118 34410A/11A/L4411A User’s Guide
4 Measurement Tutorial
For ac voltage, additional settling time may be required when the dc level
varies from sample to sample. The default sample delays allow for a dc level
change of 3% of range for all filters. If the dc level change exceeds these levels,
additional settling time is required. The multimeter's dc blocking circuitry has
a settling time constant of 0.2 seconds. This settling time only affects
measurement accuracy when dc offset levels vary from sample to sample. If
maximum measurement speed is desired in a scanning system, you may want
to add an external dc blocking circuit to those channels with significant dc
voltages present. This circuit can be as simple as a resistor and a capacitor.
For ac current, additional settling time is not required when the dc level varies
sample to sample.
Making High–Speed dc and Resistance Measurements
The multimeter incorporates an automatic zero measurement procedure
(autozero) to eliminate internal thermal EMF and bias current errors. Each
measurement actually consists of a measurement of the input terminals
followed by a measurement of the internal offset voltage. The internal offset
voltage error is subtracted from the input for improved accuracy. This
compensates for offset voltage changes due to temperature. For maximum
reading speed, turn autozero off. This will more than double your reading
speeds for dc voltage, resistance, and dc current functions. Autozero does not
apply to other measurement functions.
UG_ED5.book Page 118 Thursday, March 1, 2012 11:28 AM
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