08-02-2013, 12:27 PM
Maintenance and Calibration of HART Field Instrumentation
1Maintenance and Calibration.pptx (Size: 479.91 KB / Downloads: 78)
INTRODUCTION
Most new field instruments are now smart digital instruments. Smart is process jargon that describes any
microprocessor-based field device.
One popular digital protocol is the HART (Highway Automated Remote Transducer) protocol, which shares characteristics of both analog and digital control systems.
To properly service these instruments, precision both analog source / measure capability and digital communication are both required.
Historically, this operation has required two separate tools, a calibrator and a communicator.
Today, these capabilities are available in a single HART Documenting Process Calibrator that can help technicians quickly and effectively service a HART instrument workload.
Why HART ?
Completes required calibrations as quickly and efficiently as possible.
Instrument maintenance is moving to the field.
Reduces process interruption and avoids the time and expense of removing the instrument to the shop.
Combines calibration capabilities and essential HART communication functions in one compact, easy-to-use tool.
HART
· Is supported by all of the major vendors of process field instruments
· Preserves present control strategies by allowing traditional 4-20 mA signals to co-exist with digital communication on existing two-wire loops
· Is compatible with traditional analog devices
· Provides important information for installation and maintenance, such as Tag-IDs, measured values, range and span data, product information and diagnostics
· Can support cabling savings through use of multidrop networks
· Reduces operation costs, through improved management and utilization of smart instrument networks
What is the HART protocol?
The HART protocol uses 1200 baud Frequency Shift Keying (FSK) based on the Bell 202 standard 1 to superimpose digital information on the conventional 4-20 mA analog signal.
The HART protocol is an industry standard developed to define the communications protocol between intelligent field devices and a control system.