The Multimeter is used for reading multiple pieces of information in machines in the Thermal Expansion mod. This includes reading network saturation, conduit averages, the energy requested by a machine, and the amount of liquid in a Liquiduct.
Using the Multimeter
To read network saturation (how full the buffer is on a line of conduits), use the Multimeter on a conduit that is not an output.
To read the average output of an output conduit, simply use the Multimeter on an output conduit. This will start the monitoring process, you can then use it again to get the average (Doing so before 20 ticks will not skew results, and will tell you how many ticks were averaged).
The multimeter can also read the energy requested on any machine that accepts Buildcraft power (and implemented the proper API's). It will return the amount of power the machine is requesting at the EXACT tick that you use it. Note: This may be hard to understand as many machines (read: quarry) request many different amounts depending on what they are doing.
Reading a Liquiduct will return the liquid type, the total amount of liquid in the system, and the throughput of the system. The total amount that one liquiduct can hold varies by the liquid (1 liquiduct can hold far more steam than it can lava). If the liquid does not have a hardcoded capacity value, it defaults to 500 per liquiduct. The throughput shows how much liquid is moving through the system, not how much is actually in it. If there is no liquid inside the liquiduct, it will return "Liquid: Empty".