A question about Angular components. Can a component become a member of another component?

Let' s say I have a sensorReading component that looks like these green boxes. I only want 4 of them in app-component(default one). How can I create 4 of these inside app-component and access their properties and methods from app-component.ts script?

I can create 4 of them in app-component.html with ngFor but how can I access elements of these sensorReading components I created with ngFor? Members are sensorType, value and unit as you can see.

Angular’s NgFor + selenium = StaleElementReferenceException :(