It is a first question to start.

1. Decide single chamber flow meter or differential (two chambers).
Most of diesel engines have supply and return line.
So, you need either measure fuel flow in both lines or modify fuel system in such manner, so there is only supply flow must be measured.

Easiest way - measure supply and return flow with Eurosens Delta flow meters. Eurosens Delta calculates total consumption based on supply and return flow.

If you want to save a little money - you can modify fuel system and install Eurosens Direct.

How to modify fuel system - look here:

It is important that modification of fuel system in such manner can affect operation of engine, expecially when engine have modern design (Common-rail, many electronic sensors).
We can recommend to do this modification only if:
1. Engine is not performing under maximum load
2. Engine is Euro-2  or older. Don't have a lot electronic sensors which can detect error
3. You have enough experience and knowledge in diesel engine operation and design.