II - DCE FEL ČVUT v Praze

Special feature of
resistant
measurement
Non-connected
input channels
Adjustable types
of measurement
Adjustable
measuring ranges
Wire break check
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04
Only one channel per channel group is required for resistance measurement.
The ”2nd” channel of the group is used for current injection (IC).
The measured value is obtained on accessing the ”1st” channel of the group.
The ”2nd” channel of the group is preset with the overflow value ”7FFFH”.
During diagnostics, the 1st channel provides the actual status (in compliance
with parameterization) and the 2nd channel ”faultless”.
Activated and non-connected channels of the analog input module SM 331;
AI 8 x TC/4 x RTD must be short-circuited to ensure optimum interference
immunity for the analog input module. The non-connected channels should
also be deactivated in STEP 7 (see Section 3.6.3) in order to shorten the
module cycle time.
The following types of measurement can be set on the analog input module
SM 331; AI 8 x TC/4 x RTD. The measurement mode is set in STEP 7 (see
Section 3.6.3).
Voltage measurement
Resistance measurement
Temperature measurement
The measuring ranges, for which you can use the analog input module
SM 331; AI 8 x TC/4 x RTD are specified in the Tables 3-32 to 3-34. You can
set the required measuring ranges in STEP 7 (see Section 3.6.3).
The analog input module SM 331; AI 8 x TC/4 x RTD carries out an wire
break check, provided it is enabled by means of parameterization, for all
areas. All 4 terminal wires are monitored for wire break in resistance
thermometer mode (RTD).
Measuring ranges Table 3-32 contains all measuring ranges for voltage measurements.
for voltage
measurement
Table 3-32 Measuring ranges for voltage measurement
Selected measurement
mode
Voltage The digitized analog values are specified in Section
3.1.2 in Table 3-3 Voltage measuring ranges
SIMATIC S7 Ex Analog Modules
Explanation Measuring range
25 mV
50 mV
80 mV
250 mV
500 mV
1 V
3-57