Nonin Oximeter Review - Onyx 9500 and GO2

Oximeter review: Nonin and Choice


Nonin Oximeter Review

Nonin Onyx 9500 pulse oximeter has been very popular on the market for quite a few years and then Nonin later introduced a new lower price model GO2 Achieve to compete with newer models introduced later by other new companies. These new entries are significantly cheaper than those from Nonin (as much as 50-70%). We have served thousands of customers and sold thousands of pulse oximeters. The same question keeps popping up - "are these oximeters as good as the name brand ones." We know that our products are solid based on our own testing and customer feedback; however we do not know how good they are when compared with Nonin Onyx 9500 or Nonin GO2. Which one is the best pulse oximeter?

We have designed multiple experiments and asked an independent testing lab to perform the experiments for us. We will push the oximeters far beyond their normal operating ranges. Remember that a bad reading at outside normal operating range does not mean the oximeter is bad. We would report the results as they become available.


We have just received the final report from the testing lab and completed the last article in the series. The whole exercise is a learning experience for us. In general, both Choice and Nonin oximeters worked equally well in all cases except under two conditions - very low blood perfusion (signal strength) and motion.

In one low signal strength test, Onyx 9500 passed all levels, while GO2, MD300C1 and MD300C63 failed to show any reading when signal strengths were at 0.1%, 0.2% and 0.3% respectively. Signal strength for a normal healthy adult is around 5%-6% level; 0.3% signal strength is very low.

The motion test was inconclusive; however the Nonin oximeters appeared to have an edge.

According to our research, Masimo pulse oximeters have outstanding record in very low perfusion and motion situations.

Of all the oximeters, only MD300C63 displays the plethysmograph, which provides important information related to your blood flow. We consider this to be a big plus.

The experiment was conducted on ONE oximeter from each model. The sample size is way too small to make any general statements; however the experiment does give us a glimpse into the performance of these four particular oximeters.


We selected four different oximeters for the study: Nonin Onyx 9500, Nonin GO2 Achieve, Choice MD300C1 and Choice MD300C63. The Nonin oximeters are purchased for $200 and $100 respectively from an internet store; we obtained the Choice oximeters from our inventory and they are listing at $65 and $109 at the time of this writing. MD300C1 is our most popular model and MD300C63 is the newest model from Choice. BIOTEK Index SpO2 Simulator would be used to perform the test. The simulator has an artificial finger to simulate a patient's finger. The simulator can simulate many clinical conditions, such as high pulse rate, poor blood circulation, low Sp02 saturation, motion... BIOTEX Index is a standard tool for testing pulse oximeters. These four oximeters were sent to the testing lab for the experiments (the simulator is an expensive equipment and we cannot afford to purchase one).


We are not testing for the accuracy of individual oximeters as this would require arterial blood samples with SaO2 measured using a laboratory co-oximeter. The cost will be prohibitive and our sample size would be too small to draw any conclusion. Our objective is to compare them. Furthermore, the BIOTEK simulator is not designed for testing accuracy.


The following diagram shows the picture for the four oximeters: Nonin Onyx 9500, Choice MD300C63, Nonin GO2, and Choice MD300C1.

Nonin and Choice pulse oximeters

The experiments consist of the following components:

  1. Appearance: Examine the construction and external appearance
  2. Usability:
  3. Specifications:
  4. Normal environment: Run a series of tests under some typical clinical conditions, such as weak pulse, bradycardia, neonate, and obese conditions. These are preset patient conditions defined in the BIOTEK SpO2 simulator.
  5. Signal strength (blood perfusion): Start with several initial settings, vary the signal strength down to zero.
  6. Pulse rate: Start with several initial settings, vary the pulse rate.
  7. Oxygen saturation: Start with several initial settings, vary the SpO2 level.
  8. Transmission level control (finger thickness): Vary the control through the entire range supported by the simulator.
  9. Light: Run the tests under various lighting conditions supported by the simulator.

These tests would simulate conditions beyond the operating range specified by the manufacturers; however we still would like to see how they perform under extreme conditions.

We are not testing for the accuracy of individual oximeters as this would require sampled arterial blood Sao2 measured using a laboratory co-oximeter. The cost will be prohibitive and our sample size would be too small to draw any conclusion. Our objective is to compare them.


All four oximeters are very well constructed and would last a long time with proper care. They are small and compact to the point that differences in size and weight are not factors any more. Onyx 9500 and MD300C63 appear to be slightly sturdier than the other two; we have not performed a drop test to confirm this. Choice has claimed that MD300C63 was designed for rugged environment.


Pulse oximeters are simple devices. One clips an oximeter onto the finger and obtains the reading in a few seconds. Taking a measurement is ease.

MD300C63 also displays a pleth waveform that shows the change in blood volume in each heart beat and generally reflects the patient's cardiac condition and the state of blood perfusion. It is especially useful for patients with heart conditions. Nonin oximeters and MD3001 do not have this function.

Both Choice oximeters can display a pulse bar graph and they are missing in the Nonin oximeters.

The two Nonin oximeters have sensors to detect the presence of fingers; they would start taking a reading as soon as a finger is inserted. For the Choice oximeters, one has to push the on/off button to start the reading.

The displays for the Nonin and Choice oximeters are big and bright. I have no problems reading them even without my glasses. MD300C63 has an edge here. It has dual-color OLED display which gives higher resolution and contrast. MD300C63 also has 6 display modes and can display the result in all four directions so you do not have to read the display upside down.


  1. Paul Batchelder and Dena Raley, "Maximizing the Laboratory Setting for Testing Devices and Understanding Statistical Output in Pulse Oximeter", International Anesthesia Research Society, Vol. 105, No. 8, August 2007.