Measurement Resolution and Accuracy

Frequency accuracy, as opposed to resolution, depends on the stability of the on-board frequency reference, which is usually a crystal oscillator, and these are usually stable to lOppm if the temperature is held stable. For more precise applications, some instruments allow a very accurate external frequency reference to be used. 

Impedance measurement accuracy depends on the measurement of ac voltage and current through the cell. The 4-terminal technique is extremely important for measurement of low impedance devices as explained earlier. Other considerations are the voltage and current ranges that are available in the potentiostat and HiA, the bandwidth of the potentiostat (this is dependent on the range selection), and the measurement accuracy of the frequency response analyzer. 

Usually, measurement of ac voltage is not so much of a problem and bandwidths of 1 MHz and beyond can fairly easily be achieved with careful design. Current measurement, however, usually presents much more of a problan. It is therefore extremely important to check the specified bandwidth of the potentiostat for the particular measurement that is required. The bandwidth of any potentiostat will tend 

It is not sufficient to only consider the bandwidth of the electrometer (the voltage measurement circuits) the whole system, especially including the bandwidth of ihe current measurement system, should be considered for the specific cells that are likely to be tested. Wherever possible, the instruments should be tested on the actual cells to be analyzed to make sure that they are able to make the required measurements. 

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