Reference 3000 Specifications
89
with a 50
output impedance and measuring the error as a function of frequency. Resistance in
either input causes a loss of CMRR.
9)
Voltage measurement is actually performed with a
3 V signal input to the ADC signal chain. A
4
attenuator divides down higher-voltage electrometer outputs, so they fit into a
3 V input, thus making
a
12 V full-scale range. Gains of 10 and 100 are available to generate 300 mV and 30 mV ranges.
10)
The total error in a voltage measurement is:
Error = Zero Offset Error + Gain Error × Voltage
For a 1 V signal, the error can be as high as 3 mV.
11)
There are 11 hardware current ranges, separated in sensitivity by decades. The ranges are: 300 pA, 3
nA, … 300 mA, 3 A full scale. The ×10 and ×100 gains add two virtual ranges of 30 pA and 6 pA full
scale.
12)
The voltage across the current-measurement resistor, Rm, is as shown. Slightly higher voltages may be
seen at the working-electrode terminal on the cell cable because the cable has both resistive and
inductive impedance.
13)
The total error in a current measurement is:
Error = Input Current Range Zero Offset × FS C Gain Tolerance × Measured Current
For small currents (pA) the first term is usually dominant.
For large currents (µA), the first term can usually be ignored.
The units for the error are amperes.
14)
Drift can be approximated by simple drift in the Range Zero Error. In reality all three terms in the
equation above can have drift.
15)
The Current-to-Voltage converter bandwidth is a function of the current range, the cell cable, and the
IEStability setting. The bandwidth can be very low on very sensitive ranges. Longer cell cables add
capacitance and slow the current measurement.
16)
The total error in a voltage setting is:
Error = DC Zero Gain × Voltage Setting
For a 1 V signal, the error can be as high as 3 mV.
17)
This specification is guaranteed by design. It is not tested.
18)
This specification is measured by applying zero voltage across a 1
resistor and measuring current
noise on the 30
A scale. 1
V of voltage noise will create a current of 1
A. The filters in the ADC
Chain for the I Signal are used to limit the bandwidths as shown in the spec. Signal averaging via
Gamry’s DSP mode further reduces the measured noise.
19)
See Appendix D.
20)
Isolation quality has both DC factors and AC factors (predominately at the 300 kHz power-supply
frequency). Only the DC leakage current is shown here. Consult Gamry’s technical support for
additional information.
21)
Excluding external power adapter and any cables supplied with unit.
22)
Excluding removable line cord.
