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From: Pegasus [MVP] on 16 Dec 2009 18:05 "Bill Cunningham" <nospam(a)nspam.invalid> schrieb im Newsbeitrag news:u1orN#pfKHA.2104(a)TK2MSFTNGP05.phx.gbl... > > "Paul" <nospam(a)needed.com> wrote in message news:hgaf83$lf8$1(a)aioe.org... > >> The ESD wrist strap, is for safely helping to bring things to the >> same potential (equipotential). Yes, it is a better solution while >> working on the computer, than zapping things with your fingers. >> At one time, a RAM purchase may have included a paper (disposable) >> wrist strap. Having your own proper wrist strap, means being >> able to reuse it at a future date. > > Is there any way to run a voltage or continuity test with a multi meter > on the ram sticks? To see if they're good. > > Bill No, there isn't. Attacking a memory stick with a multimeter is equivalent to tapping your skull with a hammer. It may ring but you won't find out if it functions normally.
From: Paul on 16 Dec 2009 21:33 Bill Cunningham wrote: > "Paul" <nospam(a)needed.com> wrote in message news:hgaf83$lf8$1(a)aioe.org... > >> The ESD wrist strap, is for safely helping to bring things to the >> same potential (equipotential). Yes, it is a better solution while >> working on the computer, than zapping things with your fingers. >> At one time, a RAM purchase may have included a paper (disposable) >> wrist strap. Having your own proper wrist strap, means being >> able to reuse it at a future date. > > Is there any way to run a voltage or continuity test with a multi meter > on the ram sticks? To see if they're good. > > Bill > I can't think of any good tests. If you're seeing just a few errors for example, that suggests exterior (visible) electrical issues aren't the problem, and the problem is inside one of the RAM chips. If the module gave a clean failure in some way, then you might deduce from that, that there was an open series damping resistor or a bad solder joint. But the majority of failures are going to involve something inside the RAM chip. So the multimeter doesn't tell us a lot. Paul
From: Pegasus [MVP] on 17 Dec 2009 00:28 "Paul" <nospam(a)needed.com> schrieb im Newsbeitrag news:hgc57p$pno$1(a)aioe.org... > Bill Cunningham wrote: >> "Paul" <nospam(a)needed.com> wrote in message news:hgaf83$lf8$1(a)aioe.org... >> >>> The ESD wrist strap, is for safely helping to bring things to the >>> same potential (equipotential). Yes, it is a better solution while >>> working on the computer, than zapping things with your fingers. >>> At one time, a RAM purchase may have included a paper (disposable) >>> wrist strap. Having your own proper wrist strap, means being >>> able to reuse it at a future date. >> >> Is there any way to run a voltage or continuity test with a multi >> meter on the ram sticks? To see if they're good. >> >> Bill >> > > I can't think of any good tests. If you're seeing just a few errors > for example, that suggests exterior (visible) electrical issues aren't > the problem, and the problem is inside one of the RAM chips. If the module > gave a clean failure in some way, then you might deduce from that, > that there was an open series damping resistor or a bad solder joint. > But the majority of failures are going to involve something inside > the RAM chip. So the multimeter doesn't tell us a lot. > > Paul > The multimeter test might destroy the RAM chip, like the tap on the head with the hammer. I find it difficult to think of a more inappropriate test for a RAM chip. Remember - it contains a hundred million or more transistor gates operating at extremely low currents, less than the most sensitive multimeter can detect!
From: Bill in Co. on 17 Dec 2009 02:39 Pegasus [MVP] wrote: > "Paul" <nospam(a)needed.com> schrieb im Newsbeitrag > news:hgc57p$pno$1(a)aioe.org... >> Bill Cunningham wrote: >>> "Paul" <nospam(a)needed.com> wrote in message >>> news:hgaf83$lf8$1(a)aioe.org... >>> >>>> The ESD wrist strap, is for safely helping to bring things to the >>>> same potential (equipotential). Yes, it is a better solution while >>>> working on the computer, than zapping things with your fingers. >>>> At one time, a RAM purchase may have included a paper (disposable) >>>> wrist strap. Having your own proper wrist strap, means being >>>> able to reuse it at a future date. >>> >>> Is there any way to run a voltage or continuity test with a multi >>> meter on the ram sticks? To see if they're good. >>> >>> Bill >>> >> >> I can't think of any good tests. If you're seeing just a few errors >> for example, that suggests exterior (visible) electrical issues aren't >> the problem, and the problem is inside one of the RAM chips. If the >> module >> gave a clean failure in some way, then you might deduce from that, >> that there was an open series damping resistor or a bad solder joint. >> But the majority of failures are going to involve something inside >> the RAM chip. So the multimeter doesn't tell us a lot. >> >> Paul >> > > The multimeter test might destroy the RAM chip, like the tap on the head > with the hammer. I find it difficult to think of a more inappropriate test > for a RAM chip. Remember - it contains a hundred million or more > transistor > gates operating at extremely low currents, less than the most sensitive > multimeter can detect! Beyond that, it's the wrong tool for the job, no matter how sensitive it is. There is no way a multimeter could test an integrated circuit. What would be needed is an IC tester, and that would be specific for that type of chip, as there is no such thing as a universal IC tester. The only practical way to test a suspected IC chip for a consumer would be by substitution with another one to see if that works.
From: Paul on 17 Dec 2009 05:06
Pegasus [MVP] wrote: > > > The multimeter test might destroy the RAM chip, like the tap on the head > with the hammer. I find it difficult to think of a more inappropriate > test for a RAM chip. Remember - it contains a hundred million or more > transistor gates operating at extremely low currents, less than the most > sensitive multimeter can detect! You can safely test silicon devices, if you use a multimeter with "low power ohms" setting. It applies a voltage not intended to cause forward conduction in the silicon chips. If you lost the manual for your multimeter, you can verify this by using two multimeters. One multimeter set to "ohms". The second multimeter set to "volts". The "volts" multimeter will show you a rough idea of the open circuit voltage that the "ohms" meter is putting out. (Connect red to red, black to black.) Test all the "ohms" ranges on the meter, to understand which ranges are "high power" and "low power". If an ohms range doesn't put out more than 1 volt open circuit, then it should be relatively safe to use on just about anything. For the highest resistance ranges, the results need some interpretation (since the voltmeter has a finite input impedance of its own) The $100 The $20 meter meter Range Ohmmeter Voltmeter Assumed Confidence Reads Reads Power type Beep Infinity 2.66V High Diode infinity 2.67V High High on purpose, for diode test 200 Infinity 1.01V Low 2K infinity 1.01V Low 20K Infinity 0.48V Low 200K infinity 0.43V Low 2M "0.995" 0.23V Low OK, see interpretation 20M "0.99" 0.04V Low 2000M "001" 0.27V ??? suspicious (Note - a separate set of tests were done, and the "ohms" multimeter never applied more than 1 milliamp of current to the test leads. Typical silicon clamp diodes are rated for about 10 milliamps. So there is no danger from the level of current flow either.) In the 2 megohm test case, the "volts" multimeter appears to have only a 1 megohm input impedance. Half of the open circuit voltage is across the "volts" multimeter, and half is across the constant current source inside the meter. We could conclude from that, that the actual open circuit voltage applied by the multimeter, is 2 * 0.23 volts or 0.46V. And that is suitable for low power ohms. So you actually have to stare at the display on both devices to understand what is going on. My suspicion is, the "insulation test" range on my multimeter, is actually high power ohms. It is pretty hard to test insulation, with a low voltage. Insulation testing would normally be done with a "megger". Since I am suspicious of what I see for the 2000M range, I likely would not switch to it while working on the average PCB. There are quality voltmeters, with much higher input impedance than my $20 "volts" multimeter used in this test. For such a device (perhaps a $1000 unit), I likely would not need interpretation except for the last test case. And the voltmeter in that case, could tell me what the open circuit voltage is, correctly, for the rest of the ranges. The $20 meter is the one I lend to friends :-) So there are six ranges on my $100 multimeter, that I'd use on a DIMM. Without being concerned about any side effects to the silicon. Some older meters, like my analog Simpson, are a bit meaner. They apply nine volts open circuit, and would be unsuited for this purpose. I could have run the same set of tests for my Simpson, but there is no point, because I simply wouldn't use it. My Simpson is good for volts "trend analysis", as digital meters aren't perfect for all purposes. There are still occasions for reaching for my oldest multimeter. "Ohms" would not be one of those reasons. If a person had concerns about any silicon device they were working on, they could look in the datasheet for inspiration. I haven't done that in this case for the memory chip. I'm reasonably confident, that the six tested ranges on my multimeter, would be safe enough. HTH, Paul |