Current does not change with voltage


I powered the data logger using wavecom modem with a external power supply. I measured the power supply current at different supply voltages: 3.9V, 3.7V and 3.5V. The resulting supply currents are about the same. Intuitively think the higher voltage should result in higher output current, but the results say differently. Don’t know why. Any idea? Thanks for your comments.



What datalogger?

What Wavecom modem?

To most observers, I think that 3.9V, 3.7V and 3.5V could equally be considered “about the same voltage”

If the power remains the same, then a higher voltage would result in a lower current!

What exactly is your problem with the readings?
Unless they are outside the specified limits, where’s the problem?

Remember that the current drawn by any GSM unit is very “peaky” - so any reading on a simple ammeter can only ever be a rough average…


I can’t release its name; it does not belong to me. Sorry about that.


Yes, I agree with you to a certain degree. The logger is powered by a battery which full voltage is 3.9V and it will fail when the voltage falls below 3.5V. You can see that for this logger, its full operation range is 0.4V, so 3.9V is much more significant than 3.5V for the specific logger.

Yeah, I agree with you. I am using a programmer DC power supply which provides voltage and current readings every 1 second. Compared with the GSM time slot (577us), 1 second is very long.