I am using Arduino UNO, DHT 11, and ESP8266 WiFi module to measure temperature and humidity in a room every 15 seconds and sending it to ThingSpeak website for storage. I connected the Arduino to a 9V alkaline (from Amazon) battery to power my project.
What I want to know: I need to estimate how long will my project last with a single 9V battery hooked up to the Arduino board. I basically need an autonomous system to collect data.
What I researched so far: People on the web suggest breaking the circuit and measuring the current flowing through the circuit. Then knowing mAh of the battery, I can get a rough estimate of the running time.
What I need help with: Can I actually do what is suggested above? If so, where exactly do I break the circuit? If not, what other techniques can be used to estimate the time?
*** I am looking for a detailed answer here. I am new to Arduino and trying to learn as much as I can.
*** I have included a picture of my circuit and a multimeter that I have on hands.
An update: This is just a test project. For those of you suggesting how to approach things - the actual project is to monitor the weight (later on volume as well) of a compost bin and send that data to a server. So if you have suggestions about load sensors, I am all ears. Thank you.