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1. Introduction
The BB2 central unit is developed to make measurement easy. In combination with
different sensors BB2 is used to measure fiber and particle consistency in the pulp and
paper industry, or suspended solids, dissolved oxygen, pH, ORP and flow in water
treatment plants.
2. A few words about this manual
The manual primarily contains information about the BB2 central unit. The operation
and measuring principles of the sensors are described in the sensor manuals.
3. Design
The BB2 central unit is enclosed in a black plastic box, having a large graphic display
and only three buttons to operate it. The electronics has been designed to achieve the
highest reliability, and maximum ease of use. Measured values, settings and diagnostic
information is transferred to and from up to four sensors using digital communication
on a RS485-line. BB2 can be connected to a control or supervision system using
standard 4-20 mA analog signaling or a standardized fieldbus such as Profibus (option).
4. Working principle
BB2 is based on a powerful 16-bit microprocessor. The internal software uses a real-
time operating system, allowing multiple tasks to be carried out in “parallel”. One
process takes care of the display and the dialogs, one process is dedicated to handle
each attached sensor, and one task is taking care of all the housekeeping.
After power up, the software will initialize the functionality, and data structures, reading
information from a non-volatile memory. A welcome message is displayed for about ten
seconds, showing the software version and serial number of the BB2. The unit will then
start looking for sensors it already knows, and if found initialize them to start measuring.
Twice a minute the unit looks for unknown sensors, if one is found, BB2 will find out
the type and serial number, and open up a dialog box to let the operator select what slot
to use for the new sensor.
All configuration of BB2 and connected sensors are done in menus, when a menu is
opened on the display, the analog outputs of BB2 are frozen in order not to cause an
alarm in the control system during calibration or while parameters are being changed.
If a sensor is disconnected, the analog output for this sensor will be frozen until the box
is powered off, the sensor reconnected or the slot emptied.
Some sensors have automatic cleaning controlled by BB2, During, and a selectable time
after the cleaning, the outputs for the sensor being cleaned is frozen.
Some sensors has the possibility to save more than one calibration curve, e.g. to handle
different qualities of pulp. The calibration curve can then be chosen manually in the
menu, or automatic using digital inputs of BB2.
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