Metrohm 767 Calibrated Reference User Manual download pdf (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

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 22 23

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