Electrochemistry: Liquid Power Resistor for 2000VAC
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From: D from BC on 12 Mar 2010 14:25 In article <hne3hb$taj$1(a)news.eternal-september.org>, Jon_Slaughter(a)Hotmail.com says... > > D from BC wrote: > > In article <hndvkc$ejp$1(a)news.eternal-september.org>, > > Jon_Slaughter(a)Hotmail.com says... > >> > >> D from BC wrote: > >>> I'm setting up a test circuit and I need a 100k resistor that can > >>> handle 2000VAC for a few seconds. > >>> > >>> I was going to run off to the local surplus shop but got the idea of > >>> making a liquid resistor. Saves a trip. > >>> > >>> I added some salt to water and got 100kohm. Copper electrodes (all I > >>> got at the moment). > >>> > >>> Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? > >>> My circuit only needs to run for 5 seconds. > >>> > >>> iows...Does salty water resistance vary with voltage? > >> > >> Why not experiment with it since you already have the setup? Try > >> putting a 100k res in series and measure the voltage. Sweep up to > >> 200VAC and see if the volage devates from 100VAC at the divider. > >> > >> I imagine if the liquid gets hot the resistance will change so you > >> might try an ice bath. You could then try with and without the ice > >> bath and find the deviation to get some temperature dependence > >> relation. > > > > I might. I do have a isolated variable transformer and a single 2W > > 100k resistor. > > And I could try graphite electrodes. I found a pencil. > > > > I'm just wobbling between curiosity /laziness vs practicality. > > To set up an experiment or... forget about that and run off to the > > surplus store and get some real resistors. mmm > > > If it's just for an experiment then why not put the resistor in an ice bath? > I'm not sure how well this will help out but it should easily allow a 1/4W > resistor to last 5 seconds? I imagine the resistor may last 5 seconds > without the bath. The main issue is, of course, that the resistance may > change drastically but you could try it and see. > > Use the 2W 100k resistor in an ice bath and you should be fine. You could > put 200 liquid containers in series or parallel if you really wanted to have > fun ;) I'll do that. Will report later if the 2W 100K with 2000VAC across it failed in cold bath.
From: Jon Slaughter on 12 Mar 2010 15:57 D from BC wrote: > In article <hne3hb$taj$1(a)news.eternal-september.org>, > Jon_Slaughter(a)Hotmail.com says... >> >> D from BC wrote: >>> In article <hndvkc$ejp$1(a)news.eternal-september.org>, >>> Jon_Slaughter(a)Hotmail.com says... >>>> >>>> D from BC wrote: >>>>> I'm setting up a test circuit and I need a 100k resistor that can >>>>> handle 2000VAC for a few seconds. >>>>> >>>>> I was going to run off to the local surplus shop but got the idea >>>>> of making a liquid resistor. Saves a trip. >>>>> >>>>> I added some salt to water and got 100kohm. Copper electrodes >>>>> (all I got at the moment). >>>>> >>>>> Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? >>>>> My circuit only needs to run for 5 seconds. >>>>> >>>>> iows...Does salty water resistance vary with voltage? >>>> >>>> Why not experiment with it since you already have the setup? Try >>>> putting a 100k res in series and measure the voltage. Sweep up to >>>> 200VAC and see if the volage devates from 100VAC at the divider. >>>> >>>> I imagine if the liquid gets hot the resistance will change so you >>>> might try an ice bath. You could then try with and without the ice >>>> bath and find the deviation to get some temperature dependence >>>> relation. >>> >>> I might. I do have a isolated variable transformer and a single 2W >>> 100k resistor. >>> And I could try graphite electrodes. I found a pencil. >>> >>> I'm just wobbling between curiosity /laziness vs practicality. >>> To set up an experiment or... forget about that and run off to the >>> surplus store and get some real resistors. mmm >> >> >> If it's just for an experiment then why not put the resistor in an >> ice bath? I'm not sure how well this will help out but it should >> easily allow a 1/4W resistor to last 5 seconds? I imagine the >> resistor may last 5 seconds without the bath. The main issue is, of >> course, that the resistance may change drastically but you could try >> it and see. >> >> Use the 2W 100k resistor in an ice bath and you should be fine. You >> could put 200 liquid containers in series or parallel if you really >> wanted to have fun ;) > > I'll do that. Will report later if the 2W 100K with 2000VAC across it > failed in cold bath. If you can, monitor the current or use a voltage divider to record the voltage and see how long it takes to change... or record the temperature of the bath.
From: John Larkin on 12 Mar 2010 18:27 On Fri, 12 Mar 2010 10:53:36 -0800, D from BC <myrealaddress(a)comic.com> wrote: >In article <hndvkc$ejp$1(a)news.eternal-september.org>, >Jon_Slaughter(a)Hotmail.com says... >> >> D from BC wrote: >> > I'm setting up a test circuit and I need a 100k resistor that can >> > handle 2000VAC for a few seconds. >> > >> > I was going to run off to the local surplus shop but got the idea of >> > making a liquid resistor. Saves a trip. >> > >> > I added some salt to water and got 100kohm. Copper electrodes (all I >> > got at the moment). >> > >> > Question is... Will this stay 100kohm +/- 10kohm up to 2000VAC? >> > My circuit only needs to run for 5 seconds. >> > >> > iows...Does salty water resistance vary with voltage? >> >> Why not experiment with it since you already have the setup? Try putting a >> 100k res in series and measure the voltage. Sweep up to 200VAC and see if >> the volage devates from 100VAC at the divider. >> >> I imagine if the liquid gets hot the resistance will change so you might try >> an ice bath. You could then try with and without the ice bath and find the >> deviation to get some temperature dependence relation. > >I might. I do have a isolated variable transformer and a single 2W 100k >resistor. >And I could try graphite electrodes. I found a pencil. > >I'm just wobbling between curiosity /laziness vs practicality. >To set up an experiment or... forget about that and run off to the >surplus store and get some real resistors. mmm > I've seen big (as in 50' high, 12 megavolt) Marx generators that used water-filled clear plastic pipes, about like a garden hose, as the capacitor charging resistors. They were blue inside, copper sulphate solution I think. John
From: Vladimir Vassilevsky on 12 Mar 2010 18:42 John Larkin wrote: > I've seen big (as in 50' high, 12 megavolt) Marx generators that used > water-filled clear plastic pipes, about like a garden hose, as the > capacitor charging resistors. They were blue inside, copper sulphate > solution I think. That must be Lenin generator. VLV
From: John Larkin on 12 Mar 2010 19:00
On Fri, 12 Mar 2010 17:42:28 -0600, Vladimir Vassilevsky <nospam(a)nowhere.com> wrote: > > >John Larkin wrote: > > >> I've seen big (as in 50' high, 12 megavolt) Marx generators that used >> water-filled clear plastic pipes, about like a garden hose, as the >> capacitor charging resistors. They were blue inside, copper sulphate >> solution I think. > >That must be Lenin generator. > >VLV I came up with a neat isolated DC-DC converter circuit. I showed it to Phil Hobbs and he called it the Groucho Marx Generator. John |