An inexpensive and pretty decent pulse oximeter

A while ago, I came across a review of a relatively simple pulse oximeter and thought, why don’t I have one yet? So I ordered one.
A brief look at my purchase and a few conclusions.

As usual, a reminder: to keep up with new posts on the blog, I recommend following me on Instagram, where I’ll post notifications about every new article and maybe write about something interesting now and then — link to my account

The review was really just the nudge I needed, because I almost immediately found a slightly cheaper option and bought it there. The page has several different versions; I bought the first listing — With PI.
I also figured it was inexpensive and could even come in handy in the current circumstances. It can sit at home just in case, much like a thermometer.

A while later, I picked up an envelope from the post office. Inside was a box with the pulse oximeter’s technical specifications, along with some general information.


There was also a manual, but I’ll say up front that it had little to do with the actual device: the settings menu only partly matched, so the manual wasn’t much use.


The device is fairly bulky, about the size of two matchboxes. Interestingly, it even has little feet on the bottom cover :)


It opens like a clothespin. Inside, there’s a soft, rubber-like material, as well as a sensor and an emitter that glows red during operation. The LED is at the top, and the sensor is at the bottom.


It runs on two AAA batteries, but as users have already pointed out, the contacts are identical for both the positive and negative terminals, so it’s very easy to insert the batteries the wrong way around. Be careful and follow the markings.


The display is easy to read, but it washes out in bright light. It’s fine under normal room lighting, but in sunlight or under a flash, you can’t see anything.


I tried taking photos without the flash, but it’s difficult.
If you simply turn the device on, the screen shows dashes and a message saying the finger has been removed. After about 8–10 seconds without data, the device switches off automatically. The same happens if you just take it off your finger, so there’s no power button—and none is needed.

The screen displays:
1. Blood oxygen saturation as a percentage. I think this one is self-explanatory.
2. Battery charge
3. Perfusion index (PI, pulse modulation index), a measure of blood flow. I read the description, but still don’t fully understand what it tells me, since the readings often fluctuate over a wide range.
4. Pulse rate, which I think is also self-explanatory.
6. A bar graph showing the pulse over time.
7. The pulse scale at the bottom shows both the pulse itself and its amplitude, as I understand it. Overall, it’s only useful for checking whether the readings are being picked up properly.


I wanted to take it apart completely, but the clothespin mechanism isn’t easy to disassemble, so I decided to remove just the top part. Besides, the only thing I wouldn’t be able to see that way is the photosensor.

The side of the board facing the screen is covered with black film to make it look better. The board itself has some chip with its markings rubbed off, plus a few other small components.


When switched on, the device name—Oximeter—appears on the screen first, for some reason in a Gothic font :)
If you hold the button down for a few seconds after switching it on, you enter the settings mode. But the settings are a mess: they’re clearly intended for audible alerts when readings go beyond set limits, yet the photos above clearly show that the device has no buzzer.


I can check whether it works, but it’s hard to say how accurate the measurements are—I have nothing to compare it with.
But subjectively, everything seems fine. Here are three photos:
1. At rest.
2. I held my breath for a while, and the saturation gradually started to drop.
3. I walked briskly, and my pulse jumped right away.

Obviously, there’s some measurement error, but in my opinion, it’s more than accurate enough to tell “everything’s fine” from “something’s wrong,” and that’s all I need. By the way, it usually shows my saturation at 97–98%, sometimes dropping to 96%. I don’t think I’ve ever seen 99.


I can’t measure the parameters listed above, but I can certainly measure the current consumption.
I measured it in two modes: off and measuring. Those are the only modes the device has.

I got 40 µA when off and 16 mA when on. Here, I should put those figures in context by comparing them with typical batteries.
40 µA is about 1 mAh per day. An AAA battery has a capacity of about 500–1000 mAh, so even if you simply leave the device on a shelf, it will completely "eat" the batteries in 1.5–3 years.
16 mA means about 30–60 hours of continuous operation, depending on the quality of the batteries.

But as you can imagine, 30–60 hours is with fresh batteries; after a year, that figure will be noticeably lower.


My conclusions will be almost entirely subjective.
For the most part, I liked this little device. It’s inexpensive, seems to measure reasonably well, and is perfectly usable.
But the menu says one thing, the manual says another, and there’s no beeper. The most it can do to alert you is flash the relevant digits.
I still haven’t figured out whether I need this perfusion index, but then again, information never hurts—it might come in handy.

All in all, I don’t know whether to recommend it or not, but it works just fine for me, and my wife liked it too :)

That’s all for today. I hope this information was useful.