About the input impedance :
The truth are that I got the Fluke 87V
first = Good quality gear ,
and then .. I got the expensive current clamp probe ( AC/DC ) , and even the 40KV HV probe.
As I was and still do , feel some how safe ,
that in such professional equipment, the called impedance compatibility, it is given from the start.
Today, instead of the 87V , I have the 28II , that serves best, my own working style. (out door use )
And it is identical in the electrical specs with the 87V.
After getting the 87V ( and in the six months that I had it ) , I got also three Fluke bench type DMM's,
and the one that I favor most is the 8050A due the high resolution.
I did some measurements today , just to confirm for one more time ,
that my DMM's are spot on.
Picture No 1 :The 8050A is connected with my super accurate resistors decade box with 999K as load,
at the 20MOhm range ..
( I have no idea when ever got calibrated as last time )
Even so , I got an almost spot on reading.
Picture No 2: The 8050A measures now the impedance of the 28II ,
at the same range that it was tested with my decade box.
And the 28II is set to DC mV range , the range that I use with my current clamp probe.
Words looks poor , when the picture speaks by it self.
(8050A 20MOhm + / - 0.25% +3 digits )