Hanna Instruments HI 8711 - Manual (Page 22)

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• •• •• The HI 8710 models are single dosage
controllers with acid/alkaline selection.
If acid dosage is needed (e.g. in chromium
VI reduction), leave open the ACID/ALK.
selection terminals (4 and 5), while for
alkaline dosage (e.g. in cyanide oxidation), make a short circuit
across the ACID/BASE selection terminals (4 and 5) with a jumper wire.
• •• •• The HI 8720 models are single dosage controllers with oxidant/
reductant selection.
If oxidant dosage is needed (e.g. in cyanide
oxidation), leave open the OXID/RED. selection
terminals (4 and 5). The dosing is activated
when the reading falls bellow the setpoint
value. For reductant dosage (e.g. in chromium
VI reduction), make a short circuit across
the OXID/RED. selection terminals (4 and 5) with a jumper wire.
The dosing is activated when the reading exceeds the setpoint value.
• •• •• SET contacts (HI8710 and HI8720) (see
picture terminals 1, 2): these contacts (max.
2A, 240 V) are used to connect the dosing
pump, and act only as a switch for the
power to the drive.
• •• •• ACID contacts (HI 8711) (see picture,
terminals 1 and 2): these contacts are used
to connect the dosing pump for acid, and
act as a switch for the power to the drive.
Connect the “+” wire of the recorder to the terminal 1 on the
instrument and the other wire (common) to terminal 2 for 4-20
mA recorder output or to terminal 3 for 0-20 mA recorder output.
Note: Only one recorder output connection is possible. In order to
avoid malfunction leave the unused terminal unconnected.
• •• •• Pt100 terminals: these contacts are used to
connect the Pt100 temperature sensor for
automatic temperature compensation of pH
readings. If temperature compensation is not
required, connect a 110 Ohm/0.25W resistor
across the terminals (equivalent to a fixed
temperature of 25°C/77°F).
Connect the Pt100 terminals to terminals 3 and 4. In case the
wires are shielded, connect the shield wire to terminal 2.