HF scientific Micro200BW Turbidimeter - 0-100 NTU - Manual (Page 46)

MICRO 200 BW 0-10 & 0-100 NTU (05/05)
Rev. 3.4
this point the outer jacket of the cable should be stripped
back about three inches. Care must be used to not nick
the wires under the jacket. Note that the sensor cable is
composed of two pairs of wires. Each pair consists of
two insulated wires and an uninsulated shield wire,
wrapped individually in a foil shield. The wire pairs are
RED & BLACK and WHITE & BLACK. The foil can
be unwrapped and removed, while keeping the pairs
together. The two shield wires should be wrapped
together. The remaining wires need to have the insula-
tion stripped back about ¼”. The sensor cable can now
be wired to the appropriate terminal block, using care
not to transpose the black wires in opposite pairs. Make
the following connections:
Terminal 1 White wire - white/black pair
Terminal 2 Black wire
Terminal 3 Uninsulated shields
Terminal 4 Red wire
Terminal 5 Black wire - red/black pair
8.3 BACKWASH SENSOR MAINTENANCE
Over a period of time contaminants may build up on the
flow through glass surface of the sensor. This may affect
the operation of the sensor. The sensor should be
cleaned periodically. A soft bottle brush can be used
with a mild solution of water and detergent followed by
a thorough rinsing with water. For optimal results, clean
the sensor each time before calibrating.
An indicating type desiccant can be seen through the
glass of the sensor. If no leaks are present, these beads
will be blue. If the beads are not blue, the sensor must
be returned to HF scientific for service.
8.3.1 Backwash Calibration
This procedure takes place through the Calibration
selection from the Utilities Menu. Numbers will be
displayed on the LCD (screen). These numbers repre-
sent frequencies adjusted so that 10KHz is represented
as 100%T. The numbers in the top center of the screen
show real time frequency and percent transmittance as
it is output from the sensor. The number to the right of
the 100%T is the frequency that was saved from the
previous backwash calibration. See page 16.
Follow this procedure:
1. Inspect the glass tube in the backwash sensor.
Clean the sensor in mild detergent and a soft bottle
brush, if required.
2. Insert the backwash sensor in a container of
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100 %T water, preferably the same water which
will be used for backwash.
3. Press the twice to highlight the Frequency
Column. Press the
to perform calibration.
(This is the only cal point necessary for backwash
calibration.)
8.4 BACKWASH ALARMS
To use the backwash alarms you must first enter the
backwash display, and then exit to the main menu.
Select F2 for alarms. The alarms may be set as shown
on page 17. Note that the alarms are set in percent
transmittance and that these alarm settings are unique
to the backwash function. These settings do not affect
previous turbidity alarm settings.
CAUTION: If either of these alarm contacts are wired
to a turbidity control function, set that
alarm to “off” to prevent accidental op-
eration during a backwash. Likewise, if
alarm contacts are wired to a backwash
control function, set that alarm to “off” to
prevent accidental operation during tur-
bidity measurement.
8.5 BACKWASH REMOTE SWITCHING
NOTE: This feature adds two attributes to the MICRO
200 analyzer:
1) The addition of an analog output either 4-
20mA or 0-10V while operating in the back-
wash mode.
2) The ability to switch, at a remote location,
between turbidity and backwash.
8.5.1 ELECTRICAL CONNECTIONS
8.5.1.1 Remote Switch
Connections are made at the analyzer terminal block J7
labeled MISC. INPUTS (SIGNAL). A dry (not pow-
ered) “A” contact connection between terminals 1 & 2
is required. With an open circuit between these contacts,
the MICRO 200 will operate normally. Closing this
circuit, while in the turbidity display, will cause the
instrument to change to the backwash mode.
8.5.1.2 Alarms
Two sets of user settable alarm contacts are provided
plus an additional sensor alarm. Separate Alarm set
points may be made in either turbidity and backwash
modes. Keep in mind that when you change modes these
F1