Chemtrac HydroAct HA4, User Manual

Page: 53 / 97

3.1 UV254 Sensor 53
Conversion values here provide information about the sensor environment (temperature and
humidity) and detector readings used to calculate the UV absorbance and transmittance.
There are 6 values found in this sub menu including; raw Lamp and Water readings, and internal
Temperature and Humidity. These values can be used to help determine how the system is performing.
If all the numbers displayed are 0 then this indicates the system did not start up correctly
(refer to the diagnostics LEDs). If Lamp and Water numbers are 0 but humidity and tem-
perature data appears to be correct then this indicates a communication problem with the
sensor board located on the rotating assembly. See troubleshooting section 3.1.6 for fur-
ther details.
Lamp Numbers
Lamp numbers are not affected by sample water absorbance as they are a direct reading of the
lamp output. Long and short readings should be within 20 points of each other and they should not
fluctuate by more than 20 points after the sensor has warmed up. If they fluctuate much more than this
it may indicate an issue with the map or with the lamp sensor.
If lamp numbers are too high this may indicate the current lamp is brighter than previous lamps. If
this is the case, contact your supplier. If the lamp numbers are too low then this usually indicates the
lamp needs to be changed. It is recommended to change the lamp every 18 months, but a warning will
appear on the display screen when the lamp starts to get low and needs replacing.
If a new lamp is installed and the lamp numbers are still too low then this may indicate that a new
lamp has lower output that the previous lamp. If the lamp reading is much lower than 2000 and the
lamp is new this may indicate a faulty lamp (perhaps damaged during shipping).
Water Numbers
Long and short readings are dependent on the absorbance of the sample water stream. If either or
both water values goes below 100 (and the lamp numbers are within correct range) then either the
sample is close to the top of the measurement range of the instrument, or the sample cell needs to be
cleaned.
With DI water in the flow cell, the Water values should be within 200 points of each other. If they
are much further apart than that, cleaning should be performed as this may indicate fouling or water
scaling of the flow cell. After cleaning and flushing with DI water, the water numbers can be checked
again to make sure the cleaning was sufficient.
Temperature and Humidity
The internal temperature should be kept below 50°C, the system will alarm if this temperature is
reached. If this does happen it may indicate that the sensor should be moved to a cooler location.
Humidity should be kept as low as possible especially when the sample water is cold as condensation
can form on the flow cell which can severely affect accuracy.