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use two 6487 to ouptut 1000V

2502, 6485, 6487 - Support
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txz033000
Posts: 13
Joined: October 20th, 2014, 12:58 pm
Country: United States

use two 6487 to ouptut 1000V

Post by txz033000 » December 5th, 2014, 10:26 am

Hi,
I want to output 1000V, but only have two Keithley 6487 at hands. each could output 500V maximum. I wonder if I can link them in serial and output 1000V?

regards,
tao

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: use two 6487 to ouptut 1000V

Post by brian.d.smith » December 5th, 2014, 10:50 am

Here is a a quote from the 6487 data sheet

MAXIMUM COMMON MODE VOLTAGE (between chassis and voltage source or ammeter): 505 VDC.

Yes you can do what you are asking. You will be very close to the maximum. From a safety standpoint, the Lo of the high side 6487 will be at 500V. Operating the Hi side 6487 will be dangerous. You should consider using isolation transformers to power the 6487 instruments.

It would make sense to set the Lo side 6487 to something safe like 1V then set the high side 6487 to 500V. Lastly set the Low side 6487 to 500V. To power down, set the Lo side 6487 to 1V before setting the Hi side 6487 to 0V. I am thinking that you may be touching the instruments to prove the concept. You wold not want to touch an instrument whose Lo is at 500V.

txz033000
Posts: 13
Joined: October 20th, 2014, 12:58 pm
Country: United States

Re: use two 6487 to ouptut 1000V

Post by txz033000 » December 8th, 2014, 8:00 am

Brian,
thanks for the reply. fortunately I located one 2kV voltage supply, so I don't think I need to connect two 6487 to output 1000V. However, I am still thinking to use the - current meter of 6487 to measure the current flow through 2kV voltage supply because the expected current flow should be no more than 200nA. then what I concern now is to protect the - meter. as you mentioned "MAXIMUM COMMON MODE VOLTAGE (between chassis and voltage source or ammeter): 505 VDC". it should be rare to put over 505V on the current meter unless you accidentally directly connect the output of the voltage supply to the current meter. To protect the - meter, I am thinking to put a 1M ohm resistor inside measurement loop , which means the resistor should be in series with the current meter. will this be safe enough?

regards,
tao

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: use two 6487 to ouptut 1000V

Post by brian.d.smith » December 10th, 2014, 6:55 am

Please make a sketch of your proposed setup and post that here.

If you are just using the - ammeter of the 6487, I would ground the Lo of the 6487 input and connect the Hi of the 6487 input to your power supply Lo. The Hi of your power supply would connect to one side of your device under test. The other side of your device under test would connect to Ground. Your power supply Lo must be able to float above ground. No resistors required.

txz033000
Posts: 13
Joined: October 20th, 2014, 12:58 pm
Country: United States

Re: use two 6487 to ouptut 1000V

Post by txz033000 » December 22nd, 2014, 9:32 pm

Brian,
thanks for the reply. actually I started another post asking about how to protect the current meter of my 6487, and got an answer there. but I would still like to post my set-up, in case you have any comment.
Attachments
measurement set up.png
measurement set up.png (246.54 KiB) Viewed 25355 times

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