Manual Instrument Zeroing Procedure - In-situ ChemScan mini UV254 Installation, Operation And Maintenance Manual

Manual Instrument Zeroing Procedure

The ChemScan UV254 Analyzer must be zeroed occasionally to correct for drift and flow-cell
fouling. The analyzer will automatically perform an Auto-Zeroing Operation on a preset interval (as
set in the SETUP menu). However, it is important to periodically perform a Manual Zero Operation
to track the indicator numbers. This procedure simply involves rinsing the flow-cell with deionized
water, initiating a zero reading and testing the zero.
Items Required:
1 gallon of deionized water
Interrupt on-line mode:
Press the Main Menu key on the keypad. If a security code is programmed, the following message
will appear:
ENTER SECURITY CODE
Enter the current security code followed by the ENTER key and the Main Menu will be displayed:
1) ONLINE 3) CLEAN
2) SAMPLE 4) SETUP
Instrument Zeroing:
Press 2 for ZERO. The following message will be displayed:
1) MANUAL
2) AUTO
Selection of 2) AUTO will cause the system to immediately initiate an auto zero cycle. The
instrument will automatically flush with DI water, take a reading, compare the values to certain set
points, determine if cleaning is necessary, auto clean, re-zero and re-test. For details concerning
the autozero cycle, refer to the Selection of 1) MANUAL ZERO will require the operator to manage
the zeroing procedure and to interpret the indicator results. This zero once saved, serves as a
point of reference for internal diagnostics.
Press 1 for MANUAL ZERO. The following message will be displayed:
NEW: [XXXX] OLD [XXXX]
+ OR -, Zeroing Pump On/Off
Using the + key to begin flushing the deionized water. Allow the water to flush for 2 minutes and
press the - key to stop flushing; wait 30 seconds for the water to settle. Press ENTER to take the
reading. The instrument will read the deionized water and store the reading as a zero. The new
zero value will be displayed on the right left of the top line. The previous zero displayed to the left.
Using the + and - keys to control the pump, allow deionized water to flush for 8-10 seconds.
The Zero Value should be above 0.500. If not, manually clean the flow-cell. If the reading varies
by more than 0.005, flush again, pause for 10 seconds, and observe again. Continued noisy zero
indicates there may be loose material in the flow-cell, which must be removed by following the
cleaning procedure.
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