The basic reason to use an external satellite tuning meter is that the signal meter deflection is immediate and there is no lag time for digital to analog conversion when trying to tune using a receiver. I personally prefer the old style analog meter versions and feel that they are more accurate than the newer digital displays. The analog method is much more accurate and provides the best overall signal gain when used properly. I know installers, who have been in the business since the big dish era and still rely on the inexpensive types and know that if they fill with water or get dropped, then it is easy to hook up another, and isn't quite so hard on the pocket book.  I would put the analog meters into 2 basic categories: The first, requiring the voltage from the receiver to power both the meter as well as the lnb. These are smaller and have some real advantages when hanging from a ladder up high where you need another hand just to hang on.  This type will work just fine for tuning a single satellite or lnbf, but does have some draw backs if there are questions about signal, or there is something that might obstruct the incoming signal.  The second type that has a self contained power supply, can power the dish and lnb without any physical hookup to receiver.  This has obvious advantages for those that want fast reliable reads. The 2 types of meters I use are shown below. The channel master may be purchased under another name or manufacturer and perform the same functions. I like testing both outputs of the Dish Pro lnb for performance testing before hooking up to a receiver.  Typically 110 (EchoStar 8,10) is about 10 per cent lower than 119 (EchoStar 7) - Nothing beats the portability of the smaller signal meter which also has a 22 khz tone indicator made for Directv, but also works equally well with DishNetwork installations.  I guess, there could be arguments for the LCD display types but my eyes do not focus well looking at rectangular blocks in a rain storm, which happens more often than not in the Portland Oregon area.

Satellite Tuning:  Start with a short cable through arm to lnb and other to satellite meter (lnb side) and hook up the receiver cable at meter allowing enough cable to allow you to pull the receiver cable thru to lnb -Tighten lnbf as normal -  When tuning a satellite (whether single or dual) adjust the azimuth 2-7/16" nuts (dish mount on pipe) so that they are firm but still move freely on the mount.  The same with your 2-7/16" nuts for the elevation.(one on each side)  tight enough so that they do not slip with the dish weight. I tweek both directions for maximum signal and then rely on the receiver to verify that you are on the correct satellites, typically using a switch test ( DishNetwork) in receiver menu. When you are satisfied that signal is at maximum, then tighten nuts for both and not forgetting about the pipe mount nuts at the base of the tube support bracket, and upper dish mount nut.  Now, with everything tightened, try grabbing the outer edge of dish on both sides and apply a little pressure.  The meter should drop all directions - If the meter increases, then it isn't quite there yet. Repeat process to determine if elevation or azimuth adjustments are needed? Typically the signal will increase slightly after meter is removed from the line, so expect slightly higher results at receiver.