If you own an Apex FMM Module then you can buy the flowmeter sensors off ebay and make a DIY cable to hook it to the FMM.  It is a much cheaper alternative to buying the fmm flowmeters.

Supplies you need:
YF-S201 1/2" Flowmeter  - Ebay $4 
4 pole aux cord - Ebay $1
3pin female and male connector - Ebay (10pairs)  $3  
Heat shrink - Ebay $1 (I'm not exactly sure what size)
1/2" female thread to 1/2" barb - Home Depot  (2 pieces) $2

​

Tools
Soldering Gun
Wire strippers
Multimeter

Cut the end of the aux cord off and strip the wires back.  You will need to use a multimeter to check for continuity from the aux plug end to the wires you stripped to find out which ring on the pole goes to which color wire. The 2 aux cords I had were wired differently. 

​

​

​

​

​

​

​

​

​

My Aux cord colors 
1.Ground - Green
2.Power - Yellow
3.Red
4.Signal -Blue

Most likely the wire colors on the 3pin connector will be different colors then your flowmeter so you will have to plug them together and take note of the colors before proceeding

The flowmeter colors are as follows
Black - Ground
Yellow - Signal
Red - Power

You will want to wire to the aux cord like this
1.(Base of aux pole) Ground - Black
2.(second ring) Power - Red 
3.(third ring) Not used 
4. (Tip of aux pole) Signal - Yellow 

​

I matched (the colors might be different on your wires)
1.Black-Green
2.Red-Yellow
3.Yellow-Blue

​

​

​

​

​

​

​

​

​

​

​

​

 

Connect the cooresponding wires together Solder them together then test for continuity to make sure you got a good connection, if you do then heat shrink each wire.  When that is done put another larger heat shrink over the group of wires.

​

​

 

 

​

​

​

​

​

​

​

​

 

 

 

Now plug the finished cable into the flowmeter and the aux end in to the fmm. You will need to go to the Module Configure screen in the Apex and set the size of the Flowmeter