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DOTX-45 Dissolved Oxygen System Part 10– Troubleshooting

DOTX-45 60 -

2. If analyzer does not appear to power up (no display), remove

power and check removable fuse for continuity with a DVM.

3. Using a DVM, check the voltage across the BLUE and WHITE

wires coming from the power supply board in the base of the

enclosure. FIRST, disconnect any wiring going to Iout#1. Then,

verify voltage across these wires is about 16-18 VDC when still

connected to the terminal strip on the front half of the enclosure.

If the BLUE and WHITE wires are not connected to the terminal

strip on the front half of the enclosure, the voltage across them

should measure about 29 VDC.

4. If analyzer does power up with a display, use the “Simulate”

feature to check operation of the analog outputs (and relays

contacts with a DVM.)

5. Check sensor power circuits. With a DVM, verify between -4.5

and -5.5 VDC from sensor connection terminals WHITE (+) to

BLACK (-). Then verify between +4.5 and +5.5VDC from

GREEN (+) to BLACK (-).

6. Check TC drive circuit. Place a wire-short between the RED

and BLACK sensor terminals. With a DVM, measure the

voltage between the BLACK (-) and BROWN (+) sensor

terminals to verify that the TC drive circuit is producing about -

4.6 to -5.5 VDC open-circuit. Remove DVM completely and

connect a 1000 Ohm resistor across the BLACK to BROWN

terminals. The temperature reading on the front LCD should

display approximately 0°C and the dissolved oxygen reading

should display approximately 0 ppm.

10.31 Display

Messages

The DOTX-45 Series instruments provide a number of

diagnostic messages which indicate problems during normal

operation and calibration. These messages appear as prompts

on the secondary line of the display or as items on the Fault

List.

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Dot-x SERIES Spécifications Page 61