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Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
Maybe even a 1-amp constant current source with a battery supply, and I can use my DVM on it's 6mV scale (resolution to 0.1mv)...
Thanks!
On Mon, 24 Oct 2005 15:31:01 -0400, William P.N Smith wrote:
Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
You can put a "watch for this" on eBay, and it'll email you when keywords come up in new auctions. Had you aske this a year ago, I would have had one. Ah well...
What are you calling in-expensive. My Fluke 89-IV will do it and much more. It was $400 New. Frequency, AC and DC voltage disp at the same time, Min/Max Hold. Michelle
William P.N. Smith wrote:
Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
Maybe even a 1-amp constant current source with a battery supply, and I can use my DVM on it's 6mV scale (resolution to 0.1mv)...
Thanks!
Dave, How do you "watch for this"? I have looked everywhere on ebay and cannot find it. Michelle
Dave Hinz wrote:
On Mon, 24 Oct 2005 15:31:01 -0400, William P.N Smith wrote:
Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
You can put a "watch for this" on eBay, and it'll email you when keywords come up in new auctions. Had you aske this a year ago, I would have had one. Ah well...
On Mon, 24 Oct 2005 20:22:21 GMT, Michelle P wrote:
Dave, How do you "watch for this"? I have looked everywhere on ebay and cannot find it.
"favorite searches" maybe? I'm not in an ebay-able location at the moment. Ask again if what I gave you just now doesn't get there and I'll look this evening.
"William P.N. Smith" wrote in message
Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
Maybe even a 1-amp constant current source with a battery supply, and I can use my DVM on it's 6mV scale (resolution to 0.1mv)...
Thanks!
google got this one
http://www.professionalequipment.com/xq/ASP/ProductID.3678/id.448/subID.449/qx/default.htm
You must be doing something that I have never experienced.
Use the batteries to privode it's own bias or sensing current using a known heavy load and measure voltage drops just like a real milliohmmeter does it anyway.
Better yet get a low voltage transformer secondary to measure voltage drop across the contact point and measure the voltage drop. A current limiting series component will be required. You can measure the whole battery cell impedance ths way also for battery cell health.
"William P.N. Smith" wrote in message
Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
Maybe even a 1-amp constant current source with a battery supply, and I can use my DVM on it's 6mV scale (resolution to 0.1mv)...
Thanks!
Michelle P wrote:
What are you calling in-expensive.
I dunno, maybe $50 for a 1A current source?
My Fluke 89-IV will do it and much more. It was $400 New. Frequency, AC and DC voltage disp at the same time, Min/Max Hold.
Yeah, I've got the 87-IV, but its' meter leads have 400 milliohms of resistance, and it only reads to 100s of mOhms
"SQLit" wrote:
"William P.N. Smith" wrote in message Anyone have a source for an inexpensive milliohmmeter, maybe as an
http://www.professionalequipment.com/xq/ASP/ProductID.3678/id.448/subID.449/qx/default.htm
Yow, $500 isn't inexpensive, though I'd love to have one!
Mine will zero out (relative mode) to compensate for the lead resistance. It reads to the thousandth of an ohm as well. I I bought the thing several years ago for working on aircraft and I expect to dispose of it in my will in another 40 or so years. It has served me well. I would try e-bay for an old Fluke. I looked they are under Business & Industrial, Industrial & Electrical Test, Test Equipment, Meters, Multimeters.
The Flukes are one of the few that I know of that will read to that accuracy. You could use a different method measuring Voltage and current across the two points, then calculating the resistance V=IR or R=V/I
Michelle
William P.N. Smith wrote:
Michelle P wrote:
What are you calling in-expensive.
I dunno, maybe $50 for a 1A current source?
My Fluke 89-IV will do it and much more. It was $400 New. Frequency, AC and DC voltage disp at the same time, Min/Max Hold.
Yeah, I've got the 87-IV, but its' meter leads have 400 milliohms of resistance, and it only reads to 100s of mOhms
William P.N. Smith wrote:
Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
Maybe even a 1-amp constant current source with a battery supply, and I can use my DVM on it's 6mV scale (resolution to 0.1mv)...
Yup. That's what I did yesterday to check the value of a 0.002 ohm sense resistor. With an ammeter in series with a lab power supply, I adjusted current to 1.00 ampere and the voltage across the unknown resistor measured 2.01 mV. Worked a treat, it did.
--Winston
"Solar Flare" wrote in message
Use the batteries to privode it's own bias or sensing current using a known heavy load and measure voltage drops just like a real milliohmmeter does it anyway.
Better yet get a low voltage transformer secondary to measure voltage drop across the contact point and measure the voltage drop. A current limiting series component will be required. You can measure the whole battery cell impedance ths way also for battery cell health.
That's a good idea. But the user has to be careful to attach the voltmeter to the posts directly so that they don't measure the voltage drop in the contact clips for the test current supply. Not hard, but getting it wrong can lead someone to get all sorts of variations when there's nothing really wrong the the interconnects, just where they're measuring voltage.
daestrom
He is familiar with the four lead method he indicated.
I use this technique with 400A AC to measure resistance of 3000A SF6 and vacuum breakers since the company's too cheap and stupid to understand what it is for....LOL
"daestrom" wrote in message
"Solar Flare" wrote in message Use the batteries to privode it's own bias or sensing current using a known heavy load and measure voltage drops just like a real milliohmmeter does it anyway.
Better yet get a low voltage transformer secondary to measure voltage drop across the contact point and measure the voltage drop. A current limiting series component will be required. You can measure the whole battery cell impedance ths way also for battery cell health.
That's a good idea. But the user has to be careful to attach the voltmeter to the posts directly so that they don't measure the voltage drop in the contact clips for the test current supply. Not hard, but getting it wrong can lead someone to get all sorts of variations when there's nothing really wrong the the interconnects, just where they're measuring voltage.
daestrom
Try checking out some of the Ham Radio and elecronics magazines of the 70's. I remember seeing several simple 4 wire milliohmmeter circuits/projects published back then. There were also a few service-grade instruments made by companies that catered to the consumer electronics and land mobile radio industries that made such a creature that wasn't a very expensive lab instrument. Most of these functioned as short finders. The meters had a center zero and not only would show the short, but the relative direction the probe got from it.
Dave
"Winston" wrote in message
William P.N. Smith wrote: Anyone have a source for an inexpensive milliohmmeter, maybe as an addon to a DVM? I'm starting to look at battery terminals, interconnects, and such, and it'd be nice to have a 4-wire ohm-meter without paying a small fortune for it...
Maybe even a 1-amp constant current source with a battery supply, and I can use my DVM on it's 6mV scale (resolution to 0.1mv)...
Yup. That's what I did yesterday to check the value of a 0.002 ohm sense resistor. With an ammeter in series with a lab power supply, I adjusted current to 1.00 ampere and the voltage across the unknown resistor measured 2.01 mV. Worked a treat, it did.
--Winston
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