Problem in measuring potential because of oscilloscope's input impedance
Use a unity gain opamp that has the bandwidth
Maybe use an opamp as a buffer, the opamp will need to have more bandwidth than the sensor (and will add in an voltage offset error Vos, so select an opamp with a low voltage offset). The opamp will also need to be able to source more than ~8mA on the output.
Another option would be to use an opamp with gain.
You might also want to know that there are many eval boards such as this to make adding an opamp for test easier. Almost all manufacturers provide eval boards for opamps also.



simulate this circuit &ndash; Schematic created using CircuitLab