Dual Inline TDS Meter: where to place?

[reef_noob]

So, I'm planning on buying a dual inline tds meter for my new ro/di unit. What I was wondering is whether I'd be better off measuring before the water goes into the filter and after it leaves, or before and after the di stages.

It seems like measuring the output after ro but before di and after di give me the best measures. I know the approximate tds of my water, so measuring after the ro should give me a reasonable assessment of my ro membrane's performance. Then, measuring after the di will give me a reasonable assessment of the di resin's performance and also gives me the final tds of the filtered water (0ppm I hope)

Does this sound right?

[phiberop840]

that sounds like a great idea. I wish i had thought of that when i installed my rodi. I have mine before all goes in and after all comes out. still reads 0ppm.

Mike

[VWD]

the in on the line before all the filters and the output after the DI filter