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Member #693354

Member Since: June 20, 2015

Country: United States

  • I'm trying to use the Coulomb Counter Breakout Board as the foundation of an instrument to measure the current used by a low current (<100uA) device under test (DUT). Everything works great until I try measuring currents down below 10mA. The LTC4150 adds 115uA (LTC4150 datasheet page 3) to any measurement so while trying to measure <1mA there's of an error of >10% in the value I want to measure (I didn't care when measuring >10mA since that's a <1% error). To change this I think I need to:

    1. Change the 0.05 Ohm resistor to a 0.50Ohm resistor (changing max current to 100mA). Is the 0.05Ohm resistor an 0805 size? I want to order the correct replacement.

    2. Cut the VDD trace, but not wire it to Vio (see #3 below). Where should I make the cut so I can wire to it to power the LTC4150 separately? (Member #489794 wanted to do the same thing. How did that go?)

    3. The LTC4150 datasheet states: SENSE+ must be within 60mV of Vdd for proper operation. SENSE- must be within 60mV of Vdd for proper operation. I think I can manage this by: a. wiring Vdd to the output of a voltage follower (Op Amp + connected to DUT power and Op Amp - connected to the Op Amp output) b. powering the Op Amp from the RedBoard c. using a MCP6002 rail-to-rail Op Amp. The MCP6002 maximum output voltage is Vdd-25mV so I should be able to satisfy the LTC4150's SENSE+ tolerance of being within 60mV of Vdd.

    Do these changes seem reasonable/doable/complete for what I want to do?

    One other thing. Member #1269246 didn't think the shutdown mode was useful. The datasheet states: /SHDN forces the LTC4150 into its low current consumption power-down mode and resets the part. I use the /SHDN signal so I can start a new test. I've found that the reset causes an interrupt about ~200mS after the reset. My code waits for that interrupt to begin the next test. My sketch has a watchdog so I don't get stuck waiting for the interrupt.

  • Is the skillet in this article an: Oster DuraCeramic 12" Square Electric Skillet in Black/Silver, CKSTSKFM12-ECO Link: http://www.target.com/p/oster-duraceramic-12-x-12-skillet/-/A-14674773 It looks like it might be. I ask because finding a skillet that goes to 450F(230C) is hard to find. Mostly because the product details don't often list the maximum temperature.

  • "Hookup Guide" link:

    https://learn.sparkfun.com/tutorials/femtobuck-constant-current-led-driver-hookup-guide-hi-power-version

    is broken.

  • Have the Mac users succeeded using this Multimeter? Member #686974, have you gotten any "sensible data out of it" yet?

No public wish lists :(