HF scientific Micro200BW Turbidimeter - 0-100 NTU - Manual (Page 45)

MICRO 200 BW 0-10 & 0-100 NTU (05/05)
Rev. 3.4
8.0 OPTIONS
BACKWASH
8.1 INSTALLATION
8.1.1 Backwash Interface (Catalog No. 19275)
To monitor backwash using the MICRO 200 BW, one
backwash interface and one backwash sensor is re-
quired for each analyzer . Refer to figure 16 for the
outline of the backwash interface. Power requirements
are 12 VA at 110 - 120 VAC or 220 - 240 VAC. The
voltage may be changed using the selector switch lo-
cated inside the interface housing. See figure 17 for
details. The interface may be mounted up to 300 feet
(91.4 m) away from the backwash sensor. The signal is
sent to the MICRO 200 BW analyzer via BNC connec-
tors through up to 1000 feet (304.8 meters) of coaxial
cable (Catalog No. 20849). Refer to figure 15 for the
analyzer BNC cable connection.
Figure 15
Analyzer BNC Connection
8.1.2 Junction Box
This option, HF Catalog No. 19805, may be used to
extend the backwash sensor cable to a total length of 350
feet (106.7 meters), as measured from the sensor to the
backwash interface. The junction box is weather tight
and may be mounted outside. Refer to figure 18 for
outline dimensions. For wire connections refer to figure
19. Extension cable may be ordered using HF Catalog
No. 20848.
8.1.3 Backwash Sensor
There are two standard methods of installing this sensor,
channel mounting and extension handle mounting
(Catalog No. 50321). Both of these will be described
below. If alternate methods of mounting are required,
please consult HF scientific inc.
When choosing an installation site for the sensor there
are several things to consider. Since filters rarely will
backwash consistently or uniformly, a site should be
chosen that best averages the backwash water over the
cycle. The sensor should also be located as close to the
backwash filter as possible to reduce the time delay of the
water sample. This will give the operator a correct picture
as to how the backwash is proceeding and when it is
complete. Refer to figure 20 for sensor outline dimen-
sions.
8.1.3.1 Channel Mounting
This method can be used when the area above the end
of the channel is easily accessible. This allows cleaning
of the sensor or calibrating by lifting the sensor up by
its cable and lowering it back into place when you are
finished. Since the sensor is not affected by sunlight, a
light shield is not required. An installation kit is available
from HF scientific, HF Catalog No. 50345 which in-
cludes the sensor chamber, a stainless steel bracket, and
mounting clamps. The user must supply PVC piping,
bolts and anchors. Refer to Figure 21.
8.1.3.2 Extension Handle Mounting
This method allows the user to adjust the sensor position-
ing to optimize the sampled water. An installation kit is
available from HF scientific, HF Catalog No. 50356
which includes sensor end baffles, hose clamps, and a
pipe adapter. The user must supply the extension pipe
such as galvanized steel ½” to 1½” in diameter (12.7 mm
- 38.1 mm) and any additional mounting deemed neces-
sary for upper end.
1. The slot for the outlet baffle must be positioned in a
vertical axis at the top.
2. Remove all rough edges from the pipe to prevent
cable damage.
3. Attach the sensor to the pipe adapter with hose
clamps.
4. Sensor cable can be wrapped around the pipe. If
the pipe diameter permits, the cable can be threaded
through the pipe.
5. Don’t pull the cable too sharply through the pipe, use
a large radius bend instead.
In operation, some experimentation will be needed dur-
ing backwash to achieve optimal results. Note that
the adapter has a pivot to allow the sensor to lay parallel
to the bottom. Refer to figure 22.
8.2 BACKWASH SENSOR CONNECTIONS
The Backwash sensor is supplied with a 30 foot (9.1
meters) cable (Catalog No. 20853). This cable connects
at TB2 of the Backwash Interface. The cable should first
be inserted through the strain relief fitting of the case. At
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