4. Troubleshooting
Possible Cause Possible Solution
Excessive noise or ripple.
Low level signal.
Place the HPC401 Interface leads across the
resistor and check if communication is working.
Verify field-wiring shield is grounded at one end
only. Normally, the shield is grounded at the
power supply side only.
Insufficient loop resis-
tance.
Add an additional 250-ohm resistor in series to the
current loop.
Interface is not con-
nected.
Refer to the Hardware Setup & Usage section of
this manual.
Field device is not pow-
ered or polarity is re-
versed or insufficient loop
current and voltage at the
field device terminal.
Verify power supply and field device.
The Palm battery has
been discharged past the
normal range.
Recharge the Palm battery.
More than one device
using the same address.
Poll for device by TAG name rather than address.
Disconnect one device, change the connected
device address and reconnect the first device.
Field device configured in
multi-drop mode. It is
using an address other
than zero.
Execute polling address operation scanning from
address 1 to 15.
Problem
No Communication
or
Intermittent
Communication
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