White Matter NanoZ Manuale Utente Scaricare il pdf (Pagina 10)

nanoZ User Manual

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.

Finally, we recommend that the electrode and reference connections are kept as

short as possible. Long wires may distort results due to their capacitance. Avoid

open ends which act as antennas.

clean test signal test signal clipped warning in DMM display

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White Matter NanoZ Manuale Utente Pagina 10