[MWJB]

@MWJBone more question: I calibrated using distilled water, reading 0.00. Then I measured regular tap water and also got reading 0.00 - is this malfunction? For coffee -espresso- I got pretty good reading, around 21%.

Is there any solution against which I can test? I mean XY gramm of sugar to XY gramm water should be read XY value.

EY varies with origin, amongst other things. Ethiopians, Kenyans, Colombians might be fine at 21%, Brazil, Guatamala, Costa Rica might be lower and still taste good. A ~4% span, averaging accross all origins, is normal.

What TDS is your tap water (the one thing about tap water, is that there's no such thing as "regular")? If you live in a soft water area, I guess this could be possible.

We use distilled water to calibrate because the refractive index of distilled water is a known. I just calibrated the VST & Amtast with distilled & read tap water (312) on a conductive TDS meter and it read 0.04 on the VST.

It read 0.07-9 on the Amtast in native mode, 0.07 in TDS mode.

None of this means very much. Tap water is way out of the typical range that espresso, or even filter coffee inhabits.

 

[madrian]

"We use distilled water to calibrate because the refractive index of distilled water is a known. I just calibrated the VST & Amtast with distilled & read tap water (312) on a conductive TDS meter and it read 0.04 on the VST.

It read 0.07-9 on the Amtast in native mode, 0.07 in TDS mode. "

I feel so dumb. In Amazon's description is 0.00 resolution for this cheap meter, but in real life the resolution is 0.0. This is why I am getting 0.0 for distilled & tap water (if difference is in the 0.00 range).

Now I am thinking if I should return it or keep it.

 

[MWJB]

"We use distilled water to calibrate because the refractive index of distilled water is a known. I just calibrated the VST & Amtast with distilled & read tap water (312) on a conductive TDS meter and it read 0.04 on the VST.

It read 0.07-9 on the Amtast in native mode, 0.07 in TDS mode. "

I feel so dumb. In Amazon's description is 0.00 resolution for this cheap meter, but in real life the resolution is 0.0. This is why I am getting 0.0 for distilled & tap water (if difference is in the 0.00 range).

Now I am thinking if I should return it or keep it.

If you like short shots of espresso, like 1:2. then the error margin in EY decreases.

Even if you get the Amtast with a 2nd decimal place, you're going to get a big spread with brewed coffee.

 

[Zephyp]

What is the simplest way to accurately measure TDS for filter coffee with a refractometer? When I first bought mine I followed some website I found, which used alcohol wipes and pipettes.

Today I tried simplifying it, but I don't know if that affects the accuracy or chances of inaccurate measurements.

The VST was clean and I added DI water with a clean metal spoon to zero it (how often is this necessary?). Then I soaked up the DI water with paper towels before wiping the sensor area with a lint free cloth (wine glass dish towel). Next came the coffee, added with another clean spoon, allowed to cool for a minute before taking the measurements. After that I soaked up the coffee with paper towels, added som DI water to do circular sweeps with another piece of paper towel before ending with circular sweeps with the wine towel.

Can this method lead to bad readings? Anyone got a better way to do it, preferably without more tools than necessary and ideally something I already got in the kitchen? I'd prefer not using pipettes or alcohol wipes, but I also want good measurements, so I don't want to make them a lottery just to make the process simpler.

 

[MWJB]

Can this method lead to bad readings? Anyone got a better way to do it, preferably without more tools than necessary and ideally something I already got in the kitchen? I'd prefer not using pipettes or alcohol wipes, but I also want good measurements, so I don't want to make them a lottery just to make the process simpler.

As long as you are consistent with the amount of coffee placed in the VST, I don't see an issue. 0.3ml gives me about a 2mm halo around the sensor.

You will probably need to use alcohol, at least occasionally if you have trouble setting zero. You don't necessarily need alcohol wipes, you can buy a bottle of isopropyl alcohol & use lint free cloth/paper wipes.

I don't mind using pipettes, I have a few in rotation at any one time, flush them & then dry them.

Are you getting wildly irregular readings?

 

[Zephyp]

As long as you are consistent with the amount of coffee placed in the VST, I don't see an issue. 0.3ml gives me about a 2mm halo around the sensor.

You will probably need to use alcohol, at least occasionally if you have trouble setting zero. You don't necessarily need alcohol wipes, you can buy a bottle of isopropyl alcohol & use lint free cloth/paper wipes.

I don't mind using pipettes, I have a few in rotation at any one time, flush them & then dry them.

Are you getting wildly irregular readings?

I have wondered if the amount matters. I haven't measured it, but try to use about the same amount. Easier with a pipette than spoon perhaps. I'll keep that in mind.

I got a bottle with isopropyl.

Not yet, I just started doing readings like this. Just wanted to check before doing a bunch of them. I suppose I'll see when I keep measuring similar brews how consistent it is. Thanks.