Controller Overview
Multiple Configurations
The controller is available in one of
two configurations: an in-line model which allows for direct
installation of the probe and chemical injection fittings into existing
piping (BL120-10) or a panel mounted system with a bypass flow cell (BL120-20). The bypass
flow cell allows for calibration and maintenance of the probe without
having to stop the recirculation pump.
Digital Combination Probe
The HI1036-1802 is a digital probe that
measures pH, ORP, and temperature. This probe also incorporates a
potential matching pin. The pin is considered the āearth groundā
connection and is used to prevent ground loop effects from causing
erratic readings and damage to the system.
Dosing & Control
Peristaltic Dosing System
The BL120 is equipped with two peristaltic dosing pumps with
replaceable chemical resistant tubing. When using a diaphragm pump,
chlorine gas formed from outgassing can collect in the pump head
resulting in the pump losing its prime; the buildup of chlorine gas is
not a problem with peristaltic pumps that use rollers and tubing.
Proportional Pump Control
The BL120 features proportionally controlled dosing pumps. Based on
the sensitivity of the process to chemical addition, these controllers
allow the user to adjust a proportional band. This setting determines
the amount of time that the pumps are dosing as a percentage of the
deviation from the set point allowing for very fine control in
maintaining the desired set point.
Adjustable Flow Rate
The flow rate from the dosing pumps is adjustable from 0.5 to
3.5L/h. Larger bodies of water require more chemical to be dosed than
small bodies since it takes more chemical to realize a change in the
reading. The adjustable flow rate, like the proportional band, allows
for better control in maintaining a desired set point.
ORP Dosing Consent
With chlorine disinfection there is an inverse relationship between
pH and ORP. As the pH level increases, the ORP level decreases. The
BL120 utilizes a dosing consent feature that will not dose chlorine
until the pH value is first corrected since it is possible to have a
low ORP value even though there is sufficient chlorine. The dosing
consent feature prevents wastage of chemicals and avoids a higher than
necessary chlorine concentration.
Connections & Display
Circulation Pump MonitoringAn inline flow switch or a
mechanical relay connected to the recirculation pump power source
may be connected to the hold input of the BL120. With no flow or
when no power is applied to the recirculation pump, the hold
circuit disables the dosing pumps. This will prevent any dosing of
chemical when there is no movement of water in the system.
Multifaceted Display
The versatile display of the BL121
allows for three screen modes. The LCD can display all three
parameters at one time, a 3-second cycle of single parameters, or a
real-time plot screen with options for parameter selection,
zooming, and log recall.
Programmable Alarm System
Hanna controllers allow users to
enable or disable the low and high level of alarms for all
parameters. When an alarm is activated, all dosing will stop.
The alarm system also offers overdosing protection if the value
is not corrected within a specified time interval then the
meter will go into alarm status.
Multicolored LED Indicators
The BL120 offers multiple LED
indicators for status, servicing, and pump operation. The
STATUS LED changes color based on operational state; green when
setting are in range, yellow when user intervention is
required, and red for problems. The SERVICE LED indicates any
alarms and process errors experienced by the controller.
Communication & Security
Automatic Logging
The readings for each parameter are automatically logged every
10 seconds. A new log is started each time the instrument is
calibrated or at the start of a new day. Logged data include pH,
ORP, and temperature values, last calibration data, setup
configuration, and any event data. Each log is saved as a .csv file
for easy transfer.
USB Connectivity
For review and storage the users can easily transfer data to a
PC using a flash drive and the USB port.
Password Protection
Hannaās BL120 controller features a password protection solution
that offers restricted access to calibration, setup, and review of
logged data. The password can be set and enabled/disabled during
general setup of the instrument.
