Ok,
EC=Electrical Conductivity of a liquid.
Pure water (distilled) has no EC but when you add impurities (Nutrients in this case) they conduct electricity, which ca n then be measured with a meter.
EC is measured in MS (millisiemens per Centimeter)
1 EC = 0.1MS
Cf=Conductivity Factor. Which is 10 times the value of the MS value.
ie, MS 0.1 = CF 1, MS 0.2 = CF 2 etc.
PPM = Parts Per million. Your meter takes a reading in EC/CF and then converts to a PPM reading which in your case is 1800.
Now this is the tricky bit
The scale used to convert the EC/CF to PPM depends on who makes your meter. I use Hanna meters and the scale for them is 1.0ms=500ppm or 10 CF
The problem is that with my meter a ppm value of 1000 is say 2.0 ms or 20 cf whereas with a different meter the ppm may be as much as 1400. There is a big difference there which is why it is better to measure in EC to calculate the overall strength of a nutrient solution.
If you let me know what meter you have I will show you an easy way to find the EC from ppm if the essay above is confusing
See I would say a ppm of 1800 is way too high as my meter would read an EC value of 3.6MS or 36CF.
Anyway I'm off for a little lie down now my brain hurts