Siemens SITRANS T4200, Руководство по эксплуатации, Страница: 48 / 100

Functions
9.2 Broken wire monitoring
SITRANS TH200/TH300
Operating Instructions, 06/2010, A5E00393069-03
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9.2 Broken wire monitoring
Broken wire monitoring on a specific measurement channel can be performed for
thermocouples and millivolt transmitters. Break monitoring is permanently active in
resistance thermometers and resistance-type transmitters. No reference temperature of the
internal sensor which measures the electronics temperature can be obtained if there is a
broken wire.
When broken wire monitoring is switched on, all sensor cables are permanently monitored
for broken wires. The programmed fault current, 3.6mA to 23mA, is output in the event of an
error.
Note
If a broken wire occurs when broken wire monitoring is switched off, invalid values may be
obtained for the measured value and the internal electronics temperature in the min/max
pointer pairs and their runtime meters.
9.3 Short-circuit monitoring
Short circuit monitoring on a specific measurement channel is only possible with resistance
thermometers and resistance-type transmitters. The threshold value for the short circuit
check can be set in the parameters.
The programmed fault current, 3.6mA to 23mA, is output in the event of a sensor short
circuit.
9.4 Line compensation
Trimming the line resistance values can be performed in the following measurements:
● Resistance thermometer or resistance-type transmitter in two-wire connection
● Resistance thermometer or resistance-type transmitter for calculating differential value or
mean value
● Thermocouple with external cold junction with Pt100 in two-wire connection
The trimming is performed by numerical preset of the measured line resistance. The line
resistance is the combined total of sending and return conductors.
9.5 Type of characteristic curve (rising or falling)
The type of the characteristic curve at the 4 to 20 mA analog output can be selected (rising
or falling). The characteristic curve type is defined as follows by setting the parameters for
the start of scale value and full scale value:
● Rising characteristic: Full scale value is greater than start of scale value.
● Falling characteristic: Full scale value is less than start of scale value.