Functional Safety Manual
for the Memosens transmitter Liquiline M CM42 SIL
Version:
Page:
2.0
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also need two buffer solutions, one with pH 7.0 and the other with pH 9.0 or 9.2.
You need a reliable ampere meter to measure the current at both current outputs. The
precision must be at least ±1mA.
Note!
The proof test can be done in the laboratory or "in process".
The procedure of the proof test is as follows:
(This is the procedure used, if you can use buffers. If you need to do this procedure "in
process", you need a way of changing the pH value of at least 2.0 pH – e.g. pH 5.0 and
pH 7.0. You must adapt the corresponding settings in the procedure below and
document that.)
•
Switch off the transmitter Liquiline M CM42. Now all devices (sensor, cable
and transmitter) are switched off.
•
Put the sensor into the buffer with pH 9.0 or pH 9.2.
•
Wait for at least two minutes (to discharge almost all capacities of the
electronic).
•
Switch on the transmitter and wait until the system shows the pH value in the
main screen of the transmitter display. Now (almost) all self tests of the device
have been run successfully.
•
Now run the cable proof test in the menu "SETUP – Functional safety". It must
finish successfully.
•
Set the safety function to SAF1 and set the current output spreading for the pH-
value to 8.0 (minimum) und 10.0 (maximum). All other settings should have
reasonable values.
•
Then switch to SIL mode and then to SIL measuring mode. The system must
run in SIL measuring mode without any errors. Now start to measure both
current outputs.
•
Wait for at least two minutes. The current outputs must show a constant value
between 4 and 20 mA. The value itself is not important, just that it stays
constant and it is not an error current.
Both values of the current outputs are each allowed to spread at a maximum of
±
0.05mA at constant temperature.
•
Now change the buffer and put the sensor into the pH 7.0 buffer. This pH value
is outside the allowed pH interval for SAF1 and therefore the safety function
must execute.
The current outputs must change (because of the pH change) and as soon as the
