SMAR TT400WH, Руководство пользователя

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Section 2
2.1
OPERATION
The TT400 Wireless HART TM accepts signals from mV generators such as thermocouples or resistive
sensors such as RTDs. The criterium is that the signal is within the range of the input. For mV, the
range is -50 to 500 mV and for resistance, 0 to 2000 Ohm.
Functional Description-Hardware
Refer to the block diagram (Figure 2.1). The function of each block is described below.
INPUT BOARD
SIGNAL
CONDITIONER
AD
CONDITIONER
RTD
TC
OHM
mV
AMBIENT
TEMPERATURE
SENSOR
MAIN BOARD
PROCESSING UNIT
HART MODEM
Burst Mode
SPECIAL FUNCTIONS
WirelessHART Protocol
LCD
CONTROLLER
Local
Adjustment
RF
Module
Maintenance Port
Baterry
Pack
DIGITAL
DISPLAY
Figure 2.1 – TT400 WirelessHART TM Block Diagram
Input Signal Conditioner
A function to apply
the correct gain to the input signals to make them suit the A/D converter.
A/D Converter
The A/D converts the input signal to a digital format for the CPU.
Processing Central Unit (CPU), RAM, FLASH and FRAM
The central processing unit (CPU) is the intelligent part of the transmitter responsible for the
management and operation of measurement, execution block, self-test and communication.
The program is stored in FLASH memory. For temporary storage of data, the CPU has an internal RAM.
If the power is turned off, data stored in RAM is lost.
For data storage that requires persistence, such as configuration data, calibration and identification, a
non-volatile memory type FRAM for TT400 Wireless HART TM is used. It has an access time consistent
with the RAMs normal and there is no limitation in terms of write cycles.
Modem
The function of this system is to make possible the exchange of information between the configurator
and the transmitter, through digital communications Master-Slave type.
Therefore, the transmitter makes the demodulation of the received signal serially configurator, for the
current line, and after treating it appropriately modulates the response to be sent. The HART ®
technology uses FSK for modulation of the signal.