Model 6517B Electrometer Reference Manual
Section 5: Measurement options
6517B-901-01 Rev. C / August 2015
5-19
Zero check, relative, and zero correct
Zero check
When zero check is enabled (on), the input amplifier is reconfigured to shunt the input signal to low as
shown in the figure below. When you enable or disable zero check, that state is assumed regardless
of which function you select. In other words, you cannot set a unique zero check state (on or off) for
each function.
Zero check is enabled by pressing the Z-CHK key. When enabled, the "Zerocheck" message is
displayed. Pressing Z-CHK a second time disables zero check. To ensure proper operation, always
enable zero check before changing functions (V, I, R, or Q).
In coulombs, enabling zero check dissipates the charge. That is, the charge reading is reset to zero.
When zero check is disabled, a sudden change in the charge reading (zero check hop) occurs. This
effect can be cancelled by enabling REL immediately after zero check is disabled.
For voltage, current and resistance measurements, leave zero check enabled when connecting or
disconnecting input signals. For charge measurements, disable zero check before connecting the
input signal. If zero check is left enabled when you connect the input signal, the charge dissipates
through the 10 M
Ω
resistor (see figure below).
Figure 66: Equivalent input impedance with zero check enabled
