User manual HANNA INSTRUMENTS BL 7916

[. . . ] Instruction Manual BL 7916 · BL 7917 pH and ORP Measuring & Dosing System www. hannainst. com Dear Customer, Thank you for choosing a Hanna product. If you need additional technical information, do not hesitate to e-mail us at tech@hannainst. com. These instruments are in compliance with the directives. PRELIMINARY EXAMINATION Remove the pump from the packing material and examine it carefully to make sure that no damage has occurred during shipping. Each pump is supplied complete with: · discharge and suction valves · LDPE tubing, 7 m (23') · power cord · instruction manual Note: Save all packing material until you are sure that the pump functions correctly. [. . . ] If it opens, the unit will not pump even if the controller commands it. 19 TERMINAL CONNECTIONS BL 7916 18 For example, a level controller can be placed in the tank of the liquid being dosed so that the pump is stopped when the chemicals are exhausted. SETPOINT ADJUSTMENTS · Move the display selector switch to SET. · With a small screwdriver adjust the SET COARSE trimmer to display a value close to the desired setpoint e. g. 7. 00. MANUAL An auxiliary switch can be connected to these terminals to force the unit to pump whatever value is measured by the controller. This might be needed for example when the pump needs to be primed. AUXILIARY CONTACT The controller can drive a relay when the measure overtakes the setpoint. The contact available on the terminals can be normally open or closed. It can be used as a switch to drive an external mixer when the pump is dosing, or can activate an auxiliary pump or any other device. With BL 7916, the contact can be selected to remain open when the pH value is within the set limits (the pump is not dosing) and closed when the pump is dosing or viceversa. By shorting the Common (middle) terminal with the NO or NC terminal on the driving circuit inside the controller section, a normally open or a normally closed state can be achieved, as shown below: · Adjust the SET FINE trimmer to display the exact setpoint value. · Once the desired setpoint is achieved, move the display selector switch back to MEASURE. ACID OR BASE SELECTION (BL 7916 only) If an acid chemical is to be dosed, move the ACID/BASE switch to ACID. This means that the pump will dose when pH measurements are higher than the setpoint. If an alkaline chemical is to be dosed, move the ACID/BASE switch to BASE. This means that the pump will dose when pH measurements are lower than the setpoint. ALARM CONTACT If the reading drifts from the setpoint by more than ±2. 00 pH in BL 7916 and ±200 mV in BL 7917, an external alarm can be activated. No power is supplied through the system and it is an open/closed contact only. With BL 7916, the contact can be selected to be closed when the alarm is activated and open when the alarm is off or viceversa. Short the middle terminal located on the driving circuit inside the controller section with the NO or NC terminal (see above). REDUCING OR OXIDIZING SELECTION (BL 7917 only) If a reducing chemical is to be dosed, move the RED/OXID switch to RED. This means that the pump will dose when redox measurements are higher than the setpoint. If an oxidizing chemical is to be dosed, move the RED/OXID switch to OXID. This means that the pump will dose when the redox measurements are lower than the setpoint. The wires and cables needed for all connections can be fed through the two cable fittings located below the terminals. It is important to attach these cables properly because pump vibrations could loosen them. Replace the transparent cover and fasten the screws. 21 4-20 mA ISOLATED OUTPUT A 4-20 mA proportional output is available in these connections: 4 mA=0 pH; 20 mA=14 pH (BL 7916) and 4 mA=-999 mV; 20 mA=+999 mV (BL 7917). The output is optically isolated. 20 pH CALIBRATION BL 7916 only: · Ensure that the display selector switch is set to MEASURE and dip the electrode tip in a neutral buffer solution (pH 7. 01). TROUBLESHOOTING GUIDE ELECTRICAL The pump does not operate when turned ON: · Check the power supply and connections. Voltage should be between 100 - 130 VAC for 115 V models and between 200 - 250VAC for 230 V models. [. . . ] To make correct redox measurements the following conditions must prevail: ­ The surface of the electrode must be cleaned and smooth. ­ The surface of the electrode must undergo a pretreatment in order to respond quickly. Because the Pt/PtO system depends on the pH, the pretreatment of the electrode may be determined by the pH and the redox potential values of the solution to be measured. As a general rule, if the ORP mV reading corresponding to the pH value of the solution is higher than the values in the table below, an oxidizing pretreatment is necessary; otherwise a reducing pretreatment is necessary: pH mV pH mV pH mV pH mV pH mV 0 990 1 920 2 860 3 800 4 740 5 680 6 640 7 580 8 520 9 460 10 400 11 340 12 280 13 220 14 160 30 Reducing pretreatment: immerse the electrode in HI 7091 solution for a few minutes. [. . . ]