Sharing of Pop Science Grade Review! Xiaomi Mi TDS Pen Water Quality Tester!

I bought Xiaomi Mi TDS pen around 2015, I think from the user point of view, I am “experienced” and able to comment on this,  (suggestion given by thread starter is base on relevant information that I got, and this is mainly my personal opinion.)

Xiaomi TDS pen is measured the conductivity substance in the water and then converted it into a digital number for people to see, but the Mi TDS pen itself is unable to detect bacteria, viruses and other substances. To put it simply, when the TDS value is large, indicating that concentration in the water is high and the water quality is probably not good or contaminated. The low TDS value indicates that the concentration is low and the probability of pollution is lower. Therefore, TDS measurement only gives you an idea of the total dissolved solids in the water, and can not tell you exactly what is the material is, whether it is good or bad.

Knowledge point to add: Xiaomi TDS pen is sensitive to temperature, the higher the water temperature, the TDS value will become larger too. So the measurement will take times for the temperature display by the tester similar to the water temperature to ensure the accuracy of the measurement. 

We need to make it clear here: Xiaomi Mi TDS pen is not the gold standard test for water quality! It is just a convenient way for us to determine the water quality preliminary. It can give you a warning when unexpected water pollution occurs.

Therefore, we do not need delusional or derogatory with malicious intends to Mi TDS pen, we should assess the usefulness of Xiaomi water tester in our daily lives and see whether it is necessary. (PS: Besides measure water quality, Xiaomi Mi TDS pen can use in many other ways and I will show you later in this review)  Get it the cheapest here!

Next is the unofficial unboxing review


I did not throw the packaging box, not because I am a crazy collector but I need this box to keep the pen after use. After all Mi TDS pen is used for measure water quality, I would like to keep it in the clean place after use. The packaging box (= storage box) is an easy and convenient way to keep the Xiao pen. Although it is making with paper, it quite durable and only slightly dirty after some time but still look good overall.


There is basic information, manual and how to read the TDS value listed at the back of the packaging box,  this is one of the reasons I keep the packaging box. It makes the box useful and easy for me to check the information.


Just pull out like a pencil box, it not only increase the usability, but easy to use and keep, the first few pictures look like a used goods, after all, it used more than two years, but inside the box still look new.


When you take out the Xiaomi Mi TDS pen, I think it is as new as a new pen.


Mi logo at the bottom, Xiaomi is already a guarantee of domestic quality, I am confident with it.


TDS button, in fact it is the power button.


Display screen although not shown in color, but it is only a gimmick to put color display screen on this Xiaomi Mi TDS pen.


Test section is protected by a cap, color between cap and the test section is different but look natural, easy to distinguish


At first, I habitually want to cap it like a pencil at the top of the Xiaomi TDS pen, but it does not match, so you need to keep the cap well to prevent it missing. Luckily, the test time is usually very short, a careless man like me also did not lose the cap.


A close look at the core monitoring unit after removing the protective cap, you only need to swing the Xiaomi TDS pen after use to get rid the water and the core monitoring unit will become clean again.


The test method, the use of the Xiaomi water tester is very simple: press the TDS button, insert the tester into the water, waiting for the display to show the value.


1.Before insert into the water, switch on the Mi TDS pen and check whether the display value is 0, under normal circumstances it should be 0, if not, we must see if there is water or malfunction (to do any test, we need to ensure that the test tool is normal, Clinical medical monitoring equipment need to do quality control every day).

2. Like what I mention beginning of the review, the temperature has a great influence on the test structure, so you must not test on the boiling water but need to wait it become cold water, you should check the temperature.

About durability:

I have never replaced the battery since I bought the Xiaomi TDS pen and it still can normal operate!!!

Following is the main content for this review, other uses of  Xiaomi Mi TDS pen : (thread starter gather some of the online information relate with this and do an objective integration analysis, this merely represent personal opinion) 

First, testing the authenticity of cosmetics

A lot of female users are very concerned about the authenticity of the cosmetic bought from Taobao and through daigou(a freelance retail consultant). This method is actually useful, but just like how it measures the water quality, it just assists you to determine the authenticity but not directly tell you the answer.

This belongs to my wife, since the combined contents inside the high-end cosmetics, toner almost the same, so you can use Xiaomi Mi TDS pen to measure the total dissolved solids, the deviation is not too large, indicating the high probability of this bottle is authentic one. 

There are few netizens do a test on brand new SKII Facial Treatment Essence, and the Mi TDS test result is 640, 678, 659 respectively, the value is very close.(Picture obtain from internet, no logo)



If this test method is popular, businesses owner can add or subtract the relevant substance to meet the corresponding TDS value, so that to test the authenticity of cosmetics with Xiaomi Mi TDS pen is useful but it merely just for your reference. Somehow you can use it in certain context like you buy two similar cosmetic products from two different people and you found out the Mi TDS test result is significantly different, then you know that something must be wrong. 

Second, Test on pesticide residues in food

Test the water quality with Xiaomi TDS pen before cleaning the food as a baseline(without any detergent, water cleaning only), if the TDS value increased significantly after cleaning the food, it is possible that excessive pesticides, of course, this is merely a reference and we don’t want you to see this as a gold standard and totally do not believe to the safety of the food you eat.


This is value of the water quality tested by my mother before washing vegetables (my mom like add vinegar, learned it through WeChat), the value is 308.



This is after washing the Chinese cabbage, the value is 317, so in general, I feel ok, my mom comments that may be the current weather is cold so the vegetables are clean also.

Third, good news for people who fish keeping at home, it can remind you when to change the water.



The theory is very simple, I just change water for my turtle and fish, so TDS value should be relatively low, but after a period of time, because of  metabolism, the concentration in the water gets high, and the TDS value was significantly increased, then you know that this is a time to change the water, or the water will become harmful to your little pet. Since my Xiaomi Mi TDS pen is mainly used for monitoring drinking water, please excuse me for skipping this part. 

Fourth, use your divergent thinking, this is really not just a pen to measure water quality

Through the previous example, we can know that by using Xiaomi TDS pen we can measure total dissolved solids in the water and get a TDS value, by the change of the TDS value, we can determine what changes in the water quality. To make it clear, let me show you few more example 

4.1 Hand washing clothes before testing TDS value of tap water, and repeat the test to check the TDS value after washing the clothes to see whether you have to get rid of all the suds.

4.2 Swimming at the swimming pool, before jump into the pool, do a test on water quality and redo it after you get out of the pool. By doing this, you can know whether the businesses owner uses some water recycle devices to prevent the cross infection. 

Well, return to the topic. Do you need it,  how is usability?

In this fast-paced society, just like eating “fast food”  many people like to see the conclusion when reading the post. Well, to satisfy all the spectators, I will give my conclusion first :

Whether you want to buy or if you already have a water purifier, or if you care about water purifying issues, I’d recommend buying one for the emergency. 

Reason for purchase:

If you encounter the circumstances like I mentioned above, you really need to buy one, but in other cases like below I do advise you to buy one because : 
1. Xiaomi Mi TDS pen is easy to carry, whether you travel or business trip, like you need to visit someplace which you lack the confidence to their water quality or when you hotels offer direct drinking water,  you can test the water quality before drink it.

2.Cheap and Xiaomi is brand guarantee, you can rest assured when buying

3.Although the water purifier can measure the water quality, it limited in fixed location 

4.Beside measuring water quality, Xiaomi TDS pen can use in many others way, you can use your creativity to find it.

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