GDS-68XP Operation & Maintenance Manual, Revision 3.4
Page 51
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If 4-20mA output is off-scale low or high and cannot be adjusted using DIAGNOSTICS mode,
IO/Power Supply board may be defective and should be replaced.
CONTROLLER MODBUS DATA INCORRECT
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Verify that MODBUS master is requesting data from correct data register (31002).
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Verify that controller MIN and MAX count settings are correct. MIN counts should be “800”
which corresponds to 4mA and MAX counts should be “4000” which corresponds to 20 mA.
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Verify that the GDS-68XP MODBUS address matches the address programmed into the
controller’s channel configuration.
CONTROLLER SHOWING MODBUS COMM ERROR
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Check for incorrect MODBUS polarity (swap “A” and “B” if unsure; no damage will occur).
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Verify that MODBUS master is requesting data from correct MODBUS address.
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Verify that MODBUS master is requesting data from register 31002.
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Verify that there are no other MODBUS slave devices with identical MODBUS address.
GDS-68XP DISPLAY BLANK
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Verify DC power at IO/Power Supply board, TB2, terminals 1 (+24) and 4 (Gnd).
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Verify ribbon cable connected between IO/Power Supply board and Display Assembly.