Hanna Instruments Pool and Spa Controller BL-121-20

Hanna InstrumentsSKU: BL-121-20

Sale price£1,744.55

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BL-121-20 includes all the advantages of the BL-121-10 as well as an optional flow cell for ease of maintenance. The bypass flow cell allows for calibration and maintenance of the probe without the need to shut down the recirculation pump. Ideal for swimming pools, hot tubs and spas.

The BL-121 Swimming Pool Controller is a complete system designed for maintaining swimming pool, hot tub, and spa disinfection water quality.

The controller is available in two versions:

    • Optional bypass flow cell included (BL-121-20) - ease of maintenance enhanced by allowing calibration and maintenance of the probe without the need to shut down the recirculation pump
    • Inline system (BL-121-10) allows for direct installation of probe and chemical injection fitting into existing piping.

Key features:

Multi-coloured LED indicators for dosing
Meter status and service
USB Connectivity
Real-time graph display
Automatic logging
Programmable alarms
Password protection


pH range:0.00 to 14.00pH

pH Resolution:0.01pH

pH Accuracy (@25°C: +-0.05pH

pH Calibration:pH buffer calibration automatic, two-point (4.01, 7.01, 10.01pH); pH process calibration: one-point, manual input

pH Dosing: Proportional with adjustable set point and proportional band; delay to start at power-on and overdosing protection

mV range: +-2000mV

mV Resolution: 1mVmV

Accuracy @ 25°C: +-5mVORP (mV) calibration one-point, manual input

ORP Dosing: Proportional with adjustable set point and proportional band; delay to start at power-on and overdosing protection; pH dosing interlocked

°C range: -5.0 to 105.0°C°

C Resolution: 0.1°C°

C Accuracy @25°C: +-1°C

Temperature Compensation: automatic, -5.0 to 105.0°C for pH

Pump control: Automatic and manual modes; adjustable flow rate from 0.5 to 3.5L/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 seconds sampling interval; all data.csv files are transferred by USB flash drive

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 set up

Password Protection: Set up, calibration and log recall options features are password protected

Storage interface: USB

GLP: pH/ORP calibration information including date and time for pH/ORP sensors

Alarm Relay Output (1): SPDT 5A/230 VAC; activated by pH/ORP/temperature selectable alarm conditions

Analogue Outputs (3): 4 to 20mA, sourcing configurable; output impedance ≤ 500 Ohm; accuracy < 0.5 % FS; galvanically isolated up to 50 V relative to earth ground

Auxillary Inputs (2): Low level in acid/base tank (contact open); low level in chlorine tank (contact open); hold input (contact open)

Digital Probe input (1): Galvanic isolated digital input HI-1036-1802 pH/ORP/temperature/matching pin combined probe with DIN waterproof connector

Power supply: 100-240 VAC

Power consumption: 10 VA

Environment: 0 to 50°C, max 95% RH non-condensing

Dimensions: 245 x 188 x 55 mm (73mm with pumps)

Weight: 1700g

More information:

BL-121 uses a multiparameter digital HI-1036-1802 probe that incorporates pH, ORP and temperature sensors along with a matching pin. All readings are measured within the probe and the data transferred to the controller by a digital connection.

A digital connection and matching pin provide for stable, reliable measurement. Without these two components, electrical noise from recirculation pumps and ground loops can interfere, causing erratic readings and premature probe failure.

BL-121 has two built-in peristaltic chemical feed pumps that are proportionally controlled with adjustable flow rates. One of the pumps is used to dose acid while the other is used to dose chlorine. The effectiveness of the available Chlorine, as determined by ORP, is inversely related to the pH value of the water. A pool with a fixed concentration of chlorine will show a decrease in ORP as the pH of the water increases.

BL-121 also features a dosing consent feature that will not dose chlorine until the pH value is first corrected. It is possible to have a low ORP value even though there is sufficient chlorine. The dosing feature avoids this situation as well as preventing chemical wastage and having a higher chlorine concentration level than desired.

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