What kind of measurement tools would you recommend for measuring the amount of energy consumption in a transceiver module to determine the communication costs. We need a precise measurement for our work. INA 219 is an option for measuring DC voltage, current and wattage using in a Raspberry Pi. I prefer other available options.
Hello Bardia,
Can you provide more info for the tranceiver in order to make sure the INA219 has the appropriate resolution?
It depends how accurately you want to measure. It's no use measuring the current to 0.1% when your supply voltage could vary by 5%. You need to measure both to a higher accuracy than you want in your result. The INA219 illustrated seems to use a user defined current sense resistor - so fundamentally it's measuring the voltage drop across a resistor. Hopefully it's sensitive enough that this drop won't upset whatever it's connected to. How accurate is its voltage measurement and how accurate is the current sense resistor?
Dear Tony
Thank you very much fir your reply. I will inform you as soon as possible.
Dear Bardia,
By looking at the datasheet of ESP8266 and Xbee Series 1, their operating current is in the range of 50 to 300 mA.
The INA219 you suggested can be used to measure the operating current of the transceiver with good accuracy since its resolution is 0.1 mA (if its maximum measuring current is set to 400 mA, see user manual: https://cdn-learn.adafruit.com/downloads/pdf/adafruit-ina219-current-sensor-breakout.pdf).
It is not necessary to measure the voltage of the transceiver since it will be constant at 3.3 V. However, if you wish to measure it, just use a resistor voltage divider and an ADC (like the ADS1015 or ADS1115) for interfacing to the Raspberry Pi.
Tip: if you place the current sense circuit (INA219) in series with the 3.3 V supply (i.e. between the 3.3 V supply and the transceiver), the voltage applied to the transceiver will be 30 mV lower (assuming a current of 300 mA) than 3.3 V. This is not a problem for the transceiver but it will cause a slight error in calculating the consumed energy. This can be solved by measuring the voltage right at the transceiver terminals (i.e. after the current sense circuit). If you want to avoid measuring the voltage at the transceiver terminals, you can use a 5 V source and a 3.3 V voltage regulator and place the current sense circuit at the input of the 3.3 V regulator in order to avoid the voltage drop due to the current sense circuit and keep the 3.3 V fixed.
Dr Florides' answer is very comprehensive. Just note that if you measure the current at the input to the voltage regulator and not the output, you will also be measuring any current drawn by the regulator - which shouldn't be large, though.
Thank you Tony for the supplementary comment.
Typical current values drawn by a regulator are lower than 100 uA which will not be a problem in Bardia's case.
Thank you Michalis and Tony for your answers.
Michalis Florides Tony Maine
Dear Bardia
I agree with the answers of Mr. Michalis and Mr.Tony.
Regards
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