Dosing & Control
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 setpoint 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 the 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.
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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 for 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 the general setup of the instrument.
| Specification Name | Detail |
|---|---|
| SKU | BL121 |
| pH Range | 0.00 to 14.00 pH |
| pH Resolution | 0.01 pH |
| pH Accuracy (@25°C/77°F) | ±0.05 pH |
| pH Dosing | proportional with adjustable set point and proportional band; delay to start at power-on and overdosing protection |
| ORP Range | ±2000 mV |
| ORP Resolution | 1 mV |
| ORP Accuracy (@25°C/77°F) | ±5 mV |
| ORP Dosing | proportional with adjustable set point and proportional band; delay to start at power-on and overdosing protection; pH dosing interlocked |
| Temperature Range | -5.0 to 105.0°C (23.0 to 221.0°F) |
| Temperature Resolution | 0.1°C (0.1°F) |
| Temperature Accuracy (@25°C/77°F) | ±1°C (±1.8°F) |
| Temperature Compensation | automatic, -5.0 to 105.0°C (23.0 to 221.0°F) for pH |
| Calibration | pH buffer calibration: automatic, two-point (4.01, 7.01, 10.01 pH)pH process calibration: one-point, manual input |
| 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 |
| 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 |
| Password Protection | setup, calibration and log recall options features are password protected |
| Connectivity | USB |
| GLP | pH/ORP calibration information including date and time for pH/ORP sensors |
| Alarm Relay Output | SPDT 5A/230 VAC; activated by pH/ORP/temperature selectable alarm conditions |
| Analog Outputs | 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 | low level in acid/base tank (contact open); low level in chlorine tank (contact open); hold input (contact open) |
| Digital Probe Input | 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°C (32-122°F); 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.) |
