Troubleshooting - Siemens SIMATIC S7-300 Manual

Length measurement
The present actual position is captured at both the rising and the subsequent
falling edge of the touch probe. In addition, the actually traveled distance
(amount) is calculated.
Length measurement On
Measurement input
Process interrupt
Measurement taking place
"Measured length value"
S1 – start of length measurement
S2 – end of length measurement
∆S – Measured length value
∆t – minimum signal length at the digital input:
The following response takes place with functions that change the current
actual value:
Note
The zero offset function does not change the actual position of the axis, and
is thus not relevant for the above observations regarding the Length Measure-
ment function.
Error messages The following table lists the errors that can occur in the execution of the
Measurement function.
Error
Travel errors The "Digital input not parameterized" error is signaled when a measurement function is selected
without a digital input having been parameterized (see Troubleshooting, Table 11-7, Class 3 No. 30).
Operator The "Measurement function undefined" error is signaled when both measuring functions are selected
control errors (see Troubleshooting, Table 11-6, Class 2 No. 16).
Measuring An erroneous length measurement is indicated by signaling back the length "–1." Possible causes
error include:
Resynchronization in the Reference-Point Approach mode while a measurement is in progress
Execution of the Set Reference Point function while a measurement is in progress
Direction of travel at the falling edge is opposite to the direction of travel of the previous rising
edge
FM 354 Servo Drive Positioning Module
Resynchronization in Reference-Point Approach mode:measured length
contains measurement-error message
Set Reference Point:measured length contains measurement-error mes-
sage
Retrigger Reference Point:measured length is difference between edge
positions
Set Actual Value:measured length is actual traversed distance
Significance
Description of Functions
∆S
∆t
S1 S2
2 FM cycle
9-51