Metrohm 767 Calibrated Reference - Manual (Page 16)

4 Checking by means of the diagnosis instructions
12
767 Calibrated Reference Instructions for Use
4 Checking by means of the di-
agnosis instructions
For most Metrohm instruments the so-called diagnosis instructions can
be found in the Instructions for Use. These are intended to provide the
possibility of testing an instrument with real or suspected malfunctions
in a simple way.
Until now when checking the measuring inputs the difficulty was always
experienced that for the quantities ‘potential’ and ‘resistance’ there was
often no suitable source available in the laboratories. In addition these
could no longer be connected to the high impedance sockets of our in-
struments. This difficulty has now been remedied in an outstanding
manner by our 767 Calibrated Reference.
In the diagnosis instructions of previous instruments the measuring
source 767 Calibrated Reference for mV, pH, Ω, µS, °C is not men-
tioned. However, it is easy to see how the instrument is to be connected
from the diagnosis instructions. The operation of the Calibrated Refer-
ence is almost self-evident and it is not difficult to derive the way in
which it is to be used from section 1 of these Instructions for Use (plea-
se note that polarization current and potential sources can be very
quickly checked in the diagnosis: connect sensor cable to socket (5),
close cover, start test, read off !)
For measurement at the differential inputs (e.g. Ind I / Ind II) it should be
noted that both inputs cannot be connected to the Calibrated Refer-
ence at the same time as this would short-circuit the output sockets.
This problem can be avoided by actually connecting both inputs, but al-
ternately shorting one of the two inputs with cable 3.496.5070. How-
ever, should this appear to be expedient under exceptional circum-
stances, two different, but separately earthed instruments can be
connected to the same Calibrated Reference (to sockets (5) and (6)).