Hi all,
i am very new to this so i hope i haven't posted in the wrong place.
I have a small circuit designed using a PIC10F200 microchip which control LEDs flashing and the data sheet of the microchips says that it should use 100 nano amps whilst in sleep mode, however it seems to be using significantly more than this. I have looked for meters that are capable of measuring nano amps but they priced at around $10,000USD each. Can anybody suggest a simple circuit i could build that would allow me to measure the current of round 100 nano amps.
Christopher
No on prop $10,000 USD!
I have in my hands a button cell, a 1MOhm resistor, and an average run of the mill $10 DMM. In simple series circuit I drop the science:
I = V / R
3.089amps (calculated) = 3.07v(measured) / 994kOhm(measured)
My current measured is 3.1 microamps, very close to the calculation. A $50 meter, clean contacts of probes and test points could produce a needless better result. As you see the meter measured down to 0.1 microamps. This is equal to 100 nanoamps. So my $10 meter can measure current in steps of 100 nanoamps at its lowest current measurement setting. You do not need a $10,000 or any other outside the standard issue DMM.
You do need to try test and experiments on your own. Read up on DMM spec where you will see the sensitivity of the device. Study the datasheet for whatever microcontroller of desire. It always states what the real sleeping currents will be based on peripherals enabled, voltages applied, and clocking speed. The greater the number of peripherals turned on during sleep the greater the increased deviation from the lowest possible sleep current. The greater the voltage applied, the greater the.... you know the story.
Using nothing outside the pins attached to the silicon package to measure sleeping current first. This verifies the device. After which, slowly add components and graph the results. If leaky caps, voltage dividers, pull-ups or pull-downs are in the original test, you will have no clue to who is the culprit sucking up power.