Hach Ultra ORBISPHERE 3624, Operator'S Quick Manual

Page 9

The following table lists possible measurement errors, which could be caused by poor handling of the
instrument and/or identifiable installation conditions.

Measurement Troubleshooting

Symptom

Probable Cause

Corrective Action

Expected Result

Message 

Out

Sensor not connected

Check sensor cable 

connection (at sensor and 

instrument end)

Measurement should return after 

approximately 20 seconds

Message 

Prg

(CO

2

)

Purge pressure too low or 

wrong purge gas

Restore correct purge pres-

sure and gas (refer to the 

TC 

Sensors - Maintenance & 

Installation Manua

l for 

details). Push the small plas-

tic tube firmly into the purge 

exit and check purge flow rate 

(over 3 bubbles per second.) 

Check voltage in continuous 

purge mode.

In continuous purge mode, 

voltage should be in the range 

-2.5V to +4.5V. If purge flow rate 

is too small, or if voltage remains 

above 4.5V, contact your 

Orbisphere agent

Damaged sensing 

element caused by 

mishandling during 

membrane replacement

For experienced 

service 

personnel only

: Remove 

membrane and support. 

Check for broken wires of the 

thermal conductivity chip 

under microscope

Contact your Orbisphere agent

System does not 

start: No display 

or backlight

Improper line voltage

Check instrument voltage

Select proper voltage (115V or 

230V) on power supply card

Blown fuse

Unplug instrument and 

replace blown fuse. 

Instrument should start up. If not, 

or if fuse blows again, contact 

your Orbisphere agent

High sample 

temperature

Blockage of sample flow 

causing heat buildup from 

pump

Check outlet of sample flow 

for blockage. If a check valve 

is in use, verify proper 

orientation

Temperature should decrease as 

normal sample flow resumes

Voltage drift 

during 

measurement 

(CO

2

)

Purge gas pressure too 

low

Set 2 bar gauge pressure or 

adjust pressure in order to get 

over 3 bubbles per second 

from exit tube

Measurement will return to 

expected value

Low reading 

(CO

2

)

Leak in purge inlet line

Check line for leaks with 

soapy water

Expected reading

High reading 

(CO

2

)

Erroneous calibration in 

gas with a wet membrane 

protection grill

Recalibrate in liquid, or, 

dry out the membrane and 

calibrate in gas

Expected reading

Totally erratic 

readings (CO

2

)

Water condensation into 

the thermal conductivity 

element due to purge 

failure or humid purge gas

Blow 

dry

 purge gas in "contin-

uous purge mode" overnight. 

Resume measurement mode.

In most cases, sensor operates 

properly. But condensation may 

result in serious damage, 

requiring service