Specifying Resolution - Agilent Technologies 3458A User Manual

Specifying
Resolution
1. You can also specify resolution using the RES command. Refer to the RES command in chapter 6 for
examnples showing its usage.
68 Chapter 3 Configuring for Measurements
if you specify 60 PLCs of integration time, the multimeter averages six 10
PLC readings.
Typically, you should select the integration time that provides adequate speed
while maintaining an acceptable amount of accuracy and resolution. Table
18 shows the relationships between integration time and digits of resolution
for analog AC measurements.
Table 18: Analog AC A/D Converter Relationships
Digits of
Resolution
4.5
5.5
6.5
You can specify the measurement resolution as the last parameter
(%_resolution parameter) of a function command (FUNC,ACV, ACI, etc.)
or the RANGE command.
For all analog AC voltage and current measurements %_resolution is
specified as a percentage of the command's max._input parameter. The
multimeter multiplies the specified %_resolution parameter times the
max._input parameter to determine the measurement resolution. To
determine the value of the %_resolution parameter, use the equation:
%_ resolution = (actual resolution/maximum input)
For example, suppose your maximum expected input is 10 VAC and you
need 1 mVAC of resolution. The equation evaluates to:
%_ resolution = (0.001/10)
For analog AC measurements, resolution is determined by the A/D
converter's integration time. When you specify a resolution, you are actually
indirectly specifying an integration time. Since the NPLC command can also
specify an integration time, an interaction occurs when you specify resolution
as follows:
•
If you send the NPLC command before specifying resolution, the
multimeter satisfies the command that specifies greater resolution (more
integration time).
•
If you send the NPLC command after specifying resolution, the multimeter
uses the integration time specified by the NPLC command, and the
previously specified resolution is ignored.
Power Line Cycles (NPLC command)
LFREQ = 6OHz
0 – .000030 0 – .000025
.000036 – .000360 .000030 – .000300
.000366 – 1000 .000305 – 1000
1
×
100 = 0.01
LFREQ = 5OHz
×
100