Metrohm 773 pH/mV Simulator - Manual (Page 7)

2.2 Aligning/Checking the pH
773 pH/mV Simulator
5
2.2 Aligning/Checking the pH
773 pH/mV Simulator
x100
x10
x1
-
-
14,3k PT1000 PT100 RE WE WE ON/OFF
pH U/mV
- +
20
6
4
2 18
16
14
12 10 8
0
+ +
0
20
25 40 60 80
100 C
1000 ~0,002
pH=7
U=0mV
i R /M
1. Connect the socket "WE" of the 773 pH/mV Simulator with the
measuring input of the instrument with the 6.2150.040 Cable.
For instruments with an E-plug (e.g. 670, 636) use the 6.2150.030 Cable.
For checking the instrument and its electrode cable:
Screw off the cable from the sensor and insert it in socket "WE" of the 773
pH/mV Simulator.
If you normally work with separate electrodes then remove the cable from the
reference electrode and insert it in socket "RE" of the 773.
2. Switch on the 773 pH/mV Simulator; the pilot lamp lights up.
3. Set slope = 1 and pHas = 7 on the instrument to be checked.
4. Set the instrument to be checked to "Measure pH".
5. Select "pH", (switch 6).
6. Set impedance switch R
i
to 0.002 M Ω .
7. Select the temperature on the 773 pH/mV (switch 7). It must be
the same as the measuring temperature of the instrument being
tested.
8. Set the required value with the measurement switch and read off
the measured value on the instrument being checked.
Compare this measured value with the value given in the table.
Please take into account both the resolution of your instrument’s
display and the information about tolerances given in the
‘Instructions for Use’ for your instrument.
9. Set impedance switch R
i
to 1000 M Ω . The measured value on the
instrument being checked should differ from the value obtained in
step 8 by less than pH=0.01.
Examples:
Set on pH Simulator Read off on instrument
pH=2, Ri= ≈ 0.002 M Ω pH=1.97
pH=2, Ri= 1000 M Ω pH=1.95
⇒ alignment poor, high-impedance OK.
Set on pH Simulator Read off on instrument
pH=2, Ri= ≈ 0.002 M Ω pH=2.00
pH=2, Ri= 1000 M Ω pH=1.95
⇒ alignment OK, high-impedance poor. Check the electrode cable!
Note: pH 7 can also be set directly with switch (9) (setting pH = 7).
6.2150.040 Cable