On a sunny day (Sat, 23 Sep 2023 05:32:55 -0700 (PDT)) it happened Eddy Lee <eddy711lee@gmail.com> wrote in <4da5b75c-8e11-4689-bbef-9fde0d5f9499n@googlegroups.com>:>I often have to measure the difference of two 392V sources. Unfortunately, sometimes it become the sum, using a one-time fused >muti-meter. > >I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms >resistor. > >Will it work? Perhaps 22 or 33 ohms resistor?Specially for HV I bought a few dollar (5 USD or so) little analog multimeter after I blew up a digital one measuring a few kV in a PMT supply https://panteltje.nl/pub/cheap_meter.jpg It does not seem to care much about voltage overload...
HV indicator
Started by ●September 23, 2023
Reply by ●September 24, 20232023-09-24
Reply by ●September 24, 20232023-09-24
On Saturday, September 23, 2023 at 9:36:10 AM UTC-4, Eddy Lee wrote:> On Saturday, September 23, 2023 at 6:00:58 AM UTC-7, Fred Bloggs wrote: > > On Saturday, September 23, 2023 at 8:33:01 AM UTC-4, Eddy Lee wrote: > > > I often have to measure the difference of two 392V sources. Unfortunately, sometimes it become the sum, using a one-time fused muti-meter. > > > > > > I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms resistor. > > > > > > Will it work? Perhaps 22 or 33 ohms resistor? > > This would be fun, and quick to build: > > > > https://www.homemade-circuits.com/high-voltage-meter-circuit-for-measuring-10kv/ > > > > The CA3140 is widely available and costs just a buck: > > > > https://www.renesas.com/us/en/document/dst/ca3140-ca3140a-datasheet > > > > You don't need to mess with those rheostats shown on the diagram, those are for calibrating that ancient 100uA FS meter. > This will measure high voltage, but my goal is really measuring low voltage (+/- 6V to 12V), with protection from high voltage. Blowing the light bulb is fine.The CA3140 circuit, which is copied from a 1960s RCA app not I'm sure, when modified as I suggested will measure the difference in your small voltage range quite accurately. You don't like circuit complexity, so a zero output reading will have to be confirmed by interchanging the HV leads. The underlying principle is two voltage sources V1 and V2 at either side of a resistance V1--R--V2 results in a current |V1-V2|/R through the resistance. That looks a lot like an opportunity to measure a difference in voltages to me. But if you like using 1000s times more power than necessary to make a simple measurement, lots of incandescent bulbs, HV diodes, and high power components, to end up with a system producing an indication with 50% accuracy or less, have at it.
Reply by ●September 24, 20232023-09-24
On Saturday, September 23, 2023 at 6:59:57 PM UTC-4, whit3rd wrote:> On Saturday, September 23, 2023 at 11:37:49 AM UTC-7, Eddy Lee wrote: > > On Saturday, September 23, 2023 at 10:49:20 AM UTC-7, whit3rd wrote: > > > On Saturday, September 23, 2023 at 5:33:01 AM UTC-7, Eddy Lee wrote: > > > > I often have to measure the difference of two 392V sources. Unfortunately, sometimes it becomes the sum, using one-time fused muti-meter. > > > > > > > > I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms resistor. > > > > > > > > Will it work? Perhaps 22 or 33 ohms resistor? > > > Or maybe a 220k ohm resistor and a neon lamp? > > Did it light up well between 3V and 12V? I can tell when there is around 3V across the 6V light bulb. > There's some crude multilamp variants that can tell 120VAC from 240 from 480... > it gives enough info to rethink what meter (or meter setting) to use for the real > measurement thereafter. Neon doesn't glow at under 50V or so. > > That relatively high strike voltage is how it can give a good glow indication off > high voltages without drawing much current, using no battery.Some multimeters, in particular EXTECH, have a Non-Contact Voltage (NCV) Detector in the form of an ionizing gas bulb that lights for VAC in the range 100-600 Volts AC. These are available in the big box stores off the shelf / display hook. https://www.flir.com/products/ex330/
Reply by ●September 24, 20232023-09-24
On Saturday, September 23, 2023 at 10:55:34 PM UTC-7, Jan Panteltje wrote:> On a sunny day (Sat, 23 Sep 2023 05:32:55 -0700 (PDT)) it happened Eddy Lee > <eddy7...@gmail.com> wrote in > <4da5b75c-8e11-4689...@googlegroups.com>: > >I often have to measure the difference of two 392V sources. Unfortunately, sometimes it become the sum, using a one-time fused > >muti-meter. > > > >I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms > >resistor. > > > >Will it work? Perhaps 22 or 33 ohms resistor? > Specially for HV I bought a few dollar (5 USD or so) little analog multimeter after I blew up a digital one measuring a few kV in a PMT supply > https://panteltje.nl/pub/cheap_meter.jpg > > It does not seem to care much about voltage overload...I blew up a few of these, even for the older version with HV of 1000V. The newer one is 200V. Sometimes, the damage is not immediate. After a while, i got strange voltage readings. https://www.harborfreight.com/7-function-digital-multimeter-63759.html
Reply by ●September 24, 20232023-09-24
On Sunday, September 24, 2023 at 5:40:16 AM UTC-7, Fred Bloggs wrote:> Some multimeters, in particular EXTECH, have a Non-Contact Voltage (NCV) Detector in the form of an ionizing gas bulb that lights for VAC in the range 100-600 Volts AC. > > These are available in the big box stores off the shelf / display hook. > > https://www.flir.com/products/ex330/My Greenlee GT-11 non contact detector is a capacitive pickup and lights an LED; it only senses AC.
Reply by ●September 24, 20232023-09-24
On Sunday, September 24, 2023 at 4:17:02 PM UTC-4, whit3rd wrote:> On Sunday, September 24, 2023 at 5:40:16 AM UTC-7, Fred Bloggs wrote: > > > Some multimeters, in particular EXTECH, have a Non-Contact Voltage (NCV) Detector in the form of an ionizing gas bulb that lights for VAC in the range 100-600 Volts AC. > > > > These are available in the big box stores off the shelf / display hook. > > > > https://www.flir.com/products/ex330/ > My Greenlee GT-11 non contact detector is a capacitive pickup and lights an LED; it > only senses AC.Greenlee? You don't mess around, that's one of the best out there.
Reply by ●September 24, 20232023-09-24
On 2023-09-23, Eddy Lee <eddy711lee@gmail.com> wrote:> On Saturday, September 23, 2023 at 3:59:57 PM UTC-7, whit3rd wrote: >> On Saturday, September 23, 2023 at 11:37:49 AM UTC-7, Eddy Lee wrote: >> > On Saturday, September 23, 2023 at 10:49:20 AM UTC-7, whit3rd wrote: >> > > On Saturday, September 23, 2023 at 5:33:01 AM UTC-7, Eddy Lee wrote: >> > > > I often have to measure the difference of two 392V sources. Unfortunately, sometimes it becomes the sum, using one-time fused muti-meter. >> > > > >> > > > I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms resistor. >> > > > >> > > > Will it work? Perhaps 22 or 33 ohms resistor? >> > > Or maybe a 220k ohm resistor and a neon lamp? >> > Did it light up well between 3V and 12V? I can tell when there is around 3V across the 6V light bulb. >> There's some crude multilamp variants that can tell 120VAC from 240 from 480... >> it gives enough info to rethink what meter (or meter setting) to use for the real >> measurement thereafter. Neon doesn't glow at under 50V or so. >> >> That relatively high strike voltage is how it can give a good glow indication off >> high voltages without drawing much current, using no battery. > > But what I want is to tell the difference between two 392V sources, usually +/- 12V floating on top of 392V. However, sometimes it get mis-wired into sum, or 784V. In that case, it's OK to blow the bulb like a fuse.a 6V lamp on 700V will probably blow like a 12V fuse does in the same circumstance (explosively), I suspect you would say not ok. Just buy a 1000V auto-ranging multimeter, with whatever measurement catergory is suited to traction batteries (I'm guessing probably Cat.IV ) -- Jasen. 🇺🇦 Слава Україні
Reply by ●September 24, 20232023-09-24
On Sunday, September 24, 2023 at 7:00:48 PM UTC-7, Jasen Betts wrote:> On 2023-09-23, Eddy Lee <eddy7...@gmail.com> wrote: > > On Saturday, September 23, 2023 at 3:59:57 PM UTC-7, whit3rd wrote: > >> On Saturday, September 23, 2023 at 11:37:49 AM UTC-7, Eddy Lee wrote: > >> > On Saturday, September 23, 2023 at 10:49:20 AM UTC-7, whit3rd wrote: > >> > > On Saturday, September 23, 2023 at 5:33:01 AM UTC-7, Eddy Lee wrote: > >> > > > I often have to measure the difference of two 392V sources. Unfortunately, sometimes it becomes the sum, using one-time fused muti-meter. > >> > > > > >> > > > I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms resistor. > >> > > > > >> > > > Will it work? Perhaps 22 or 33 ohms resistor? > >> > > Or maybe a 220k ohm resistor and a neon lamp? > >> > Did it light up well between 3V and 12V? I can tell when there is around 3V across the 6V light bulb. > >> There's some crude multilamp variants that can tell 120VAC from 240 from 480... > >> it gives enough info to rethink what meter (or meter setting) to use for the real > >> measurement thereafter. Neon doesn't glow at under 50V or so. > >> > >> That relatively high strike voltage is how it can give a good glow indication off > >> high voltages without drawing much current, using no battery. > > > > But what I want is to tell the difference between two 392V sources, usually +/- 12V floating on top of 392V. However, sometimes it get mis-wired into sum, or 784V. In that case, it's OK to blow the bulb like a fuse. > a 6V lamp on 700V will probably blow like a 12V fuse does in the same > circumstance (explosively), I suspect you would say not ok.I blew one at around 10V, the filament vaporized but the glass container is OK. There was a bright flash, but no explosion.> Just buy a 1000V auto-ranging multimeter, with whatever measurement > catergory is suited to traction batteries (I'm guessing probably > Cat.IV )I got one, but how do we know that it's really safe for 784V.> -- > Jasen. > 🇺🇦 Слава УкраїніF35/F16/ATACMS for UA.
Reply by ●September 25, 20232023-09-25
On a sunny day (Sun, 24 Sep 2023 10:14:04 -0700 (PDT)) it happened Eddy Lee <eddy711lee@gmail.com> wrote in <3eaa7a30-a853-471a-b1af-405cb1ebbd6bn@googlegroups.com>:>On Saturday, September 23, 2023 at 10:55:34 PM UTC-7, Jan Panteltje= > wrote: >> On a sunny day (Sat, 23 Sep 2023 05:32:55 -0700 (PDT)) it happened Eddy L= >ee >> <eddy7...@gmail.com> wrote in >> <4da5b75c-8e11-4689...@googlegroups.com>: >> >I often have to measure the difference of two 392V sources. Unfortunatel= >y, sometimes it become the sum, using a one-time fused >> >muti-meter. >> > >> >I am thinking about using a rectifier diode (for direction) , 6V zener (= >for voltage), 6V 5W light bulb (for current) and 10 ohms >> >resistor. >> > >> >Will it work? Perhaps 22 or 33 ohms resistor? >> Specially for HV I bought a few dollar (5 USD or so) little analog multim= >eter after I blew up a digital one measuring a few kV in a PMT supply >> https://panteltje.nl/pub/cheap_meter.jpg >> >> It does not seem to care much about voltage overload... > >I blew up a few of these, even for the older version with HV of 1000V. The= > newer one is 200V. Sometimes, the damage is not immediate. After a while= >, i got strange voltage readings. > >https://www.harborfreight.com/7-function-digital-multimeter-63759.htmlYea, I do not keep it connected for any length of time though... And PMT circuits do not have a high current capability. I blew up a nice digital one that was accidently on the Ohms range a few weeks ago I expected the chip was dead, but investigation found just a 900 Ohm SMD resistor open circuit. I replaced it by 680 and 220 Ohm in series... Reading is perfect again... How I found out it should be 900 Ohm? divider circuit measured (with an other meter of course) 90 ? 9000 etc, so that in-between range had to be be 900. Actually have an other analog one from ebay now: https://www.ebay.com/itm/250977645828 But with 4 digital ones from ebay that I payed just a few dollars for (model was recommended by somebody here) I have more meters than I need, some still in the box as spare. https://panteltje.nl/pub/chinese_multimeter_img_3159.jpg that was the one I fixed the 900 Ohm in... Used every day, but does not like HV. [
Reply by ●September 25, 20232023-09-25
On 24/09/2023 6:14 pm, Eddy Lee wrote:> On Saturday, September 23, 2023 at 10:55:34 PM UTC-7, Jan Panteltje wrote: >> On a sunny day (Sat, 23 Sep 2023 05:32:55 -0700 (PDT)) it happened Eddy Lee >> <eddy7...@gmail.com> wrote in >> <4da5b75c-8e11-4689...@googlegroups.com>: >>> I often have to measure the difference of two 392V sources. Unfortunately, sometimes it become the sum, using a one-time fused >>> muti-meter. >>> >>> I am thinking about using a rectifier diode (for direction) , 6V zener (for voltage), 6V 5W light bulb (for current) and 10 ohms >>> resistor. >>> >>> Will it work? Perhaps 22 or 33 ohms resistor? >> Specially for HV I bought a few dollar (5 USD or so) little analog multimeter after I blew up a digital one measuring a few kV in a PMT supply >> https://panteltje.nl/pub/cheap_meter.jpg >> >> It does not seem to care much about voltage overload... > > I blew up a few of these, even for the older version with HV of 1000V. The newer one is 200V. Sometimes, the damage is not immediate. After a while, i got strange voltage readings. > > https://www.harborfreight.com/7-function-digital-multimeter-63759.htmlSo you can either buy a better meter rated to 1000V or build a resistor 10:1 attentuator and keep using cheap meters. Minimally use the meter input impedance and just enough series resistance to get 10:1 piglet
