Metrohm 751 GPD Titrino - Manual (Page 200)

4.2. Diagnosis
751 GPD Titrino
197
6 Analogue input test
• Press <7>.
analog input test 1...5
6.1 Examination of highly insulated measuring inputs
• Connect ‘Ind I’ measuring input to a voltage calibrator (e.g. Metrohm 642 pH simulator) by
means of a highly insulated cable (e.g. 6.2108.060). Set calibrator to 0 V.
• Press <1>.
Input 1 0.0 mV
Tolerance: ± 0.5 mV
• Set the calibrator voltage, on setting 'low ohmic' (with 642 = ~ 0.002 M Ω ) to different val-
ues (e.g. +1500 mV) and compare with the displayed value.
Tolerance (with ± 1500 ÷ 2000 mV) ± 1 mV. Be aware of the calibrator's tolerance.
• Set simulator to high ohmic condition (with 642 = 1000 M Ω ).
The displayed reading may vary slightly only (with 1500 mV ó 1 mV)
• Press .
analog input test 1...5
• Disconnect simulator from ‘Ind I’ input and connect to ‘Ind II’ input.
• Press <2>.
Input 2 XX mV
• Carry out the same measurements as with Input 1.
• Press .
analog input test 1...5
• Short-circuit input ‘Ind I’ (e.g. with cable 3.496.5070).
• Press <3>.
Input 1-2 XX mV
The differencial voltage between inputs ‘Ind I‘ and ‘Ind II’ is displayed.
Example: 0 - (+)1500 mV = -1500 mV
• Remove cables from the inputs ‘Ind I’ and ‘Ind II’.
• Press .
analog input test 1...5