WIKA TR10-A - Handbuch (Seite 35)

WIKA operating instructions RTD and TC, intrinsically safe designs (Ex i)
3345267.12 01/2014 GB/D
35
GB
Simplified verification of intrinsic safety for the above-mentioned combination
Measuring insert Zener barrier Z954 Display instrument
(non-hazardous area)
U
i
: DC 30 V U
o
: DC 9 V Um: AC 250 V Uo: AC 230 V
I
i
: 550 mA I
o
: 510 mA I
i
: nA Io: nA
P
i
(max) at the sensor: 1.5 W P
o
: 1150 mW P
i
: nA Po: nA
C
i
: negligible C
o
: 4.9 µF C
i
: nA Co: nA
L
i
: negligible L
o
: 0.12 mH L
i
: nA Lo: nA
Upon comparing the values, it is obvious that it is permissible to connect these units to one
another. However, the operator must also take into account the values for inductance and
capacitance of the electrical connection leads.
These calculations apply to the Z954 Zener barrier in connection with a resistance thermometer
Pt100 in 3-channel mode without grounding, i.e., symmetrical operation of the resistance
thermometer in 3-wire circuit on a display or evaluation instrument.
Electrical connection
For sensor connections, terminal, cable or connector assignments, see chapter
6.1 “Electrical connection”.
10. Maintenance and cleaning
10.1 Maintenance
These thermometers are maintenance-free.
Repairs must only be carried out by the manufacturer.
10.2 Cleaning
CAUTION!
■ Clean the instrument with a moist cloth. This applies in particular to thermometers
with a housing made of plastic and cable probes with plastic-insulated connection
lead, to ensure that any risk of electrostatic discharge is avoided.
■ Electrical connections must not come into contact with moisture.
■ Wash or clean the dismounted instrument before returning it, in order to protect
staff and the environment from exposure to residual media.
■ Residual media in dismounted instruments can result in a risk to persons, the
environment and equipment. Take sufficient precautionary measures.
For information on returning the instrument, see chapter 12.2 “Returns”.
9. Calculation examples for ... / 10. Maintenance and cleaning