MSP430FR6043: Confirm if the 3-µA overall current consumption (Water flow measurement) is for 1 TOF only or more than one TOF (Time of flight)

Hi Jonathan,

let me rephrase it. The charge consumption per measurement is smaller than 3uAs (micro amp seconds). The measurement includes a complete upstream and downstream pules transmission, capture and math evaluation of the result. If you would like to have one complete measurement per second this translate into 3uA; for ten measurements per second to 30uA average current consumption. This is valid for typical transducers used in utility meters of regular size @ 1MHz. . A DN50 or DN100 pipe might allow larger transducers, or longer excitation time; for that you need more power.  

Also not included is the leakage current of the device or the real time clock module and it's 32kHz oscillator (those are required anyway to build a real meter). But strictly speaking they are not part of the measurement.

Now measuring that current is tricky due to its high dynamics... the peak current would go into some mA (depending on the chosen components). But those milliamps are only consumed for some hundred microseconds; then there is nothing for almost one second. Don't us a regular multi-meter to measure that you will fail.

Johann

Hi Johann,

Thank you for this response.
I forward this to our customer and comes up with this question:

If he has 1000mAh battery how long it will keep the ultrasonic metering system on(calculating dTOF)?

or

how much amperage the MCU will consume to do 1 dTOF and 3600 dTOF?

Thank you for your support.

Jonathan

Hi,

I'm making simple conservative assumptions...

- 1 measurement/s  => 3uA

- basic application. LPM3,LFXT32k,LCD, int bias,@25C (DS Tale 5.8) =>2 uA

- Radio => no radio, but LCD always on instead  =>3uA average current.

- 1000mAh /5uA => 200000h  => 8333d =>22.8a => 60% self discharge...

I would estimate 10 years unless you use a battery with real low self discharge.

for 8 measurement/s => 24uA+2uA => 26uA total consumption

- 1000mAh/26uA => 38461h => 1602d => 4.39a =>25% self discharge => 3+years

these are just rough estimates, have fun

   Johann