Metrohm 767 Calibrated Reference - Manual (Page 10)

3 Procedure for checking instruments
6
767 Calibrated Reference Instructions for Use
3 Procedure for checking instru-
ments
3.1 Basics
The 767 Calibrated Reference is connected instead of the sensors, if
possible by means of the original sensor cable. If this is not possible
(e.g. for electrodes without a plug-in head) a list of suitable cables can
be found in the appendix, see chap. 5.2.
Each instrument can be checked with the Calibrated Reference within
the normal operating program and therefore also with the worked-out
methods. This has the advantage that methods and selected function
runs can be tested at the same time.
On the other hand the Instructions for Use of most instruments contain
a so-called diagnosis instructions, selective instructions for checking
the functioning of the instrument if malfunctioning is suspected. This ty-
pe of check has the advantage that practically no (or only a very basic)
knowledge of operating the instrument is required. In addition, checking
the instrument by using the diagnosis instructions is usually significantly
faster.
This operating instructions for Calibrated Reference 767 are instructions
for checking the Metrohm instrument within the normal operating pro-
gram. As the very large range of instruments means that for individual
instruments many different names and operating structures may have
been used, these instructions should therefore be interpreted logically.
It is not absolutely necessary to firmly screw down the electrode cap at
sockets (4), (5), (6); plugging it in is quite adequate.
3.2 pH Meters and Titrators
Place the Calibrated Reference on the bench near the sensor. Ensure
that light is not hindered from reaching the solar cell (no shadows from
cables or accessories). If necessary switch on the room lighting.
On the instrument to be tested the slope must be set to 1, pH
as
to 7 and
the measuring temperature to 25 °C for measuring the pH.
Please note:
• On the basis of the pH calibration the pH is determined from the
measured potential value. The pH checked here is therefore chiefly
relevant as a functionality check.
• If the endpoint is evaluated from a curve in a titration, the absolute
measured potential or pH value is not relevant.
• With KF titrators this check should be evaluated as a functionality
test.