High Voltage input ans external attenuator

[Christian]

Hi,

Here is my thread about the input impedance of the QA402/403. Hopefully there is some useful info. I’m also constructing a precision input attenuator (0dB/-6dB/-10dB). At the -10dB setting it can accept 177VDC or 250Vac on the input without overloading the QA403 inputs.

QA403 real input impendace?

Ok, so after digging deeper into available precision (0.1%) resistors I cooked up the following, even simpler solution: [Capture] This design slightly increases (from the previous solution) the resistances for the 6dB and 10dB attenuation settings, but simultaneously reduces the power dissipation in the divider resistors. Now 0.5W versions can be used (<250mW max dissipation). And only two resistor values are required The parts list is in the schematic. I will post pics of my …

Cheers,

Christian