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Products => Test Equipment => Topic started by: harrimansat on December 26, 2019, 08:03:33 pm

Title: HP34401 low input impedance and maximum voltage question
Post by: harrimansat on December 26, 2019, 08:03:33 pm
I´m fixing a HP34401, someone with the same multimeter can please check if impedance above 20 volts is 100k?

Attached photo is voltage input at 10V scale 10 Mohms selected, connected at Tektronix 576 curve tracer.

With more of 20V impedance is 100k?

Manual says 1000v max voltage but nothing about impedance.

Thanks

Regards
Title: Re: HP34401 low input impedance and maximum voltage question
Post by: Kleinstein on December 26, 2019, 08:25:58 pm
The input specs are some 100 K beyond some +-17 V for the 0.1 to 10 V ranges. This also makes sense looking at the schematics.

The opening in the center is likely due to the input capacitance.
Title: Re: HP34401 low input impedance and maximum voltage question
Post by: rolkinas on January 11, 2020, 12:14:31 am
on mine 34401A:
1Vdc to 1000Vdc impedance stays 10 Mohm (input R selected to be 10 Mohm )

1V - 0.1uA
10V - 1 uA
100V - 10uA
1000V - 100uA
(measured with Keithley 237)

Switcing input R to 10 Gohm
it stays high impedance 0-12Vdc
above 12Vdc input R switches to 10 Mohm
Title: Re: HP34401 low input impedance and maximum voltage question
Post by: harrimansat on January 13, 2020, 04:45:57 pm
Quote from: rolkinas on January 11, 2020, 12:14:31 am
on mine 34401A:
1Vdc to 1000Vdc impedance stays 10 Mohm (input R selected to be 10 Mohm )

1V - 0.1uA
10V - 1 uA
100V - 10uA
1000V - 100uA
(measured with Keithley 237)

Switcing input R to 10 Gohm
it stays high impedance 0-12Vdc
above 12Vdc input R switches to 10 Mohm

Thanks, but in 1V and 10V scale, with voltaje greater than 17V wich is the impedance?
Title: Re: HP34401 low input impedance and maximum voltage question
Post by: rolkinas on January 13, 2020, 05:20:46 pm
when 10M input impedance in meniu is set, actual impedance at 30Vdc through mV, 1V, 10V ranges appears to be 300kohm

100V and 1000V are steady 10Mohm. Of course 34401A displays OV.LD in lover ranges with 30V on input
Transition from 10Mohm to 300k is at 20Vdc
Title: Re: HP34401 low input impedance and maximum voltage question
Post by: harrimansat on January 17, 2020, 05:43:20 pm
Scale swtiching time and impedance at VDCHI