Hach 2100P Instrument And Procedure Manual page 64

SECTION 4,
9. Replace the battery(s) and battery cover.
10. Insert the 800 NTU formazin standard into the sample cell. Press
and hold
READ
software version number disappears from the display (for models
with serial numbers less than 920300000800,
continued
. Then press
I/O
READ
. Release the
READ
I
O
64
key after the
disappears).
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