Swingarm Hydrometers = Useless

reef_noob · 09-14-2005, 10:29 PM

Well, I finally got my refractometer and tested several different sets of water with both the hydrometer and refractometer.

The results:

DI water @ 1ppm tds

Hydrometer: no indication/0
Refractometer: 0

Nano tank(5.5 gal total vol):

Hydrometer: 1.025
Refractometer: 1.030

Main tank(65 gal total vol):

Hydrometer: 1.025
Refractometer: 1.030

I think the results speak for themselves.
Presuming that the refractometer is calibrated correctly(which it should be based on the DI reading,) the swingarm is useless.

Save your money and sanity.
Buy a refractometer.

capt2000 · 09-14-2005, 10:46 PM

they matched at zero and were consistant in other samples, which one is right?

VWD · 09-14-2005, 10:46 PM

thats right, one thing I notice it your TDS (DI water @ 1ppm tds) Getting close to change time on the DI cartridge, Ro you can go to 10 % of input TDS but RO/DI 1 or 2 ppm is max.They don't lst long.I don't know how many people change them that way. I try to.

capt2000 · 09-14-2005, 10:50 PM

you need to test the two against a given, known, contant. You can only show the difference this way

VWD · 09-14-2005, 10:52 PM

Ro thats right DI need to be 0

VWD · 09-14-2005, 10:54 PM

I have imput TDS at 250 ppm, My output with RO/DI 0 if I had no DI and only RO, 25ppm will be ok, But even with DI 1 or even 2 ppm is better then 250 ppm.

capt2000 · 09-14-2005, 10:57 PM

i was speaking of the salt readings. they are diferent but compared to what? which is right? compared to? not argueing the readings to swing arm .025 the refract .030 in two samples, it doesn't say which is properly calabrated especially if both show the same zero

VWD · 09-14-2005, 10:59 PM

Quote:

Originally Posted by capt2000

i was speaking of the salt readings. they are diferent but compared to what? which is right? compared to? not argueing the readings to swing arm .025 the refract .030 in two samples, it doesn't say which is properly calabrated especially if both show the same zero

Your right there, have to be calbrated. I see what You are saying.

JCox · 09-14-2005, 11:02 PM

Does it really matter if his 'test' RO/DI water has a TDS of 1? A refractometer is measuring salinity/SG, not TDS. As long as his RO/DI is reading a spot-on 1 on the refractometer, I would assume that he is calibrated correctly.

xaoss23 · 09-14-2005, 11:02 PM

very good catch capt2000...

capt2000 · 09-14-2005, 11:05 PM

its like two identical cars at a red light both read zero. A has tires at 25 psi B has tires at 35 psi. both show 60mph B is pulling away. A radar shows A at 57 and B at 62. radar is the control or given.

JCox · 09-14-2005, 11:08 PM

I still don't understand what TDS would have to do with a refractometer calibration. Case in point, I have a refractometer that came with 'ultra pure test water' that tests 0 on my refractometer. I have also tested plain old tap water, TDS ~110, and this also shows a spot-on 0 on my refractometer. Am I missing something?

reef_noob · 09-14-2005, 11:11 PM

I should've been a bit clearer: With the DI, the refractometer read 1.000
The swingarm can't go to 1.000. It drops below the bottom of the range, which is 1.012.

Capt, you are correct. Presuming that the swingarm reads 1.000 with the DI(which is not something we can reasonably presume), then there is no reason to suggest that the refractometer works better than the swingarm other than anecdotal evidence from others about the accuracy of refractometers over hydrometers.

However, given that the DI reads 1.000(edit: with the refractometer), we can safely reason that the refractometer is correctly calibrated. Thus it's either faulty from the factory, or the hydrometer is incorrect. Which seems more likely?

reef_noob · 09-14-2005, 11:12 PM

Quote:

Originally Posted by JCox

I still don't understand what TDS would have to do with a refractometer calibration. Case in point, I have a refractometer that came with 'ultra pure test water' that tests 0 on my refractometer. I have also tested plain old tap water, TDS ~110, and this also shows a spot-on 0 on my refractometer. Am I missing something?

No but the instructions suggested using distilled water to calibrate, DI was the closest I could come.

capt2000 · 09-14-2005, 11:15 PM

no, he was comparing two tools against the same thing without knowing which was right. I agree swing arms are inacurate, salt build up etc., but if your control is rodi at 0 then my last post makes sense