Instruction manual

SITRANS TW
A5E00054075-05
101
Functions / Operation by HART
4.2 Parameterizable functions
4.2.1 Line break monitoring and short-circuit testing
A measuring channel-related line break monitoring can be carried out for resistance
thermometers, resistance transmitters, thermocouples and mV transmitters. Line
break testing is not possible in devices for measuring current or voltages > 1V
(device order designation 7NG3242-xxxx[1-8]). If there is a line break, no reference
temperature of the internal sensor (electronic temperature) can be determined.
A measuring channel-related short-circuit monitoring is only possible in resistance
thermometers and resistance transmitters. The threshold value for the short-circuit
test is freely parameterizable within the measuring limits.
4.2.2 Adjusting line resistances
It is possible to adjust line resistances for the following measurements:
• Resistance thermometer or resistance transmitter in two-wire circuit
• Resistance thermometer or resistance transmitter for forming difference or
average value
• Thermocouple with external reference point with Pt100 in two-wire circuit
Adjustment takes place by numeric specification of the measured line resistance
(sum of supply and return conductor) or by measuring directly with the operating
software.
4.2.3 Measuring line resistances
Depending on the interface module (see chapter 6.4, page 129) line resistances can
be measured on the measuring channel 1, measuring channel 2 or the line resist-
ance to the external resistance thermometer (as a reference point to a thermocou-
ple). To do this, the appropriate measuring channels must be short-circuited and the
line resistance measuring parameters activated.
The measured resistance values are stored in the parameters for the line
compensation.
4.2.4 Measured value offset
For application in which the process variable to be measured cannot be measured
directly at the measuring point, a measuring channel-related offset behavior can be
parameterized.
4.2.5 Scaling factor
The scaling factor serves for characteristic adaptation in series or parallel circuiting
of resistance thermometers and thermocouples. It should be multiplied by their basic