Information On The Correct Operation Of Reed Contacts In Bühler Level Switches; Electrical Voltage - Bühler technologies NS OM-6 Serie Guía Rápida

NS OM-6x
Please refer to the compatibility charts in the appendix for the
pin assignment and the electrical data. Proceed as follows: For
NS OM-61 or NS OM-64, select (per your order) the plug type,
contact type and the number of contacts. For NS OM 63-KN
(continuous level measurement 4-20 mA), select the pin as-
signment for the M3 or M12 plug.
For version NS OM-VA-MKS, the contacts are included as a sep-
arate line item. The MKS contacts are installed by the cus-
tomer.
The technical data for the individual NC and NO contacts,
please see the end of these instructions.
4.3 Information on the correct operation of reed
contacts in Bühler level switches
Based on their construction, reed contacts are very long last-
ing and reliable components. Yet the following should be con-
sidered when using them:
Life of reed switches
The life of reed switches can be up to 10
by high stress and / or incorrect or the absence of protective
circuits when switching inductive, capacitive or lamp loads.
It's therefore important to ensure NEVER to exceed one or sev-
eral of the maximum approved limits, even temporarily, and
to install a contact protective circuit for loads which are not
purely ohmic. Using test lamps when installing the devices is
also prohibited, as these can temporarily allow too much cur-
rent to flow, which can damage the reed contacts. In this case
non-volatile testing equipment should always be used.
Contact protective circuits for reed switches
For direct current voltage a recovery diode per figure A must
be connected parallel to the contact.
For alternating current voltage an RC circuit per Figure B and
Table 1 must be connected parallel to the contact.
A
Contact
Load
Recovery diode
Load in VA 10
Voltage at R/ C/µF
contact V Ohm
24 22 0.022
60 120 0.0047
110 470 0.001
230 470 0.001
Please note the max. voltage/load ratings of the respective
level contacts!
BX100010 ◦ 03/2021
9
cycles. This is reduces
B
Contact
Load
RC circuit
25 50
R/ C/µF R/ C/µF
Ohm Ohm
1 0.1 1 0.47
22 0.022 1 0.1
120 0.0047 22 0.022
470 0.001 120 0.0047
Voltages and currents
All Bühler level contacts with reed switch can switch minimal
Switching voltages of 10 µV and minimal switching currents
of 1 µA.
The maximum values specified for the respective contact
types apply.
Level contact with reed switches can therefore be used for SPS
applications as well as for high loads (within the maximum
limits) without hesitation.
Contact material
All reed switches in Bühler level contacts use rhodium as the
contact material for the actual contact areas.
Magnetic fields
Avoid external magnetic fields, including from electric mo-
tors. These can interfere with the function of the reed
switches.
Mechanical loads
Do not expose the level switch to strong blows or bending.
4.4 Adjusting contacts after the fact
NOTICE
Some level switches also have electronic assemblies on the
perforated rail depending on the model. These are positioned
so they do not limit the setting range of the contacts. Please
take appropriate measures so as not to damage the electronic
assemblies when installing and removing the contacts. Model
in the 63-KN and NS OM-VA-K series supply a continuous
4-20 mA analogue signal (normally: 4 mA lowest point, 20 mA
highest point). These devices require no configuration.
DANGER

Electrical voltage

Electrocution hazard.
a) Disconnect the device from power supply.
b) Make sure that the equipment cannot be reconnected to
mains unintentionally.
c) The device must be opened by trained staff only.
d) Regard correct mains voltage.
WARNING
Fluids or gasses discharged at high pressure harmful to
the environment or health
a) Depressurise the system/component prior to installation.
b) Drain the system/component in accordance with envir-
onmental regulations. Wear suitable protective clothing.
Bühler Technologies GmbH 9