Siemens SITRANS P 7MF4232, Руководство по эксплуатации

Страница: 31 / 38

7MF4232 Operating Instructions
29 C79000-B5676-C92-01
- When trying to decrease the value using the key, the error note is displayed additionally to the
(not changeable) value
(Explanation: If the start of scale is changed the measuring span remains unchanged. The full scale
300 mbar violates the measuring range limits.)
- Press -and keys together for about 2 s, full scale is set to 250.00 mbar.
- Use the key to set the full scale to 240.00 mbar.
4.3.3.3 Correction of zero point
If the transmitter is installed and operational, external influences such as angle of installation, ambient
temperature, or installation dependent pressure effects (e.g. head of liquid in the impulse pipe line to the
transmitter) may cause an offset in the transmitter’s zero point. This offset (max. 20 % of the max. measur-
ing span) can be corrected in the SITRANS P transmitter without modifying the start of scale and full scale
settings in modes 5 and 6 (correction of zero point).
- Evacuate (<0.01 % of measuring span)
- Select mode 7 using the
M
key.
- Press the and keys simultaneously for about 2 s.
The value 0 or 0.0 etc. to 0.0000 is displayed on the LCD, depending on the maximum measuring span
of the transmitter and the selected engineering unit.
.
Note
At absolute pressure sensors the start of scale is at vacuum. The zero adjustment in ventilated
transmitters leads to misadjustments! The factory calibration function (accessable only by
HART
R
command) will undo misadjustments if neccessary.
Example
A transmitter with a maximum measuring span of 1.3 bar is calibrated for a measuring range of 200 to
800 mbar (4 to 20 mA), i.e. start of scale 200 (mbar) in mode 5, full scale 800 (mbar) in mode 6 and engi-
neering unit ”mbar” in mode 14. The transmitter is, however, being used in hotter conditions, which is
causing an offset (200.3 mbar) in the original zero point.
This offset is to be corrected.
- Evacuate (<0.01 % of measuring span)
- Press the and keys simultaneously for about 2 s in mode 7, the value of ”0.0 mbar” is displayed
- Apply the original absolute pressure; ”200.0 mbar” is displayed
The start of scale and full scale of 200 (mbar) and 800 (mbar) set in modes 5 and 6 respectively remain
unchanged.