TT301 – Operation and Maintenance Instruction Manual
2.2
depends on the voltage from the D/A converter.
Modem
Modulates a communication signal on the current line. A "1" is represented by 1200 Hz and a "0", by
2200 Hz. These signals are symmetric and do not affect the DC level of the 4-20 mA signal.
Power Supply
Power shall be supplied to the transmitter circuit using the signal line (2-wire system). The transmitter
quiescent consumption is 3.6 mA; during the operation, consumption may be as high as 21 mA,
depending on the measurement and sensor status.
The TT301, in the transmitter mode, shows failure indication at 3.6 mA if configured for low signal
failure; at 21 mA, if configured for high signal failure; 3.8 mA in the case of low saturation; 20.5 mA in
the case of high saturation and measurements proportional to the applied temperature in the range
between 3.8 mA and 20,5 mA. 4 mA corresponds to 0% of the working range and 20 mA to100 % of
the working range.
Power Isolation
Its function is to isolate power supply between the input and the CPU.
Display Controller
Receives data from the CPU informing which segments of the Liquid Crystal Display, should be turned
on.
Local Adjustment
Two switches that are magnetically activated. They can be activated by the magnetic tool without
mechanical or electrical contact.
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