Agilent Technologies U1251B User's And Service Manual page 137

Performance Tests and Calibration 6
[8] The accuracy does not include the tolerance of the thermocouple probe.
The thermal sensor plugged into the meter should be placed in the operating
enviroment for at least an hour.
Use the Null function to reduce the thermal effect.
[9] Always use relative function to zero the thermal effect with open test lead
before measuring the signal.
If you do not use Relation function, add 20 digits for accuracy purposes.
[10] 10A continuous, and additional 0.5% to specified accuracy when measuring
a signal greater than 10 A~20 A for 30 seconds maximum.
After measured current for > 10 A, to cool down the meter for twice the
measuring time you applied before low current measurement.
[11] The current can be measuring from 2.5A to 10A continuous, and the
additional of 0.5% to specified accuracy as measure the signal greater than
10A~20A for 30 seconds maximum.
After measured current for > 10A, to cool down the meter for 2 times of
measuring time you applied before low current measurement
[12] For signal frequency greater than 1 kHz, additional 0.1% per kHz to be
added to accuracy
Agilent U1251B/U1252B User's and Service Guide 123