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Overload Indicator
An indication will appear in the oscilloscope message bar when the differential or common
mode voltages are beyond the operating ranges of the probe. Note that the warning
message below may trigger before any saturation occurs. It is designed to guarantee that
the system will not fail to indicate an overload.
3102A
3206A
3220
3605A
Auto Zero
Auto Zero corrects for DC offset drifts that naturally occur from thermal effects in the
differential amplifier. For example, the DC offset drift of the HVD310xA probes is 70 μV/°C
(worst case) referred to the output. If the probe is set to 50x attenuation and the ambient
temperature changes by 10 °C, the DC offset drift could be as high as (70 μV/°C)(50)(10 °C)
= 35 mV referred to the probe tip. If the signal was 1400 Vp-p in 500x attenuation mode,
the DC offset drift at same ambient temperature could be as high as (70 μV/°C)(500)(10°C)
= 350 mV due to the probe tip (although any offset accuracy error from the oscilloscope
itself would likely dominate the measurement).
Auto Zero is disabled when AC coupling is selected.
Auto Zero is invoked manually from the Probe dialog that appears behind the Cn setup
dialog when the probe is connected to the oscilloscope.
Note: HVD3xxxA probes may remain connected during Auto Zero. HVD3220 probes should
be disconnected.
Always perform Auto Zero after the probe has warmed up at least 20 min. If the probe is
disconnected then re-connected, repeat Auto Zero. Depending on the accuracy desired
and/or changes in the ambient temperature, it may be necessary to Auto Zero more often.
Overload Indicator Thresholds
X1000 Attenuation
Differential Mode: ± 1.78 kV
Common Mode: ± 1.78 kV
X500 Attenuation
Differential Mode: ± 2.1 kV
Common Mode: ± 2.1 kV
Any Attenuation
Differential Mode: ± 2.1 kV
Common Mode: ± 2.1 kV
X2000 Attenuation
Differential Mode: ± 7.7 kV
Common Mode: ± 7.7 kV
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Operator's Manual
X100 Attenuation
Differential Mode: ± 158 V
Common Mode: ± 1.8k V
X50 Attenuation
Differential Mode: ± 180 V
Common Mode: ± 2.1 kV
X200 Attenuation
Differential Mode: ± 760 V
Common Mode: ± 7.7 kV
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