Timeline for Measuring high-side vs low-side current, different readings?
Current License: CC BY-SA 4.0
21 events
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| Dec 10, 2020 at 20:58 | history | edited | wolf9000 | CC BY-SA 4.0 |
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| Dec 9, 2020 at 0:48 | answer | added | Alexander Stohr | timeline score: 0 | |
| Dec 8, 2020 at 16:32 | comment | added | wolf9000 | From eepower, "When the circuit shares a common ground with the measurement device, often is chosen to place the shunt as close to the ground as possible. The reason is to protect the ammeter from the common mode voltage that might be too high and damage the device or give erroneous results. A disadvantage from this set up is that leakages that bypass the shunt might not be detected." These are probably the leaks I am trying to understand, so it is possible? | |
| Dec 8, 2020 at 16:04 | answer | added | Simon B | timeline score: 1 | |
| Dec 8, 2020 at 16:02 | comment | added | wolf9000 | Digital multimeter. This happens only with a single device. Battery cell wires are AWG20, unsure about the device side. | |
| Dec 8, 2020 at 16:00 | history | edited | wolf9000 | CC BY-SA 4.0 |
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| Dec 8, 2020 at 15:59 | comment | added | Hearth | Is this an analog or digital ammeter? If it's analog, assuming you're physically repositioning the instrument, stray magnetic fields could be influencing it. | |
| Dec 8, 2020 at 15:59 | comment | added | wolf9000 | I'm doing relatively short tests, so I do not think anything gets heated much above standard room temperature. Sorry for the fuss. My original intent was to ask mostly a reality question of whether there exists a circuit, however flawed or sophisticated, that can produce this difference. | |
| Dec 8, 2020 at 15:54 | history | edited | wolf9000 | CC BY-SA 4.0 |
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| Dec 8, 2020 at 15:54 | comment | added | Solar Mike | Are any components changing temperature during and / or between tests? | |
| Dec 8, 2020 at 15:53 | history | edited | wolf9000 | CC BY-SA 4.0 |
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| Dec 8, 2020 at 15:46 | comment | added | StainlessSteelRat | I agree with Andy. You need to draw a circuit, because there is ambiguity in your words. There is a schematic editor in the editor. Looks like circuit components. Do you disconnect battery from load and connect ammeter between battery and load? | |
| Dec 8, 2020 at 15:45 | comment | added | wolf9000 | Is it possible that the circuit has capacitors which are being charged and discharged in a certain way, which might explain the difference of 1...2 mA of "+" and "-" current at the battery? | |
| Dec 8, 2020 at 15:39 | comment | added | wolf9000 | If the ammeter's terminals are inverted, the absolute value of the measurement remains the same. However, I am still seeing the discrepancy of the absolute value between "+" and "-". The calculator that has a discrepancy has a small solar panel. Is it possible that 1...2 mA is somehow backfeeding into the solar panel and that is why I am not seeing it at the "-" of the battery? Update: I have disconnected the solar panel and I am still seeing the difference. | |
| Dec 8, 2020 at 15:31 | comment | added | Sredni Vashtar | But does the current always flow in the same direction in the ammeter when you measure at the + and at the - pole? I mean, have you tried inverting the ammeter's terminals when you are measuring current at the same pole? Same measurement? | |
| Dec 8, 2020 at 15:21 | comment | added | wolf9000 | I do not have the schematics on the device side since the devices are just a bunch of random end user devices I have lying around. I am asking whether any blackbox device can have this behavior ([protection] diodes [leakage], etc) when battery drain current is being measured, or is there an e.g. fundamental difference between measuring current via + or - on the battery. My assumption, and everything that I have read so far, says that there should not be any difference. It seems to be device-specific. On most devices, the current is equal. | |
| Dec 8, 2020 at 15:12 | comment | added | wolf9000 | (1.) The same instrument (2.) Repeated 5 times or more. (3.) Some devices include charging, then the current is positive. Otherwise, the battery is draining (the current is negative). (4.) The measurement is done by splitting the + wire of the battery in half, and putting the multimeter in-between, while - remains connected straight to the device. Then visa-versa. The measurements of + and - are not done at the same time. | |
| Dec 8, 2020 at 15:11 | comment | added | Sredni Vashtar | So, you put your ammeter in series with the batteries, only one time at the + pole, and the other time at the - pole? Are you using the same instrument at different times? Did you retake measurements several times to confirm the discrepancy is consistent? Does the current always flow in the same sense through the instrument? | |
| Dec 8, 2020 at 14:30 | comment | added | Andy aka | A schematic is needed to clear the ambiguity of your words. | |
| Dec 8, 2020 at 13:46 | review | First posts | |||
| Dec 8, 2020 at 15:26 | |||||
| Dec 8, 2020 at 13:41 | history | asked | wolf9000 | CC BY-SA 4.0 |