Multichannel Systems nanoZ manual - Manual (Page 10)

nanoZ User Manual
6
The nanoZʼs electroplating circuit has a native resolution of ~100nA. To enable smaller
currents and the ~1nA electroplating accuracy offered by the nanoZ (software v1.4.0 or
later), devices shipped prior to April 2012 need to be recalibrated (see Appendix E).
The calibration adaptor should be orientated with the ʻNZ-CALʼ text closest to the
USB port, and the software should be set to No Adapter / Probe not selected.
Tips
for
accurate
Z
measurements
The nanoZ is capable of providing very accurate measurements across a wide
range of test frequencies and impedances (Appendix B). Nonetheless, care
should be taken to protect the test setup from electromagnetic interference (EMI)
such as 50/60Hz power line interference. The nanoZ is susceptible to EMI
because it uses very small test signals for measuring impedance. To ensure
accurate results, periodically check the signal quality using the Scope display of
the nanoZ application (or the signal buffers if using the Matlab SDK). Moderate
levels of power line noise or band-limited noise outside the impedance test
frequency of interest are not a problem. However, if the test signal is excessively
noisy and the amplifier is saturated (i.e. the cyan trace on the scope is either not
visible or appears ʻclippedʼ), then the measured impedance will not be accurate.
The nanoZ software will report if any part of the test signal is clipped, and
highlight in yellow the affected channels in the Report window.
If necessary, enclose the setup in wire mesh or aluminum foil to shield it from
EMI, and be sure to connect the shield to the reference wire. Move the setup
away from common sources of 50Hz noise, in particular fluorescent table lamps,
electric motors, or other lab equipment. In especially noisy environments it may
also help to run the nanoZ on a battery-powered laptop.
Clipping of the test sinusoid may also occur immediately after switching
channels, or if an impedance measurement is made immediately after applying
an electroplating current, before charge on the electrode site has had sufficient
time to dissipate. In both cases the nanoZ will report an artifactually low post-
plating impedance and a warning message, and attempt to re-test the electrode
several times before proceeding to the next channel. Refer to the subsequent
sections describing the various automated modes of operation for how to avoid
this artifact if and when it arises.
clean test signal test signal clipped warning in meter display