters

Beamex MC5 Fieldbus Calibrator,is a combination of a multifunction process calibrator and a Field-bus configurator, which can be used with both industrial standards Foundation Field-bus H1 and Profi-bus PA. It also houses HART

configuration and calibration facility

 

1. 2 persons needed for calibration

2. Make connections

3. Calibrate and document automatically – Simulate or generate the input and read the digital output of the Field-bus instrument

 

4. Trim (adjust) if required and perform As Left calibration automatically or manually

5. Upload calibration results to calibration software and print the calibration certificate

 

Advantages of using  Beamex MC5 Fieldbus

• Multifunction Calibrator + Field-bus communicator

• Single tool to be carried to the field

• Easy to use and reduces time used for calibration

• Automatic documentation of results

• Improving the processes and profitability

 

 

Artical from: https://automationforum.co/