TDS meter calibration.

[ironman187]

I just received a HM Digital DM-1 dual inline TDS meter. However, I'm having an issue calibrating it. There is only one potentiometer in the back and both sides measure 22 TDS different than eachother. In addition, I can adjust one to read 342TDS in my calibration fluid, pull it out, put it back in and it reads 5-10 TDS higher. Is there a method to this madness?

 

[Reef.]

I just received a HM Digital DM-1 dual inline TDS meter. However, I'm having an issue calibrating it. There is only one potentiometer in the back and both sides measure 22 TDS different than eachother. In addition, I can adjust one to read 342TDS in my calibration fluid, pull it out, put it back in and it reads 5-10 TDS higher. Is there a method to this madness?

Do you know you can only calibrate an inline meter when it’s in place, so for that reason it’s next to impossible to calibrate correctly, the fluid is therefore useless.

 

[ironman187]

Do you know you can only calibrate an inline meter when it’s in place, so for that reason it’s next to impossible to calibrate correctly, the fluid is therefore useless.

I had no idea...so basically I just fubarred the calibration on this thing.

 

[Reef.]

I had no idea...so basically I just fubarred the calibration on this thing.

I also use a TDS pen only cheap to buy from eBay, I check at the start when making water, if they match all good, if you have an inline after the membrane also, that is still useful as it gives you an indication if the TDS is creeping up.

 

[KStatefan]

I had no idea...so basically I just fubarred the calibration on this thing.

Here is the calibration procedure

https://www.filterwater.com/docs/hmdigital/hmdigital-dm1-calibration.pdf

 

[ironman187]

Here is the calibration procedure

https://www.filterwater.com/docs/hmdigital/hmdigital-dm1-calibration.pdf

Yeah, I followed that. The sensors being off by about 22 TDS from eachother is concerning. I suppose I could re-try calibration using a TDS meter pen as a reference and just offset my reading by 22TDS for pre-DI stage water.

 

[KStatefan]

Yeah, I followed that. The sensors being off by about 22 TDS from eachother is concerning. I suppose I could re-try calibration using a TDS meter pen as a reference and just offset my reading by 22TDS for pre-DI stage water.

I would get it replaced then.

 

[ironman187]

Before I do that, I'm going to install them and see if the readings are that far off from eachother when being tested correctly.

 

[Reef.]

Before I do that, I'm going to install them and see if the readings are that far off from eachother when being tested correctly.

good idea, post back if they are correct once I place, will be interesting to know.