Why does the 924x Sodium analyzer reject calibration within eight minutes?

Document ID

Document ID TE4021

Published Date

Published Date 02/27/2018
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Question
Why does the 924x Sodium analyzer reject calibration within eight minutes?
Summary
Rejection of calibration on 924x Sodium analyzer after eight minutes autocalibration
Answer
The instrument must read less than 1/1000th the value of the undiluted calibration standard during the background measurement (the first seven to eight minutes of the calibration cycle) or it cannot perform the autocalibration (cal known addition) function.

Acceptable background range based upon calibration standard values:
<10 ppb for 10 ppm standard
<100 ppb for 100 ppm standard
<1,000 ppb for 1,000 ppm standard

See below for the calibration sequence of events.

Sequence of Events During a Calibration:
Time Elapsed     Event   
Start                   Background Check - Make sure water is below 10 ppb
8 min                 
Reactivation - Background reading displayed and reactivation pump on
13 min               
Flush - Conditioning pump cycles and the measurement block flushed
23 min               
Pre-pump Standard - Calibration pump cycles to remove air from line
24 min               
Drain Reservoir – Sample valve is off and drain pump turns on
27 min               
Measure Flow – Sample turns on and flow is measured
29 min               
Sample Off – Sample valve shuts off and conditioning pump cycles 80 times
31 min               
Standard Added – Calibration pump cycles, about 40 times (2 ml)
33 min               
Mix and Read – Stir motor on and conditioning valve cycles
39 min               
Reading Displayed – Drain pump turns on and standard 1 displayed
41 min               
Sample On – Reservoir filled
44 min               
Sample Off – Sample valve shuts off and conditioning pump cycles 80 times
46 min               
Standard Added – Calibration pump cycles, about 400 times (20 ml)
51 min               
Mix and Read – Stir motor on and conditioning valve cycles
57 min                Reading Displayed – Standard 2 reading is displayed and instrument displays slope and offset.  Indication of successful/unsuccessful calibration is also shown.

 

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