Jenway 3540 - Manual (Page 66)

7.20 mV Measurement
The mV measurement mode can be used for Redox (ORP) measurement as well as
probe diagnostics. The mV mode can be accessed by pressing the up or down arrow
key when the pH tab is highlighted in the main measurement screen. In many
instances calculation and comparison are made easier by calibrating out any probe
off-set, this can be done using the Relative mV (Rel mV) function. This function can
pull in to zero + or – 1999.9 mV which is half the full-scale range.
An absolute mV reading of 166.9mV is set to zero in Relative mV mode by pressing the CAL key
To calibrate out any mV off-set simply press the CAL key when the mV reading is
stable and the endpoint indicator is displayed. The reading will be set to zero and the
Relative mV indicator will be displayed. Any further readings taken will be based on
this new zero level. To return to Absolute mV measurement press the CAL key again.
7.30 TDS
Measurement
Total Dissolved Solids can be measured as a function of conductivity, a range of
factors have been prescribed by various national and trade bodies for the correlation
of conductivity to the TDS value of various sample types. This factor is commonly
referred to as the EC ratio and can be set in the conductivity calibration set up menu,
see section 4.12
TDS value in g/l replaces conductivity display
To display the TDS value press the up or down arrow when the Cond tab is
highlighted to change the tab indication from Cond to TDS. Each channel has its own
endpoint indicator and the reading for individual channels should not be recorded until
its endpoint indicator is displayed.
Results can be stored in the internal memory using the powerful data logging
functions, see section 3.3. Simply pressing the Store [STO] key will save the result to
the next available location along with the date, time and any batch code entered in
the set up menu. Alternatively the data logging function can be set to automatically
store or print the results when the endpoint indicator is displayed saving any
intermediate key press between samples.