Refractometer vs Hydrometer

[hkgar]

I read recently that a refractometer was necessary to get accurate readings and so since the Drs group had them on sale for about $40 I ordered one. I have been using a Hydrometer since I started about 3 years ago.
WOW
The Hydrometer reads 1.225 and the Refractometer reads 1.30 - a significant diference. If you don't have one, get one.

 

[gregm779]

I second that, never trust a hydrometer

 

[golfish]

Originally Posted by GregM779
I second that, never trust a hydrometer

unless its a glass floating hydrometer.

 

[buldog9]

I bought one a few weeks ago, do you know how to calibrate it? It says to drop distilled water and adjust until ` the light/dark boundary coincide with the water line`. I dont understand. I did adjust the line to zero, and when I tested a salt water sample, it read only 3 on a scale of 0 to 30. I cant translate that either.I`m not sure if this thing is calibrated right,or what. Can anyone advise,please?

 

[bergamer]

turn the eye piece a little, I had the same problem, in that I could not read it (atleast I thought I was reading it). But I realized that I could not understand it because the numbers were too small. If you twist the eye piece, it magnifies. Then it will all be clear!

 

[buldog9]

I can get a clear image, the problem is i`m not sure if i`m getting a correct reading, the seawater reads 3 on a scale of O-28 salinity, what does 3 mean? 3 percent?I know that my salt is at 1.021 or so [LFS test], when I test with floating hydrometer, it is right where its supposed to be, but when I test with refractometer, it reads 3... What the heck does that mean?Not calibrated? I tried to calibrate with distilled water, i was wondering if anyone knew how to calibrate, and what the correct reading SHOULD be on a Refracto. Thanks.

 

[gregm779]

There shouldn't really be a 3, look harder does it say 1.02 anywhere? When you calibrate it, it should be at zero then it should go up 1.020, 1.021, 1.022, 1.023.....

 

[buldog9]

No, the scale is from 0-28 with a % sign at bottom . At the top, at 28,it says saturation point. On the left, it says Salinity. On the right it says 20 deg. C. Thats the scale it has.

 

[f1shman]

well salinty is a different scale then specific gravity, look for a conversion chart online

 

[gregm779]

mine has salinity and sg. I'll compare for you
Salinity SG
30 1.023
35 1.027
40 1.030
You shouldn't keep your salinity at a 1.021 unless it's a FOWLR, I run mine around 1.027

 

[buldog9]

OK, thanks.

 

[f1shman]

Is the refracto from dr. nice? thats a great deal!!! Dr: $38.99 LFS: $150
god my LFS is a rip off

 

[hkgar]

Fishman,
I am really pleased with the Dr.'s refractometer. I figured I would never find one for that price, so when the sale came on I jumped. Even with shipping it was a good deal. Particularly if you add some other stuff to the order to reduce the per item shipping cost.

 

[hkgar]

Originally Posted by buldog9
I bought one a few weeks ago, do you know how to calibrate it? It says to drop distilled water and adjust until ` the light/dark boundary coincide with the water line`. I dont understand. I did adjust the line to zero, and when I tested a salt water sample, it read only 3 on a scale of 0 to 30. I cant translate that either.I`m not sure if this thing is calibrated right,or what. Can anyone advise,please?
I don't know for sure how yours works but with mine the calibration with distilled water was to get a reading of zero. Then when I test the saltwater on one side I have the specific gravity and on the other the PPT (SP is a scale that is 1.02.. to 1.04 or there abouts. The PPT is parts per thousand - Should be about 35. Don't accept that a certain SP equals a certain PPT as the PPT is tempurture dependant and will change at the even though the SP might not. Kind of like the air - the warmer it gets the more water the air can hold.
PPT is the most important reading. If you use a hydrometer you should have a tempurature conversion chart to get the correct ppt

 

[bergamer]

Originally Posted by buldog9
I can get a clear image, the problem is i`m not sure if i`m getting a correct reading, the seawater reads 3 on a scale of O-28 salinity, what does 3 mean? 3 percent?I know that my salt is at 1.021 or so [LFS test], when I test with floating hydrometer, it is right where its supposed to be, but when I test with refractometer, it reads 3... What the heck does that mean?Not calibrated? I tried to calibrate with distilled water, i was wondering if anyone knew how to calibrate, and what the correct reading SHOULD be on a Refracto. Thanks.

I am telling you I had the same problem, magnify the image by turning the eye piece and then everything will be clear. I thought I was seeining the same thing as you and after playing with it for a while, I accidently turned the eye piece too much and then it was very clear and very easy to use

 

[ophiura]

Originally Posted by buldog9
No, the scale is from 0-28 with a % sign at bottom . At the top, at 28,it says saturation point. On the left, it says Salinity. On the right it says 20 deg. C. Thats the scale it has.
Are you sure you have a salinity refractometer designed for this purpose? Because if that is the scale, then I reckon you don't have one designed for salinity (for this purpose). 28ppt isn't even the salinity of natural seawater.