Information On The Correct Operation Of Reed Contacts In Bühler Level Switches - Bühler technologies NS 1-G1/2-AM Guía Rápida

NS 1-G1/2-AM
• Disconnect the voltage supply.
• Disconnect the plug.
• Unscrew the plug base. For plug-in connectors with
screw-in plug base, unscrew the top hexagon ring and
pull the complete pin insert up until the bottom of the
base can be unscrewed freely.
• Carefully pull the bent rail with contacts out the top.
NOTICE
The earth wire is a loop and soldered to the protective tube
from the inside in the insertion direction. To prevent breaking
off the earth wire it should not be pulled all the way out.
• Mark the original contact position.
NOTICE
Never attempt to remove the contacts from the front of the
bent rail, as this will damage the glass body. Do not pull on
the cables.
• Carefully slide the contacts to the desired position on the
bent rail. Use a small screwdriver or similar tool to do so.
Use a drop of oil if the contacts are very tight. Please note
the minimum spacing!
If the contacts are configured as NO contact (NO) or NC con-
tact (NC), the contact function can be reversed by turning the
contacts 180°. There is a red mark on the housing indicating
the "NO contact" function. The contact logic assumes the level
switch is installed in an empty tank, i.e. it is only in the operat-
ing position once filled.
Red marking up
NO contact function
with rising level (NO)
• To reverse the switching function, slide the contact out
the top or bottom of the bent rail, turn 180° and slide back
in, and slide into the desired position.
• If the earth wire was pulled out of the protective tube,
first insert this wire into the protective tube.
• Make a loop of the additional cable length and carefully
slide the bent rail back in.
• Screw on the plug base. For plugs with screw-in thread,
attach the plug base clean and screw in hand tight. Leave
the pin insert free so the base can turn around the cables.
Now slide the cables all the way in, lock the pin insert into
the guide and slide all the way in. Tighten the top
hexagon ring hand tight.
4.4 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:
8 Bühler Technologies GmbH
Red marking down
NC contact function
with rising level (NC)
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/Ohm C/µF R/Ohm C/µF
contact V
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!
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.
9
cycles. This is reduces
B
Contact
Load
RC circuit
25 50
R/Ohm C/µF
1 0.1 1 0.47
22 0.022 1 0.1
120 0.0047 22 0.022
470 0.001 120 0.0047
BX200006 ◦ 01/2022