SC5 Signal Conversion Performance Measurements
60
Accuracy
The accuracy of the analog outputs can be deduced from the offset and gain error measurements. The result for
uncalibrated and calibrated outputs is summarized below:
Calibrated Accuracy error Abs. Accuracy at 0 V Abs. accuracy at ±10 V
No < ± 0.85‰ of setting ±550 µV < ±550 µV < ±8.5 mV
Yes < ± 0.72‰ of setting ±25 µV < ± 25 µV < ±7.2 mV
Table 16: Accuracy of the analog outputs.
Resolution
The SC5 achieves a resolution of 22-bit by using the hrDAC™ algorithm, 2 bits more than the native resolution. The
following measurement shows a comparison between 20- and 22-bit operation. The measurement was done with
AO1 connected to a National Instruments 4071 PXI digital multimeter operated in digitizer mode (6.5 digits) at 100
S/s. The following settings have been used for the measurement:
DMM
Measured output: AO1 Mode of operation: Digitizer, DC Volts
Output amplitude: 250 µV to 2.25 mV Range: 100 mV
Resolution: 26 bit
Sample rate: 100 S/s
Figure 40: Voltage sweep of 2 mV with hrDAC off (20-bit resolution, upper curve) and hrDAC on (22-bit resolution, lower
curve). The curves have been offset for clarity. The inset shows a 100 µV region of the 22-bit measurement, making the
single 22-bit LSB steps visible.
Output voltage [mV]
2.5
2.0
1.5
1.0
0.5
0
0 2 4 6 8 10 12 14 16 18 20 22
Time [s]
hrDAC™ OFF (20-bit)
hrDAC™ ON (22-bit)
Output (+1 mV) [μV]
140
120
100
80
60
40
20
0
0 0.2 0.4 0.6 0.8 1.0
Time [s]
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