Keysight 34972A - Snubber Circuits; RC Protection Networks

7Tutorial
322 Keysight 34970A/34972A User’s Guide
Snubber Circuits
Whenever a relay contact opens or closes, electrical breakdown or arching can
occur between the contacts. This can cause high-frequency noise radiation,
voltage and current surges, and physical damage to the relay contacts.
A breadboard area is provided on the 34903A to implement custom circuitry such
as simple filters, snubbers, and voltage dividers. The breadboard area provides
the space necessary to insert your own components but there are no circuit board
traces here. You can build these networks to provide contact protection when
actuating AC power line for reactive loads. Although many types of contact
protection networks can be used, only RC networks and varistors are described in
this section.
RC Protection Networks
When designing RC protection networks, the protection resistor R
p
is selected as
a compromise between two resistance values. The minimum value of R
p
is
determined by the maximum acceptable relay contact current (I
max
). For the
34903A, the maximum allowable relay current (I
max
) is 1A DC or AC rms. Thus, the
minimum value for R
p
is V/I
o
, where V is the peak value of the supply voltage.
Relay
Contact
C
p
R
p
Varistor
I
L
R
L
R
p
V
I
max
--------
V
2
--==