SMAR FY301, Instruction, Operations & Maintenance Manual

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FY301 - Operation, Maintenance and Instructions Manual
2.2
Electronics Functional Description
Refer to the block diagram (Figure 2.2). The function of each block is described below.
A/D
Receives the 4 - 20 mA signal and converts it in the digital format for the CPU.
D/A
Receives the signal from the CPU and converts it to an analog voltage proportional to the desired
position, used by the control.
Control
Controls the valve position according to data received from the CPU and the Hall effect sensor
feedback.
Position Sensor
Measures the actual position and feedback to the control and CPU.
Temperature Sensor
Measures the temperature of the Transducer Circuit.
Isolation
Isolates the 4 - 20 mA signal from the piezoelectric signal.
EEPROM
A non-volatile memory that stores configuration data as a backup if the FY301 main board be replaced.
Central Processing Unit (CPU), RAM, PROM and EEPROM
The CPU is the intelligent portion of the positioner, being responsible for the management and
operation of block execution, self-diagnostics and communication. The program is stored in PROM. For
temporary storage of data there is a RAM. The data in the RAM is lost if the power is switched off,
however the device also has a nonvolatile EEPROM where data that must be retained is stored.
Examples of such data are calibration and valve configuration.
HART Modem
The function of this system is to make possible the information exchange between Smar programmer
and the positioner, over digital communication using Hart
®
protocol. Modulates and demodulates digital
information transmitted by Smar programmer on the current line. A “1” is represented by 1200 Hz and
“0” by 2200 Hz. The frequency signal is symmetrical and does not affect the DC-level of the 4 - 20 mA
signal.
Power Supply
The positioner circuit receives supply from a 4 - 20 mA power supply or takes power of Loop Line to
power the positioner circuit that is limited to 3.8 mA to work properly.
Display Controller
Receives data from the CPU and controls the (LCD) Liquid Crystal Display.
Local Adjustment
Local adjustment is provided by means of two magnetically actuated switches with no external electric
or mechanical contact, by using a magnetic screwdriver.
Piezo Flapper Nozzle
The unit flapper nozzle converts the movement of piezoelectric into a pneumatic signal to control
pressure in the pilot chamber.
Restriction
The restriction and the nozzle form a pressure-divided circuit. Air is supplied to the nozzle through a
restriction.
Spool
The spool ensures a quick valve positioning by providing a greater airflow than one provided by the
restriction.