Smart transmitters are an improvement over the conventional analog transmitter. They come with microprocessors that are an integral part of the device. They are more accurate and come with their own diagnostic abilities. The smart transmitter uses the Highway Addressable Remote Transducer, which is considered the industry standard for how field devices communicate with a control system. Because they are a different device with different capabilities, how they must be calibrated is fundamentally different as well.
How Calibration Of A Smart Transmitter Works
One or more pieces of calibration equipment are needed in order to provide a reference standard. These pieces of equipment provide an input and then measure the output that results in a process that is known as digital trimming. By carrying out the digital trimming process, the digital signal produced by the transmitter can be modified in order to match the plant standard. Also, certain effects of the installation process may make it necessary to engage in digital trimming. Often, you will need to trim the digital circuit for the analog-to-digital converter input. The analog-to-digital converter output may also need to be trimmed. Which trim is performed is based on the type of transmitter that will be used.
The calibration process may involve a trimming of the high or low trim functions. Unlike with the other types of transmitters, the smart transmitter functions are considered separate and the trimming of one function does not affect the other function.
Getting The Calibration Right
Once the error has been determined, in order for the transmitter to be correctly calibrated, the error must be corrected until it is within the range specified by the manufacturer of the plant. The trim will need to keep being performed until this error is corrected. There is also an error between the mA value and the digital milliamp value. These must also be within the error specification determined by the manufacturer.
Consider Contacting Calibration Services
While you can perform a transmitter calibration yourself with the right equipment, you may find it better to contact calibration services. By doing so, you can be certain that your transmitter will be calibrated properly and you will also have a service that can test the calibration to determine if it is correct when your transmitter is not functioning properly. When the transmitter is functioning properly, it will be able to communicate with exactly whichever device it needs to communicate with.
Check with companies like Cooper Controls Inc for more information.