Metrix OX9302-BUS, User Manual

Page: 134 / 143

Appendix - "Bus analysis" mode
134
12.12.3. Measurements (Profibus DP)
Diagnosis
Use this table to troubleshoot problems on a measurement :
Measurement Description Diagnosis
VOffset
Offset measurement on the
RxD-P or TxD-P signal

Chassis-ground disturbance problem

Common mode problem

Cable length not compliant with standard

….
VLevel
Signal amplitude measurement ((RxD-
P/TxD-P) -(RxD-N/TxDN))

Termination problem

Junction connection (oxidation, bad contact,
etc.)

Cable length not compliant with standard

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)

…
Time Data
Measurement made using the bit time
total.

Unsuitable or damaged cable

Termination impedance incorrectly positioned

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)

…
Time Rise
Rise time between 10% and 90% of
the signal amplitude

Unsuitable or damaged cable (the rise and fall
times increase with the cable impedance)

Termination impedance incorrectly positioned

…
Time Fall
Fall time between 90% and 10% of
the signal amplitude
Jitter
Measurement made using the bit time
total

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)

…
Over+
Measurement of the positive
overshoot compared to the signal
amplitude

Unsuitable cable impedance

Termination problem (if there is no termination,
major overshoot and the opposite if the bus
impedance is too high)

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)

…
Over-
Measurement of the negative
overshoot compared to the signal
amplitude