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Gamry is the only supplier of
EIS instrumentation who does NOT specify the maximum frequency as 1
MHz. Gamry's upper limit of frequency is 300 kHz. Why?!
Because we design potentiostats that you can actually use! Gamry
specifies our EIS performance conservatively. We believe that you
should be informed if the impedance error is more than 1% and the phase
error exceeds 2°.
Apparently, other potentiostat manufacturers do not agree. A leading
competitor specifies their EIS maximum frequency as 1 MHz. However,
an examination of the Accuracy Contour Plot below reveals an accuracy
significantly worse than the Gamry PCI4/300.
The news gets worse. At 300 kHz, their error in the impedance
is 7% and the phase error is 8° (assuming a sample impedance of 1 kohm).
When you actually get to 1 MHz, the impedance error exceeds 20% and the
phase error is 25º!
We should point out that Solartron is not the worse offender. At
least they publish their specifications. No other potentiostat
manufacturer other than Gamry can say the same.
These figures were taken from publicly available sources.
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