Conversion factor for conductivity of an aqueous solution I am not 100% sure if this is the right place to ask, but please point me in the right direction if not.
I am designing a conductivity meter, and when it comes to displaying the results in mS/cm or µS/cm, I also need to convert to EC. The first place I found was THIS website which seems great as it has all the units that I can convert here and there, no problem. This site states that 1EC is equal to 1µS/cm.
I had started to do most of my calculations based on the conversions from this website. However, when getting a reference calibration liquid, I noticed it was set to 2.76EC/2.8mS, which goes against what was stated in the website. I then found THIS website which shows 1EC as equal to 1mS/cm. I have now seen another place online (closed the tab and can't find it!) that also agrees with this.
Another website I have found HERE gives a bit more information on the conversion, and states that EC is measured in deciSiemens per meter (dS/m), and 1EC = 1dS/m, which would be 1mS/cm. Then later, it has a conversion thing at the bottom which has a statement saying:

Conversions:


1 deciSiemens per meter (dS/m) = 1 mmho/cm = 1
milliSiemens per cm (mS/cm) = 1000 microSiemens per cm (uS/cm) 1
mhos/cm = 1 S/cm = 1000 mS/cm


Electrical Conductivity units (EC's) IF
measured in uS/cm: 1 EC= 1uS/cm = 0.001 dS/m = 0.001 mS/cm = 1 mS/m


(Example 1.5 dS/m = 1.5 mS/cm = 1500 uS/cm = 1500 EC)

And surely that contradicts itself where it says 1EC = 1µS/cm, then the example after says that is not the case?
I just wanted to ask and be sure on this.... When converting, is 1EC equal to 1mS/cm, or 1µS/cm?
I think you have badly confused yourself by mixing the concept of a property of a solution with the units used to express this property.
Total dissolved solids (TDS) is a property of a solution. Theoretically, it can have any units kg/ kg of a solution, part per million, percentage, or whatever you like. However, people have standardized what they mean by TDS is usually mg solids/L of solution or even ppm.
In the same way, EC is electrical conductivity. It is a property of a solution. It can be expressed in units of microSiemens/cm or any multiple of it. EC itself is not a unit.