Lucas Formula and TDS/PPM meter question, HELP!

[smknfire]

Just switched to Lucas formula 0-8-16 in rockwool after many sucessful runs with H&G in a UC. I know the target ppm in RO water is 1300ppm but i'm not sure what setting to have my meter on. It is a HM COM-100 and has the following settings:

Switching EC Modes:
The COM-100 has three different modes for EC: KCl, 442TM, and NaCl. Note that this setting only changes
the ATC coefficient that is used. To change the EC mode:
1. Turn the meter on by pressing the ‘ON/OFF’ button.
2. Press and hold the ‘HOLD/MODE’ button. The meter will cycle through the
following modes:
a. EC – KCl
b. EC – 442TM
c. EC – NaCl
d. TDS – KCl
e. TDS - 442TM
f. TDS - NaCl
3. When the meter displays the desired selection. Release the ‘HOLD/MODE’ button.
4. The meter is now ready for use in your selected mode. The meter will keep this setting until
changed again.
Switching TDS Modes:
The COM-100 comes with three TDS modes, each with its own EC to TDS conversion factor and Automatic
Temperature Compensation coefficient. To change the TDS mode:
1. Turn the meter on by pressing the ‘ON/OFF’ button.
2. Press and hold the ‘HOLD/MODE’ button. The meter will cycle through the
following modes:
a. EC – KCl
b. EC – 442TM
c. EC – NaCl
d. TDS – KCl
e. TDS - 442TM
f. TDS - NaCl

That is pulled from the manual.

thanks!

smknfire

 

[Hydrolized]

On the NaCl scale lucas is 947ppm.

If your really set on using ppm then use NaCl, its a .5 conversion factor. I would use the EC setting instead, it eliminates a lot of confusion when coming on here and telling us your numbers. Lucas EC should be around 1.95

 

[smknfire]

OK im starting to understand having my meter set on EC .7 conversion reads out at about 2000. I was just thrown off by this high of a reading, essentially 2.0EC right?

 

[Hydrolized]

Like I said that's why using EC and only EC is the best way to not confuse yourself or those helping you. 2.0EC is 1400ppm @ .7 2000ppm @.7 is 2.85EC.