Teledyne HVD3102 Operator's Manual page 23

Operator's Manual
Probe Offset
The offset range of the probe allows you to remove a DC bias voltage from the differential input
signal while maintaining DC coupling. This ensures that the probe will never be overdriven while
a signal is displayed on screen. In addition, it will prevent the oscilloscope from being overdriven
and getting inaccurate measurements.
The total usable offset of the oscilloscope and probe system is a function of the oscilloscope
V/div setting, oscilloscope offset at that V/div setting, probe attenuation, and probe offset at that
attenuation setting, and this total maximum offset may be calculated.
First, it is necessary to know the oscilloscope front end V/div setting with the probe connected.
This may be calculated as follows:
Oscilloscope Front End V/Div = (Probe and Oscilloscope) V/Div ÷ Probe_Attenuation
Once the Oscilloscope Front End V/div value is known, then it is possible to know the maximum
offset available in the oscilloscope at this V/div setting either by referencing the oscilloscope
specifications or setting the maximum offset value on the oscilloscope for that V/div setting.
Then, the maximum offset available with the probe and oscilloscope combination can be
calculated as follows:
Max Positive Offset Available
Max Positive Offset (Probe and Oscilloscope together) =
Oscilloscope Positive Offset (at Oscilloscope Front End V/div) * Probe Attenuation – 10V
Max Negative Offset Available
Max Negative Offset (Probe and Oscilloscope together) =
Oscilloscope Negative Offset (at Oscilloscope Front End V/div) * Probe Attenuation + 10V
In both cases, the maximum offset available cannot exceed the HVD3102 maximum offsets of
±150V at 100x attenuation and ±1500V at 1000x attenuation or the HVD3106 maximum offsets
of ±150V at 50x attenuation and ±1500V at 500x attenuation.
NOTE: The offset values reported in the oscilloscope's channel descriptor box may deviate
slightly from expected values, based on calculations per the formulas above. The reported
probe attenuation is a "nominal" value and can deviate slightly from the actual value measured
during calibration and stored with the probe. The actual offset value reported uses the actual "as
measured" probe attenuation value. This provides for higher DC and low frequency gain
accuracy than would otherwise be possible.
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