Vega D77 Hydrostatic pressure transmitters Bedienungsanleitung PDF herunterladen (Seite 20)

20 Pressure transmitters D76 and D77

Diagnostics

6 Diagnostics

6.1 Maintenance

Pressure transmitters D76 and D77 are main-

tenance-free.

6.2 Failure rectification

Due to continuous self-monitoring, series D70

pressure transmitters offer maximum reliabil-

ity. However, should failures occur, check the

following before removing the pressure

transmitter:

- the atmospheric pressure compensation,

- the electrical connections.

Checking atmospheric pressure com-

pensation

First open the cover of the housing, in which

the atmospheric breather facility is located.

The displayed measured value must not

change. However, if the displayed value

changes, compensation of the atmospheric

pressure is not ensured, which will lead to

distortion of the measured value. Therefore

check:

- the breather facility on the housing

- VEGADIS 12 or VEGABOX 01

- the capillary tubes in the special cable.

Note:

There must always be the same atmospheric

pressure on the breather facility as in the

open vessel.

Voltage

- the terminal voltage on the pressure trans-

mitters must be at least 12 V DC

Current

Current value Condition

3.8 … 20.5 mA standard range for the output

current

0 mA signal cable interrupted

< 3.6 mA sensor electronics or pressure

sensor element defective

22 mA sensor electronics or pressure

sensor element defective

Note for Ex applications

Deviating from above regulation, here termi-

nals 1 and 3 (on VEGADIS 12 terminals 10

and 12) are used only for brief connection to

a certified active, floating measuring instru-

ment (max. value: 470 mW) or an individual

passive, floating ammeter. When connecting,

the regulations for wiring of intrinsically safe

circuits (measuring instrument, supply and

signal circuit) have to be observed.

Checking electrical connections

Pressure transmitter

terminals

~

1 2 3

+

-

Voltage Current

Current

External

energy source

V

mA

mA

1 2 ... 15 16 17 18 19 20 21 22 23 24

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