Fluke 80k40 schematic

Bandwidth Measurement

Fluke 80K40 HV Probe

Introduction

This is the results of a test to determine the bandwidth of a Fluke 80K40 HV Probe.

Test 1

The Probe was connected to a Fluke 87 III meter. A Fluke 5101B calibrator was used as
the signal source.

Frequency Meter reading mV Comments

DC 100.1
50Hz 100.5
60Hz 100 Unstable reading

100Hz 98.6
200Hz 90.6
400Hz 68.7
800Hz 35.8

1KHz 28.0

100KHz 7.3

Test Method 2

A HP3585A spectrum analyzer was used.

This Spectrum analyzer has a built in tracking generator.

A ‘scope probe was added to the 1M input to provide a 10M input for the Fluke HV
probe.

The ‘scope probe was measured to provide a –14db signal.

REF -13.6 DBM MARKER 233.0 HZ
10 DB/DIV RANGE -10.0 DBM -74.0 DBM

START .0 HZ STOP 1 000.0 HZ

RBW 10 HZ VBW 30 HZ ST 20.0 SEC

The Marker shows the signal at 223Hz to –74dBm. This is consistent with –14dB
measured with the ‘scope probe plus an additional 60dB coming from the fluke probe
(x1000).

Note that there is an additional 10dB of attenuation at 1kHz.

Check

Meter reading at 1kHz = 20 Log (28/100) = -11 dB

The two methods agree.

Additional Comment

Placing a grounded object, the probe ground lead or a hand near the red part of the probe,
changed the frequency response of the probe.

Conclusion.

I would not recommend using the Fluke 80K40 above line frequency.

John Barnes, December 29, 2005