Timeline for INA828 for sensing current down to tens of nA
Current License: CC BY-SA 4.0
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| Nov 17 at 11:37 | comment | added | Andy aka | I'm sorry @spanito but I'm returning (rolling-back) the question to how it originally stood. Once you have received answers you should not amend your question without checking that the amendment doesn't make given answers look stupid. I suggest you start a new post and open up a new question to the whole floor. | |
| Nov 17 at 11:31 | comment | added | spanito | I have modified the post adding a second proposal of the circuit. This will ensure that the difference between common mode voltage and output voltage will be only few hundreds of mV and should avoid saturation in the INA828. Do you think this would actually work? | |
| Nov 17 at 3:03 | comment | added | spanito | I use a 3.7V LiPo battery that provides Vd and GND1 to a PCB with multiple sense Resistors with 0.1% tolerance and a bypass. Sense Resistors can be enabled/disabled with Jumpers. The DUT is an Attiny85 or a TPL5110. I initially select the bypass to start the DUT, I put it in deep sleep and then select the appropriate sense resistor. I believe that at nA current levels the DMM input resistance is not high enough. Hence I was looking for a buffer or OPA with very high input DC resistance. I do not need to log the data to a PC or other device, so a DMM with an LCD display is enough for me. | |
| Nov 16 at 19:46 | comment | added | Spehro 'speff' Pefhany | You would need to describe your actual setup in some detail in order for me (or anyone else, I suspect) to give a sensible answer to that. The 200mV voltage range on a typical DMM is actually a nA range if you look at it sideways. With a 10MΩ input resistance it is 19.99nA full scale. You could parallel the 10M (assuming that's correct) resistance on the same voltage range with nominally 10/9 MΩ to make it +/-199.9nA full scale. | |
| Nov 16 at 18:30 | comment | added | spanito | Thanks for your very detailed answer. How would I implement a circuit that can always keep GND2 and (Vd-I*R/2) within about +/-3.5V of each other as shown in the figure you posted? I have used so far a low cost digital multimeter, but my understanding is that even more expensive ones have an input resistance that is not high enough, thus affecting the measurement. Do you think using a battery powered multimeter would be better that using the INA828? | |
| Nov 16 at 17:48 | history | edited | Spehro 'speff' Pefhany | CC BY-SA 4.0 |
added 272 characters in body
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| Nov 16 at 17:39 | history | answered | Spehro 'speff' Pefhany | CC BY-SA 4.0 |