Hi all,
Apologies in advance is this may seem a naive question, or if it has been covered before.

I am a Physical Chemist, working at a Uni in Australia, and I need to have some voltage supplies for electrostatic lenses of a mass spectrometer. The supplies need to be bipolar, and be tunable from -100V to 100V out of the one channel (i.e. not unplugging the leads). In all I need four independent supplies. The current would be very low, as the electrostatic lenses are isolated from ground.

A group I worked with in Germany had six electronics gurus who made these things, however here I have not much support!

What I am looking for is an answer to the question, can these be made easily? Does anyone have an idea on how this can be done?

I would really appreciate your help!

 

By the way, I said that I was a Physical Chemist to highlight the fact that I am a simpleton when it comes to electronics!

 

Can you get the circuit diagram from the previous electronics guys?, as it's a proven working design it seems silly to reinvent the wheel?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Hi Nigel,
thanks for getting back to me. Unfortunately, they are not being very forthcoming with the schematics. I have asked a few times, and been fobbed off. I will ask again, however I am not hopeful!

Just wanted to see if anyone had an idea of how to do it, as I am challenged when it comes to these things.

 

Can be done, how low (ie current) are we talking here?

 

G'day specie,

Thanks for your post! Here I will show my lack of knowledge... As the plates that I wish to apply the voltage to are isolated from ground, am I right in thinking that the only current flow will be due to the slight capacitance that the plates will have? By this I mean that the current will flow only during the initial charging of the plates?

I have not calculated the capacitance, however I have a journal article that has some equations for doing this for different plate shapes etc (i.e. whether they are circular, rectangular, etc)
Yuanshun Chi, European Journal of Physics, volume 17 pages 363-364

For a different application, with bigger plates than the ones I plan to use here, I calculated a capacitance of 5.5 pico Farad.

From this, I would imagine that the current flow would be negligible.

Cheers!

 

G'day again,

Apologies for the next "stupid" question, however can I get a feeling from you all of what is considered to be a "low current"? My thinking would be that 500µA or below would be a low current, am I right?

Cheers!

 

That's pretty low, but the lower it is, the easier it is to do. What sort of temperature stability do you need (ppm/deg C or %/deg C)?

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Ron (aka Rube)

 

G'day Roff,

Thanks for your reply. By temperature stability, do you mean the stability of the voltage output with respect to environmental temperature (i.e. of the lab), or the stability of the components?

I would think that as long as the voltage did not change by 0.1% over the day, then this would be fine.

Cheers!

 

Is it being used in a stable temperature environment? I'm assuming that a lab would be air conditioned (or whatever the local term is ).

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Ron (aka Rube)

 

The lab is air conditioned, and will not change much throughout the day.

What would you consider stable? +/- 5 degs?

 

That's good enough. Do you have 220V mains? I think you can see I'm leading up to something here.

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Ron (aka Rube)

 

Yep I do (have 220V), and how much does the unit you produce cost?? Or is this not what you were leading up to??

(Apologies if this appears cheeky..)

 

LOL!
No, I don't produce anything. I just have a fairly simple design that might work.
I have it designed, but I need to do a little research on components before I post it, and unfortunately it's past my bed time.
I'll get back to it some time tomorrow.

__________________
Ron (aka Rube)

 

Hey DrDunk,
You do not come across as a complete ignorant in electronics . Anyway, with the conditions you specified, it will not be much of a problem. Will get back to you with a circuit latest monday. I do not have access to the net on weekends