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June 20, 2015
Tutorial - LTC4150 Coulomb Counter Hookup Guide
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:
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.
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?)
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.
Tutorial - Reflow Skillet
about 4 years ago
Is the skillet in this article an:
Oster DuraCeramic 12" Square Electric Skillet in Black/Silver, CKSTSKFM12-ECO
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.
about 4 years ago
"Hookup Guide" link:
about 5 years ago
Have the Mac users succeeded using this Multimeter? Member #686974, have you gotten any "sensible data out of it" yet?
No public wish lists :(