Bürkert’s sensors, which operate with
much smaller volumes of sample fluid
than traditional equipment can offer more
accurate data and greater operating life.
TURBIDITY
Traditionally, turbidity sensors are
calibrated using formazine, or verified with
a verification block and probe. Both have
their downsides, formazine is a carcinogen,
so in most cases the probe is sent back to
the manufacturer to be tested and cleaned.
The verification block and the probe
equipment on the other hand is difficult to
store and use in the field while maintaining
accuracy.
Bürkert has done away with both of
these less than ideal methods in favour of
repeatable, accurate test processes using a
dedicated plug-in calibration tool.
The added difficulty with turbidity
calibration is that any bubbles, however
small, will interfere with the result. Bürkert’s
in-field calibration tool takes account of this
and ensures continued accuracy without
the need to send sensors back to the
manufacturer.
PH
Traditional pH probes should not be
allowed to dry out, either during storage or
operation, and they have a defined shelf life
of approximately one year. With the Bürkert
solution, there is no glass component
within the cube, so it can be stored
indefinitely, and the calibration process is
straightforward and quick.
The calibration process for pH, ORP and
conductivity cubes uses a hand-held module
that connects into the bus network or via a
laptop, with the onscreen guide providing
step-by-step instructions. The calibration
module contains a standard fluid, for example
at pH 5 or pH 7, which is drawn into the
analysis cube. By following the steps any
offset between the standard and the cube
reading is addressed, and the process is
complete.
CHLORINE
The amperometric chlorine MEMS sensor
chip used by Bürkert is not affected by
chloramines, providing true chlorine analysis.
Other major benefits are the fact that the
sensor cubes are not reagent-based, they do
not use an electrolyte or a membrane cap as
traditional probes do, neither is there a need
to maintain a gold electrode with abrasive
paper, so the maintenance requirement for
this system is greatly reduced. The calibration
process involves taking a reading from the
display in parts per million (ppm), and a
sample of the water at the same time and
using a DPD1 photometer reference test
for free chlorine. This is a universal test for
chlorine that is used all over the world to
quickly establish the offset and recalibrate
the cube.
CONNECTIVITY
Each of these cubes can be arranged as
required, depending on the application.
Multiple sample lines can be added to
one central analysis station, or several
remote stations can be connected using
any of the common industrial networking
communication protocols.
Depending on the needs of the system, the
analysis cubes can be connected directly to
a PLC, which can perform the datalogging
function as well as using the analysis data to
make changes in the process. Used in either
a compact system or a panel-built system,
there is a direct connection between the
cube and the output card.
Therefore, if the display or the datalogger
fails for any reason, the cube continues to
operate and transmit its data to the control
network. Each sensor cube has its own
output card, so if one fails, all the other cubes
continue to operate, while the failed card
issues a warning message to allow a repair to
be made.
COMPACT SOLUTIONS
This simple solution offers many advantages
to the water industry as well as the food and
beverage sector. Downtime for calibration is
kept to an absolute minimum, site operatives’
safety is assured and the costs for calibration
are also minimised. Integration with
existing process control systems is relatively
straightforward, however Bürkert can provide
on-site support ranging from specification
advice to a full turnkey installation and
commissioning service.
The combination of modular cubes, simple
calibration, operational flexibility, reliability
and a very compact footprint means that
Bürkert’s Type 8905 Online Analysis System is
setting the standard for clean water quality
analysis.
www.burkert.co.uk
Issue 39 PECM
83