Hanna Instruments HI 84185 - Manual (Page 21)

21
QUICK CHECK OF THE ELECTRODE SLOPE
• Connect the electrode and the reference electrode to the instrument.
• Press and hold down ESC, and HELP keys simultaneously and power on the meter. Wait
until the instrument enters in the reading check mode.
• Fill a beaker with 50 mL of deionized water and put a stir bar inside. Place the beaker in
its appropriate place on the instrument top.
• Put the electrode holder and insert the electrode and temperature probe in the solution. Add
2 mL of HI 84185-0 ISA buffer. Close all holes.
• Add rapidly 1 mL of HI 84185-1 Standard taking care to close all holes immediately after
addition. Wait for the reading to stabilize and record the mV value.
• Add rapidly 10 mL of HI 84185-1 Standard like before taking care to close all holes
immediately after addition. Wait for the reading to stabilize and record the mV value.
• The difference between the two recorded mV values gives the slope of the electrode. An
accepted value for this slope is -56±4mV.
• If sensor does not change mV the internal glass may have broken.
• Press ESC to leave the reading check mode.
PERIODIC MAINTENANCE
Inspect the electrode and the cable. The cable used for connection to the instrument must be
intact and there must be no points of broken insulation on the cable, or cracks on the electrode
stem or bulb. Connectors must be perfectly clean and dry. If any scratches or cracks are present,
replace the electrode. Rinse electrode with deionized water between samples and blot dry with
lab wipe or other soft disposable absorbent towelling.
STORAGE PROCEDURE
The HI 61101 probe can be stored assembled in HI 4001-45 Ammonia Conditioning and
Storage solution overnight or short term. Gently pull on the cable to compress the spring
mechanism thus permitting electrolyte to exchange from the bulk to the thin film between the
membrane and glass before resuming use. For storage over a week, disassemble the sensor
completely and rinse off the inner pH/ref assembly, the outer body and the membrane cap.
Discard membrane. Cover the glass tip with the protective cover used in shipment and store parts
securely in the original shipping box. When reassembling the sensor follow the Preparation
Procedure section.
MALFUNCTIONING
• No slope (meter always reads the same value):
Repeat the measurement with a fresh ammonia electrode.