I have a no-name TDS meter that I purchased from a local hydro shop, so I trust it to be accurate. But I had something weird happen today.
When I tested the pail for my biggest plant (wk 8 flower; Super lemon haze auto), my TDS displayed -19...minus nineteen! I don’t know if that was a measurement, or an error code. Sadly I don’t have a name or any documentation for it...well I did at one time, but it was all in Chinese.
What I decided to do was take water from another pail that was registering 800ppm and start mixing it with the water that was -19. Using a 4 liter measuring jug, I started by adding 1l of 800ppm h2o and equal part of the -19 h2o. This brought the TDS to -12. Interesting....so I added another liter of the -19 h2o into the mix. Now a reading of -6. One more liter of -19 h2o and the reading was 0. I decided to slowly add more to see what would happen. And after approx another 250 ml my TDS showed 822ppm.
The results made me think the negative # display was to show that the results were more than the 3 digit display could show. As though -19 meant 1900ppm because of the display limitation. To see if my theory was right, I made a measured amount of fresh nutes to 850ppm and slowly started to continue adding nutes. Once the TDS was at 999ppm the next increment was not what I expected. The display now showed 005ppm with “10x” displayed in the corner. Something I have not seen before. Now it makes the negative # display even more trivial.
Anybody know what’s happening? Is it even possible to have negative PPM?
When I tested the pail for my biggest plant (wk 8 flower; Super lemon haze auto), my TDS displayed -19...minus nineteen! I don’t know if that was a measurement, or an error code. Sadly I don’t have a name or any documentation for it...well I did at one time, but it was all in Chinese.
What I decided to do was take water from another pail that was registering 800ppm and start mixing it with the water that was -19. Using a 4 liter measuring jug, I started by adding 1l of 800ppm h2o and equal part of the -19 h2o. This brought the TDS to -12. Interesting....so I added another liter of the -19 h2o into the mix. Now a reading of -6. One more liter of -19 h2o and the reading was 0. I decided to slowly add more to see what would happen. And after approx another 250 ml my TDS showed 822ppm.
The results made me think the negative # display was to show that the results were more than the 3 digit display could show. As though -19 meant 1900ppm because of the display limitation. To see if my theory was right, I made a measured amount of fresh nutes to 850ppm and slowly started to continue adding nutes. Once the TDS was at 999ppm the next increment was not what I expected. The display now showed 005ppm with “10x” displayed in the corner. Something I have not seen before. Now it makes the negative # display even more trivial.
Anybody know what’s happening? Is it even possible to have negative PPM?
