Instruction manual

98
MODEL Xmt-A-FF/FI SECTION 15.0
TROUBLESHOOTING
15.10 TROUBLESHOOTING NOT RELATED TO MEASUREMENT PROBLEMS
Problem Action
Display too light or too dark Change contrast (see Section 7.8.3)
“Enter Security Code” shown in display Transmitter has password protection
(see Sections 5.3 and 7.5)
15.11 SIMULATING INPUTS - DISSOLVED OXYGEN
To check the performance of the controller, use a decade box to simulate the current from the oxygen sensor.
A. Disconnect the anode and cathode leads from terminals 11 and 12 on TB1 and connect a decade box as
shown in Figure 15-1. It is not necessary to disconnect the RTD leads.
B. Set the decade box to the resistance shown in the table.
C. Note the sensor current. To view the sensor current from the
main display, press

until the Input Current screen
appears. Note the units: μA is microamps, nA is nanoamps.
D. Change the decade box resistance and verify that the cor-
rect current is shown. Calculate current from the equation:
current (μA) =
Sensor Polarizing Voltage Resistance Expected current
499ADO -675 mV 34 kΩ 20 μA
499A TrDO -800 mV 20 kΩ 40 μA
Hx438 and Gx448 -675 mV 8.4 MΩ 80 nA
voltage (mV)
resistance (kΩ)
FIGURE 15-1. Simulate Dissolved Oxygen