112
MODEL 5081-A
SECTION 15.0
TROUBLESHOOTING
15.9 SIMULATING INPUT CURRENTS - DISSOLvED OxyGEN
to check the performance of the transmitter, use a decade box to simulate the current from the oxygen sensor.
A. disconnect the anode and cathode leads from terminals 13 & 14 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, go to the
main display and press dIAG. then press NEXt.
SEnSor
Cur
will appear in the display. Press ENtER. the display will
show the sensor current. Note the units:
µA
is microamps:
nA
is nanoamps.
d. Change the decade box resistance and verify that the correct
current is shown. Calculate the current from the equation:
current (µA) =
15.10 SIMULATING INPUT CURRENTS - CHLORINE AND OzONE
to check the performance of the transmitter, use a decade box and a battery to simulate the current from the sensor. the
battery, which opposes the polarizing voltage, is necessary to ensure that the sensor current has the correct sign.
A. disconnect the anode and cathode leads from terminals 13 & 14 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. It should be close to the value in the table. the actual value depends on the voltage of the
battery. to view the sensor current, go to the main display and press dIAG. then, press NEXt. SEnSor Cur will appear
in the display. Press ENtER. the display will show the sensor current. Note the units: uA is microamps: nA is
nanoamps.
d. Change the decade box resistance and verify that the correct cur-
rent is shown. Calculate the current from the equation:
current (µA) =
the voltage of a fresh 1.5 volt battery is about 1.6 volt (1600 mV).
Sensor
Polarizing voltage
Resistance
Expected Current
499Ado
-675 mV
34 k
W
20 µA
499Atrdo
-800 mV
20 k
W
40 µA
Hx438 and Gx448
-675 mV
8.4 M
W
80 nA
Sensor
Polarizing voltage
Resistance
Expected Current
499ACL-01 (free chlorine)
200 mV
28 M
W
500 nA
499ACL-02 (total chlorine)
250 mV
675 k
W
2000 nA
499AoZ
200 mV
2.7 M
W
500 nA
FIGURE 15-1. Simulate dissolved oxygen.
FIGURE 15-2. Simulate chlorine and ozone.
V
battery
– V
polarizing
(mV)
resistance (k
W
)
voltage (mV)
resistance (k
W
)
