BL121-20 pH/ORP Swimming Pool Controller (Flow Cell)

Manufacturer: HANNA Instruments Inc.

Order number: BL121-20


Delivery time approx. 2 to 4 weeks

S$ 2,248.00 *

Product information "BL121-20 pH/ORP Swimming Pool Controller (Flow Cell)"

Control with Confidence


The BL121 Swimming Pool Controller is a complete system designed for maintaining swimming pool, hot tub, and spa disinfection water quality. The BL121 is available in two configurations. The basic version is the in-line model which allows for direct installation of probe and chemical injection fittings into existing piping. The other version is a panel mounted version with a bypass flow cell. The bypass flow cell allows for calibration and maintenance of the probe without having to shut down the recirculation pump. Additional features of the BL121 include LED indicators for dosing, meter status and service, real-time graph display, programmable alarms, and password protection.

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 (BL121-10) or a panel mounted system with a bypass flow cell (BL121-20). 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 “earth ground” connection and is used to prevent ground loop effects from causing erratic readings and damage to the system.

Peristaltic Dosing System

The BL121 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 BL121 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 BL121 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.

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.

Analog Output

The BL121 offers three 4-20 mA outputs for pH, ORP, and temperature. Each output may be disabled or connected to an external recording device and is adjustable to be proportional to the measured value. For greater flexibility and better resolution, the analog output can be scaled; users can define any two points within a parameter range to correspond to the analog output span. This adjustment allows better resolution in the range of interest.

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

Hanna’s BL121 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.

pH Specifications

pH Range 0.00 to 14.00 pH
pH Resolution 0.01 pH
pH Accuracy ±0.05 pH
pH Calibration pH buffer calibration: automatic, two-point (4.01, 7.01, 10.01 pH)
pH process calibration: one-point, manual input
Temperature Compensation automatic, -5.0 to 105.0ºC (23.0 to 221.0ºF) for pH


ORP Specifications

ORP Range ±2000 mV
ORP Resolution 1 mV
ORP Accuracy ±5 mV
ORP Calibration ORP (mV) calibration: one-point, manual input


Temperature Specifications

Temperature Range -5.0 to 105.0ºC (23.0 to 221.0°F)
Temperature Resolution 0.1°C (0.1ºF)
Temperature Accuracy ±1ºC (±1.8ºF)



pH Dosing proportional with adjustable set point and proportional band
delay to start at power-on and overdosing protection
ORP Dosing proportional with adjustable set point and proportional band
delay to start at power-on and overdosing protection
pH dosing interlocked
Alarms high and low with enable/disable option for all parameters
alarm is triggered when 5 consecutive readings are over/under threshold
Alarm System intuitive alert system based on LEDs
alarm filtering options
alarm relay control based on user setup
Alarm Relay Output (1) SPDT 5A/230 VAC
activated by pH/ORP/temperature selectable alarm conditions
Analog Outputs (3) 4 to 20 mA, sourcing, configurable
output impedance ≤ 500 Ohm
accuracy < 0.5 % FS
galvanically isolated up to 50 V relative to earth ground
Auxiliary Inputs (3) low level in acid/base tank (contact open)
low level in chlorine tank (contact open)
hold input (contact open)
Pump Control automatic and manual modes
adjustable flow rate from 0.5 to 3.5 L/h
Log Feature automatic logging of pH, ORP, and temperature measurements, GLP and events including alarms, errors and power failure
capacity for 60 days with 10 second sampling interval
all data .csv files are transferred by USB flash drive
Password Protection setup, calibration and log recall options features are password protected
Storage Interface USB
GLP calibration information including date and time for pH and ORP sensors
Digital Probe Input (1) galvanic isolated digital input HI1036-1802 pH/ORP/temperature/matching pin combined probe with DIN waterproof connector
Power Supply 100 - 240 VAC
Power Consumption 10 VA
Environment 0 to 50 ºC (32-122 ºF); max 95% RH non-condensing
Dimensions 245 x 188 x 55 mm (73 mm with pumps);
9.6 x 7.4 x 2.2” (2.9” with pumps)
Weight 1700 g (60 oz)
Ordering Information  BL121-20: Swimming Pool & Spa Controller with panel mounted flow cell, HI1036-1802 combined pH/ORP/temperature digital electrode, with probe fittings and chemical injectors




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