General Information - Agilent Technologies 3458A Calibration Manual

4 / AC Voltage

General Information

The 3458A supports three techniques for measuring true rms AC voltage, each offering unique capabilities.
The desired measurement technique is selected through the SETACV command. The ACV functions will then
apply the chosen method for subsequent measurements.
The following section provides a brief description of the three operation modes along with a summary table
helpful in choosing the technique best suited to your specific measurement need.
SETACV SYNC Synchronously Sub-sampled Computed true rms technique.
This technique provides excellent linearity and the most accurate measurement results.
It does require that the input signal be repetitive (not random noise, for example). The
bandwidth in this mode is from 1 Hz to 10 MHz.
SETACV ANA
Analog Computing true rms conversion technique.
This is the measurement technique at power-up or following an instrument reset. This
mode works well with any signal within its 10 Hz to 2 MHz bandwidth and provides the
fastest measurement speeds.
SETACV RNDM
Random Sampled Computed true rms technique.
This technique again provides excellent linearity; however, the overall accuracy is the
lowest of the three modes. It does not require a repetitive input signal and is, therefore,
well suited to wideband noise measurements. The bandwidth in this mode is from 20
HZ to 10 MHZ.
Selection Table
Technique Frequency Range
Synchronous Sub- 1 Hz –10 MHz
sampled
Analog 10 Hz – 2 MHz
Random Sampled 20 Hz – 10 MHz
Synchronous Sub-sampled Mode (ACV Function, SETACV SYNC)
Range Full Scale Maximum
Resolution
10 mV 12.00000 10 nV
100 mV 120.00000 10 nV
1 V 1.2000000 100 nV
10 V 12.000000 1 µV
100 V 120.00000 10 µV
1000 V 700.0000 100 µV
2
AC Accuracy
24 Hour to 2 Year (% of Reading + % of Range)
3
1 Hz to
Range
40 Hz
10 mV 0.03 + 0.03
100 mV–10 V 0.007 + 0.004 0.007 + 0.002 0.014 + 0.002 0.03 + 0.002
100 V 0.02 + 0.004
1000 V 0.04 + 0.004
86 Appendix A Specifications
Best
Accuracy
0.010%
0.03%
0.1%
Input Impedance
1 MW±15% with<140pF 0.003 + 0.02
1 MW±15% with<140pF 0.0025 + 0.0001
1 MW±15% with <140pF 0.0025 + 0.0001
1 MW±2% with <140pF 0.0025 + 0.0001
1 MW±2% with <140pF 0.0025 + 0.0001
1 MW±2% with <140pF 0.0025 + 0.0001
3 3
40 Hz to 1 kHz to
1 kHz 20 kHz
0.02 + 0.011 0.03 + 0.011
0.02 + 0.002 0.02 + 0.002
0.04 + 0.002 0.06 + 0.002
Repetitive Readings /Sec
Signal Required Minimum Maximum
Yes 0.025
No 0.8
No 0.025
Temperature Coefficient
(% of Reading +% of Range) /°C
2
ACBAND £ 2 MHz
3
50 kHz to
20 kHz to
100 kHz
50 kHz
0.1 + 0.011 0.5 + 0.011
0.08 + 0.002
0.035 + 0.002 0.12 + 0.002
0.12 + 0.002 0.3 + 0.002
1. Additional error beyond ±1°C,
but within + 5°C of last ACAL.
For ACBAND > 2 MHz, use
10
10 mV range temperature
coefficient for all ranges.
50
2. Specifications apply full scale
45
to 10% of full scale, DC
< 10% of AC, sine wave input,
crest factor = 1.4, and
1
PRESET. Within 24 hours and
±1°C of last ACAL. Lo to
Guard Switch on.
Peak (AC + DC) input limited
to 5 x full scale for all ranges in
ACV function.
Add 2 ppm of reading
additional error for Agilent
factory traceability of 10 V DC
to US NIST.
3. LFILTER ON recommended.
100 kHz to 300 kHz to
300 kHz 1 MHz
4.0 + 0.02
0.3 + 0.01 1 + 0.01
0.4 + 0.01 1.5 + 0.01
1 MHz to
2 MHz
1.5 + 0.01