Hach 2100P ISO Manual page 7

CERTIFICATION,
required to correct the interference at his own expense. The following
techniques of reducing the interference problems are applied easily.
1. Disconnect the external power supply or remove the batteries from
the 2100P ISO Portable Turbidimeter to determine whether it is the
source of the interference.
2. Move the 2100P ISO Portable Turbidimeter and its power supply
away from the device receiving the interference.
3. Move the device receiving the interference to a different location.
4. Try combinations of the above.
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