[JandS]

How do you guys check the accuracy of your TDS meters?
I have 2 abd the new one is showing different tap and pure readings to the old one.
My suspicions are that the new one is wrong showing tap water at 063 when it used to be around 90 and pure at 009 whilst the old one shows 001 for pure.

[p1w1]

think daqua sell calibration fluid for them.

[JandS]

Out of stock...need some definite pure to test on...

[Marc Stock]

TDS is only an approximation calculation anyway.

Most accurate way to test water purity by way of conductivity is to read it in microsiemens.

Plus we are only really interested in water that reads a nill value in conductivity for cleaning.

Taking a TDS  reading in itself is meaningless, its only good for checking the efficiency of your membranes by comparison of two values before ro and after.

It doesn't matter if between two meters one reads 2ppm and the other reads 5ppm on the same sample of water, as long as you use the same meter for both before and after mesurements of your ro you can calculate the % efficiency which is why we use them.

[JandS]

Surely it matters if we need to see if we have 000ppm..............if one reads 200 and the other reads 500 that's the same efficiency but the ppm is too high even at 200.

[JandS]

Not using Ro using double Di.

[JandS]

And then I realise the new one I have is fake/faulty...there is no calibration screw at the back.
From a reputable supplier as well not flea bay or Amazon.

[Spruce]

And then I realise the new one I have is fake/faulty...there is no calibration screw at the back.
From a reputable supplier as well not flea bay or Amazon.

Could it be that its calibrated digitally rather than by a screw pot at the back of the meter?

[JandS]

It's reading wrong Spruce so how do I calibrate it if it won't calibrate itself.

[JandS]

Sorted...they're testing a new one for me and sending it out asap.

[Spruce]

It's reading wrong Spruce so how do I calibrate it if it won't calibrate itself.

I don't know what model you have, but there are a couple of YouTube videos showing how to program some testers digitally. I'm sure if you do a google search you will find an instruction manual for your particular tds meter.

Electronically, adjustments made using a screw pot are very out of date. Even in the days when VHS recorders were popular they had started to use digital channel adjustments rather than mechanical means; that was over 22 years ago. (I worked for Channel 5 as a video retuner in 1995.)

Provision has to be made for adjustments, so if there isn't a screw pot then it must have to be recalibrated digitally. Maybe you have to hold one of the buttons down for a longer preset period and then use the other button to adjust the reading; I don't know. But however its done, you need to calibrate it to a known tds.

One of the posters on the other forum suggested you do a google search and one of the threads found was on how to make your own testing fluid by dissolving 342 grams of pure salt into 1 liter of pure water.

For me I would take a container full of pure water and add some resin to it. I would stir that mixture to ensure that each solid in the water has been dissolved by the resin. I would then have to presume that the water is now '100%' pure. I would recalibrate my tds meter to zero and work from there. The reading could be slightly out further up the scale but I'm only interested in the first 20ppm because that's want I want to remove when I polish my water off after r/o with my resin.

.

[JandS]

Cheers for that Spruce.