Open source micro-ampmeter with autorange

Posted on Friday, February 17th, 2012 in project logs by DP

Here’s an open-source micro-ampmeter with autorange. It can measure current from 0.05μA to 10mA. It’s designed on a single layer PCB, making it easy to build with DIY etching techniques:

The micro-ampermeter described here is intended for experimenting with low-power devices. I have just a general multi-meter in my home lab, which is not very convenient to use. The reason for this is that now-days many electronic devices have a power saving mode, where their current consumption drops down in 1-3 orders of magnitude. Measuring current in a device that periodically enters a sleep mode makes it necessary to frequently adjust the multi-meter range, unless it is automatic.

Via Electronics-Lab.

This entry was posted on Friday, February 17th, 2012 at 11:00 pm and is filed under project logs. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

2 Responses to “Open source micro-ampmeter with autorange”

  1. arhi says:

    I like the idea of driving a glass with pcf but I’d go with 3+1 rather then only 3 digits .. I love the idea with TC7660 to help open those mosfets “more”, but I’m not sure I like the choice of shunt resistors, I’d personally go with order of magnitude smaller ones… 4.096V reference source is great (50ppm iirc.. not too bad) but choosing (0R1) 1R, 10R, 100R, 1K would make it for seriously easier math then 8R2 :D .. not to mention that 0.01% 1R is way easier to source then 0.01% 8R2 … I don’t see any calibration button on the schematic so I assume Ron of the mosfets is assumed to be “too low to give a damn”? Since this is a battery operated device, I’d rather go with MAX4239 then with MAX4372. The input offset on the 4239 is 0.1µV typical at room temp while 4372 has 0.3mV input offset!! It is nice that 4372 don’t need gain setting resistors as works as high side current meter with fixed amplification, but taking into account that this is battery operated device you don’t really need high side current sense and can go with a high precission low noise auto zeroing amp… 4372 is made to monitor battery consumption on a laptop or similar device, it was not made to be “very precise” device..

    great project anyhow :D .. great project

  2. High Pitched Capacitors says:

    Isn’t it a micro ammeter?

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