Measuring Cell Exchange - Siemens Sitrans P DS III PA Serie Servicehandbuch

Service manual
3.3

Measuring cell exchange

CAUTION
Exchanging the measuring cell when voltage is applied is not permitted.
The measuring cell must not be exchanged on the spot.

NOTE
- If necessary the HW version on the license plate must be permanently erased
after having exchanged the connection board and the new HW version labeled
appropriately.
- The housing cover must be closed tight again after having exchanged the con-
nection board.
- After having exchanged the measuring cell, we recommend that you check the
insulation between the short-circuited input terminals and the PE connection.
The insulation resistance should be greater than 10 Mohm.
- If the differential pressure cell is exchanged, the complete measuring cell with
process flange is exchanged.
If you want to exchange the measuring cell in a complete device, you have to pro-
ceed as follows:
1. Turn off the voltage for the device.
2. Remove the cover (1, Figure 4, page 56 and Figure 5, page 56) and the digital
display (3, Figure 4, page 56 and Figure 5, page 56) behind it. In addition to this
you remove both of the screws and take away the conductor band (Figure 7,
page 57).
3. Unscrew the two threaded bolts (4, Figure 4, page 56 and Figure 5, page 56)
holding the electronics in place (5, Figure 4, page 56 and Figure 5, page 56).
4. Remove the electronic case carefully from the housing (Figure 9, page 57). 
Attention: the conductor band of the measuring cell must not be stretched (Figure
12, page 58).
5. Pull off the measuring cell board (6,Figure 4, page 56 and Figure 5, page 56)
which connects the measuring cell (10, Figure 4, page 56 and Figure 5, page 56)
to the electronics with the correct tool e.g. a pair of tweezers (Figure 14, page 59
and Figure 15, page 59).
6. Loosen the locking screw (Figure 28, page 65) which fixes the measuring cell.
7. Unscrew the measuring cell with a suitable fork wrench by approx. two turns 
(Figure 29, page 65). It can then be turned manually. The conductor band must
not be twisted! It must follow every turn of the new measuring cell!
8. Remove residue on the threads of the housing with a non-aggressive cleaning
agent. Carefully push the greased O ring on the thread of the new measuring cell 
(Figure 30, page 66 and Figure 31, page 66) until it is located on the slot provided
for that.
9. Push the measuring cell board through the thread hole (Figure 32, page 66) and
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