Siemens Simatic S7-400 - Manual (Page 621)

Glossary
Glossary-15
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Reference channel error
Parameter in STEP 7 for analog input modules. Using this parameter, you can
enable the group error message of the reference junction when thermocouples
are used. A reference channel error occurs when thermocouples are used and
the following occurs:
• If an error occurs (for example, wire break) on a reference channel on which a
thermal resistor (RTD) is connected to compensate for temperature drift
(channel 0).
• If the
³
reference temperature is outside the permissible range of values.
Each input channel that is assigned the “RTD on Channel 0” reference junction
has a reference channel error in the situation described above. The measured
temperature is no longer compensated.
Reference potential
Potential from which the voltages of the circuits involved are viewed and
measured.
Reference temperature
Parameter in STEP 7 for analog input modules. The reference temperature is the
temperature at the reference junction (in 1/100
o C climatic temperature range)
when thermocouples are used. The reference temperature makes it possible to
measure the temperature correctly using thermocouples. The temperature at the
reference junction must be known because a thermocouple always measures the
difference in temperature between the measuring point and the reference
junction.
Repeater
A device for the amplification of bus signals and connection of ³ bus segments
over long distances.
Resolution
With analog modules, the number of bits which represent the digitized analog
value in binary. The resolution depends on the module and with analog input
modules on the
³ integration time. The precision of the resolution of a measured
value increases with the length of the integration time. The resolution can be as
many as 16 bits, including sign.
Response time
The response time is the time from an input signal being detected to the change
to an output signal linked to it.
The actual response time is somewhere between a shortest and a longest
response time. When configuring a system, you must always assume the longest
response time.