BL-121-20 Pool and Spa Controller

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
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.
HI-1036-1802 Multiparameter Digital pH, ORP, Temperature Probe
HI-1036-1802 is a digital probe that measures pH, ORP, and temperature. This probe also incorporates a potential matching pin. The matching pin is considered the ‘earth ground’ connection and is used to prevent ground loop effects from causing erratic readings and damage to the system.
pH glass has been chosen to produce stable quick equilibration even in low conductivity waters. Additionally, the pH sensor is designed to produce a mV value near pH 4 (not pH 7 like typical sensors) should it stop working. A broken pH electrode that produces mV value near pH 7 would produce an alarm state and disable any pump activated.
The ORP sensing surface is a large smooth surfaced platinum band that encircles the circumference of the temperature probe. It is referenced to Ag/AgCl reference electrode (3.5M KCI).
The ORP and pH sensors and reference electrode all use a differential measurement technique designed to deliver accurate results under adverse conditions that may cause conventional pH probes to produce erroneous measurements.
The HI-1036-1802 probe with its differential amplifiers greatly reduces inaccuracies caused by ground loops which may exist between process and instrument grounds. With the differential technique, a ground loop current flows through the low impedance path of the matching pin and provides immunity to the measurement signals. In addition, the probe converts these measurements to a digital signal to eliminate noise and static due to high impedance signals carried by cable.
Both the HI-1036-1802 and the BL-121 Pool controller promote the health and safety of pool and spa water.