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Jasen Betts wrote:
Impossible for power out to be greater than power in. |
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On 2015-10-09, Robert Baer wrote:
Jasen Betts wrote: Impossible for power out to be greater than power in. I said it's a good deal if you don't look too closely. Possibly it's measuring average current and voltage, and not RMS. Or it mught just be reading innacurately. It was like $7 and change for the pair. -- \_(ツ)_ |
3 bux
Jasen Betts wrote:
On 2015-10-09, Robert wrote: Jasen Betts wrote: Impossible for power out to be greater than power in. I said it's a good deal if you don't look too closely. Possibly it's measuring average current and voltage, and not RMS. Or it mught just be reading innacurately. It was like $7 and change for the pair. ....remember, if you DO see a power gain, that you cannot patent it, as the USPTO rejects such patent claims. |
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On 10/9/2015 5:38 AM, Jasen Betts wrote:
On 2015-10-09, Robert Baer wrote: Jasen Betts wrote: Impossible for power out to be greater than power in. I said it's a good deal if you don't look too closely. Possibly it's measuring average current and voltage, and not RMS. Or it mught just be reading innacurately. It was like $7 and change for the pair. Or the in and out labels are in the wrong places and you have an 87% efficient boost DC-DC converter. :-) For what they are, it's really not too bad. 4 meters - $1.50 per meter - with maybe +/- 3.3% error each. At that low cost, they undoubtedly were not "factory calibrated". So if you wanted to take the time and effort, you might be able to spin a pot and file (or add solder to) a shunt to get better accuracy. But really, these meters should be used just to give one a rough idea of voltage & current. Ed |
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On 2015-10-10, ehsjr wrote:
On 10/9/2015 5:38 AM, Jasen Betts wrote: On 2015-10-09, Robert Baer wrote: Jasen Betts wrote: Impossible for power out to be greater than power in. I said it's a good deal if you don't look too closely. Possibly it's measuring average current and voltage, and not RMS. Or it mught just be reading innacurately. It was like $7 and change for the pair. Or the in and out labels are in the wrong places and you have an 87% efficient boost DC-DC converter. :-) For what they are, it's really not too bad. 4 meters - $1.50 per meter - with maybe +/- 3.3% error each. At that low cost, they undoubtedly were not "factory calibrated". So if you wanted to take the time and effort, you might be able to spin a pot and file (or add solder to) a shunt to get better accuracy. But really, these meters should be used just to give one a rough idea of voltage & current. I'll swap them on monday and see if the error moves, and also do some comparisons against some slightly more expensive meters. -- \_(ツ)_ |
3 bux
On 2015-10-10, Jasen Betts wrote:
On 2015-10-10, ehsjr wrote: On 10/9/2015 5:38 AM, Jasen Betts wrote: On 2015-10-09, Robert Baer wrote: Jasen Betts wrote: Impossible for power out to be greater than power in. I said it's a good deal if you don't look too closely. Possibly it's measuring average current and voltage, and not RMS. Or it mught just be reading innacurately. It was like $7 and change for the pair. Or the in and out labels are in the wrong places and you have an 87% efficient boost DC-DC converter. :-) For what they are, it's really not too bad. 4 meters - $1.50 per meter - with maybe +/- 3.3% error each. At that low cost, they undoubtedly were not "factory calibrated". So if you wanted to take the time and effort, you might be able to spin a pot and file (or add solder to) a shunt to get better accuracy. But really, these meters should be used just to give one a rough idea of voltage & current. I'll swap them on monday and see if the error moves, and also do some comparisons against some slightly more expensive meters. Monday update as promised. It turns out that I was shorting out the return path with my scope's earth clip resulting in the supply current being under-reported by about 250mA. +10V -------+----[BUCK]---+-----. | | | | | | | [load] | | | | 0V ---+----[M1]----+-----[M2]---' | v --- | - | ground clip additional isolated powersupply for meter 2 not shown. meter 1 is powered from the +10 -- \_(ツ)_ |
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On 2015-10-10, ehsjr wrote:
For what they are, it's really not too bad. 4 meters - $1.50 per meter - with maybe +/- 3.3% error each. At that low cost, they undoubtedly were not "factory calibrated". So if you wanted to take the time and effort, you might be able to spin a pot and file (or add solder to) a shunt to get better accuracy. Thanks for suggesting that. Close inspection of the rear of he meters revealed tiny open-frame preset pots for both voltage and current trim. The meters now agree with my cheap multimeters, and with each other. The pots seem fairly crummy though, I'm not sure that they will stay set. -- \_(ツ)_ |
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