Gn610 And Gn611 Input Overload Protection; Gn610, Gn611 Protection Mechanisms; Overvoltage And Current Protection - HBM Genesis series Technical Note

6 GN610, GN611 Protection mechanisms

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GN610, GN611 Isolation and type testing
6.1 Overview

Overvoltage and current protection

All signal inputs are protected against voltage overload. This is specified at
± 1000 V for all ranges except for the ± 1000 V range that is limited to
± 1250 V. Exceeding these limits can damage the input card.

GN610 and GN611 input overload protection

The input section has several methods to protect against voltage overload on
the input.
Every selected input range allows a 200 % overload without any change of input
resistance or auto ranging. This 200 % overrange is designed to allow for
smaller voltage overloads without effecting the measurement. Within this
200 % overload the amplifier is also able to respond with normal rise/fall times
to signal being restored within the standard selected range.
When exceeding the 200 % overload condition, the input impedance might start
to increase. The impedance increase will lower the input current with the
positive effect of lowering the dissipated heat. It is the excessive heat
dissipation that typically damages the input channel.
The first action of the system will be to add an additional current load on the
input signal to create an extra voltage drop on the input series resistance. The
actual additional current depends on several factors and is therefore not
predictable. A negative side effect of this additional current is the extra power
dissipated in the input section which in turn results in additional heat dissipation.
Secondly, within the lower ranges of the amplifier (≤ ± 5 V ranges) the input
section will start switching to disconnect from the input signal to reduce the
power dissipated.
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