Teledyne HVD3102 Operator's Manual page 24

HVD3102 and HVD3106 High-Voltage Differential Probes
Bandwidth Limiting
To comply with various test standards used for quantifying output noise of power supplies, the
probe is capable of switching the bandwidth limit from Off (maximum bandwidth) to 20 MHz in
the channel Vertical Adjust dialog.
Auto Zero
Auto Zero corrects for DC offset drifts that naturally occur from thermal effects in the amplifier.
The probe incorporates Auto Zero capability to remove the DC offset from the probe's differential
amplifier output to improve the measurement accuracy. Auto Zero is invoked manually from the
Probe dialog that appears behind the Channel setup dialog when the probe is connected to the
oscilloscope.
NOTE: Remove the probe from the test circuit before performing Auto Zero.
Always perform Auto Zero after probe warm-up (recommended warm-up time is 20 minutes).
Depending on the measurement accuracy desired and/or the change in the ambient
temperature where the probe is located, it may be necessary to perform Auto Zero more often. If
the probe is disconnected from the oscilloscope and re-connected, repeat Auto Zero after a
suitable warm-up time.
For example, the DC offset drift of the probe 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, then the DC offset
drive could be as high as (70 μV/°C)(50)(10°C) = 35mV (referenced to the probe tip). If the probe
is being used to measure a 3Vp-p signal, then the DC offset drift in this case could be a little
more than 1%. If the signal measured was 1400Vp-p in 500x attenuation mode, then the DC
offset (in the same ambient temperature condition) could be as high as (70 μV/°C)(500)(10°C) =
350 mV due to the probe tip, but any offset accuracy error from the oscilloscope itself would
likely dominate the measurement.
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