Chrono Amperometry with RCB200 (position A) – Resolution and accuracy

Files:
RCB200-A .EXP
RCB200-A 014.CRV

Abstract

A Chrono Amperometry is used to establish that the resolution and the accuracy of the measurements are operated within specifications. The experiment uses the 10 µA range.

RCB200 with WORK connected to position A and functional ground connected to the potentiostat rear panel.

The experiment imposes +800 mV during 30 seconds then -800mV during 30 seconds. Acquisitions are made every 0.04 sec.

Display: Type = Normal X = Time Y1 = Current Y2 = No

1) Accuracy
The mean value equals 8006 nA, the maximum value is inferior to 8018 nA and the minimum value is superior to 7995 nA.
The expected value is 8000 nA ± 28 nA. These 28 nA are calculated from the specifications of the resistor and from the specifications of the instrument. The resistor mounted in the RCB200 box has the following specifications: 100 KOhms ±0.1%. The accuracy with the potentiostat is 0.2% of the range. Thus 0.2% of 10 µA + 0.1% of 800mV/100kOhms = 28 nA.

2) Resolution
The specification is 0.003% of the range. With the 10 µA range it corresponds to 0.003% = 0.3nA. This resolution corresponds to the smallest distance between experimental points.
A simple way to evaluate the quality of the measurement is to operate a linear regression on the whole experiment.

Linear regression----------------------- 16-09-1999, 14:17:18
X min.: 0.04
X max.: 29.96
Mode: y=f(x)
Result: y(µA/cm²) = 0x(sec.) + 8.006
x(y=0) = 506823
Coefficient: 0.00137426

Since the correlation coefficient is very small, the mean value is close to the constant term. The fact that the correlation coefficient is very low indicates that the current is not time dependent. In this case it demonstrates that there is no drift on the measurements which is to say that the measurements are correct.

If your results give a current equals to 8000 nA ± 28 nA on the range 10 µA, it demonstrates that your apparatus is better than the specifications. If not, the error on Vg must be taken into account to draw any conclusion. This error is equal to 0.5 %.

You can evaluate the performances regarding the resolution and the accuracy with the other ranges using the same principle.