Metrohm 767 Calibrated Reference - Manual (Page 13)

3 Procedure for checking instruments
767 Calibrated Reference Instructions for Use
9
3.2.4 Tolerances
Instruments with digital display:
Potential U ± 1 mV
pH value ± 0.02
Temperature ± 0.5 °C
Polarization functionality test
Instruments with analog display:
The tolerance is within the reading accuracy.
Example:
Theoretical potential value: 1200.7 mV
Instrument resolution: 1 mV, i.e. nominal pot. value =1201 mV.
The test is OK when the read off value lies between 1200...1202 mV.
If the measurements lie outside the tolerances they should be repeated
with the reference cable from the accessories case.
If the measurements are still outside the tolerance range please contact
your local Metrohm agency to arrange for the instrument to be serviced.
3.3 Conductivity meters
Read off and note the cell constant, the temperature coefficient, and the
temperature on the instrument to be tested. Then set cell constant and
temperature coefficient to 1 and the temperature to the reference tem-
perature valid for the instrument. Set the measuring frequency to
"automatic switchover".
Please note that a check carried out with this instrument and the diag-
nosis instructions (if available, see Instructions for Use of the Conduc-
tivity meter) may be quicker.
3.3.1 Conductance
carry out on instrument or sen-
sor: carry out on Calibrated Ref-
erence: compare dis-
play with remarks
1. screw off cable at sensor (for plug
head electrodes, otherwise use
corresponding accessory cable)
close cover place sensor in
storage tube
2. connect cable to socket (5)
3. set instrument to ‘conductivity’ func-
tion
cover always remains closed G value (5) compare with per-
mitted tolerance
4. connect cable to socket (6) G value (6) compare with per-
mitted tolerance
If further results are required:
5. remove measuring cable
remove measuring cable
6. connect conductivity measuring
input to Calibrated Reference with
2x banana cables (6.2150.000)
connect cable to sockets (1) (2)
connect cable to sockets (2) (3)
G value (1)(2)
G value (2)(3)
compare with per-
mitted tolerance