User`s guide

53220A/53230A User’s Guide 123
53220A/53230A Input Signal Conditioning 4
Input Protection
The maximum input voltage (including any DC offset) allowed with 50Ω input
impedance is ±
5.125 Vp. If the input voltage exceeds
~
± 10.0 Vp, the input
protection relay opens - changing the input impedance to 1 M
Ω.. (The display
and Impedance softkey will still indicate a 50
Ω setting however.)
With the relay open, the corresponding channel key flashes until the input
voltage is removed or reduced below the damage threshold and the key is
pressed. This sets the impedance back to 50
Ω.
To programmatically determine if the protection relay has been opened, the
command:
INPut[{1|2}]:PROTection?
queries the relay state (0 = relay closed, 1 = relay open). With the input volt-
age removed or reduced below the damage threshold, the protection relay is
reset (closed) with the command:
INPut[{1|2}]:PROTection:CLEar
setting the input impedance back to 50
Ω.
Voltage Overload Bit The opening of the input protection relay corresponds to
the ‘Voltage Overload’ bit (bit 0) being set in the counter’s Questionable Condi-
tion and Questionable Event registers. The bit in the Condition register is
cleared by the INPut:PROTection:CLEar command or by changing the
input impedance to 1 M
Ω. The bit in the Event register is cleared by reading
the register. See Chapter 8 - Status Conditions for more information.