NP25 Current Consumption / ucurrent

[Harald]

(10-11-2015 05:25 PM)TomC Wrote:  Hello Harald:

Thanks for the prompt reply.

Agreed, this number seems very small -- I have verified this value.

I will try to post full test schematics soon; I have a uCurrent Gold current sensor in series with the 3 volt power supply. The output of the uCurrent device is connected to a HP3468 voltmeter and a Tek465 oscilloscope. The ucurrent may limit the response to 300kHz, but I do not believe this will be an issue with this design. The scope has 100MHz bandwidth, so I believe these measurements to be 'sound'. On the scope, one can observe the max current draw of about 1.2 mA with much (depending on what is displayed) of the time dropping to about 1/2 that amount (i.e. 600uA).

The design shows some interesting characteristics in that a full display [-8.8888888-88] actually draws LESS average current than with a single '1' in the display! I assume this is due to how the display is strobed. One would have to study the code to understand what is really happening here.

Also, the HP 'bubble' displays luminosity is specified at 1.0mA.

TomC

Hi Tom,

hmm, I don't quite understand why you would get those low measurements. Maybe the Hardware has changed?
I mesured on my NP25 just now and here is the screenshot:



As you can see at a constant 3V (measured on chanel 2) the peaks are just below 40mA and the average is 23mA. By the way, as the battery resistance isn't present, I lost one segment of the 8 leftmost digits. Probably due to the excessive current (not beeing limited by the battery).

I always wanted to do a redesign of the hardware - but as always, there are more projects than time to work on them