|Product Performed to Expectations:||9|
|Specifications were sufficient to design with:||8|
|Demo Software was of good quality:||8|
|Product was easy to use:||7|
|Support materials were available:||10|
|The price to performance ratio was good:||10|
|TotalScore:||52 / 60|
MAX30001EVSYS Road Test Review:
1) Evaluation System Software: Installation was not seamless (Windows 8.1: Never successful on driver install. Windows XP: Installed but not without manual intervention for driver and .NET Framework. Windows 7: Installed with manual install of .NET Framework). There was no documentation of the software so it was somewhat of a trial and error process. This was not really any problem as once you play with the software (as well as review the data sheet) things become fairly straight forward. The software was well written and supports many features that make a designer's life easier.
2) Hardware Platform: Following the tutorial video on the Maxim Website provided a nice accelerator to get the board up and running. It would be nice if documentation for the board (i.e Schematics and PWB Layout) were available. PWB layout recommendation would also be very helpful for a device such as this that has low noise requirements (although that would not be part of the Road Test). The platform allowed extensive testing capabilities of the MAX30001 device. It appeared that the sensitivity and noise parameters of the board were very good, especially for a wearable market (and probably would perform on par with many high end medical instruments).
A special thank you to the Element14 Road Test Program that allows individuals to test selected development platforms. The results provided by Road Testers are usually fantastic helpers for anyone interested in one of these platforms.
This review is for the MAX30001EVSYS Evaluation System. The featured device on the board is a the MAX30001 which is a complete, biopotential and bioimpedance (BioZ), analog front-end (AFE). The Evaluation Board also has a MAX32630FTHR daughter card which is a rapid development platform designed to help engineers implement solutions with the MAX32630 ARM Cortex-M4F microcontroller. This daughter card comes pre-loaded with software to interface between a host PC and the MAX30001. A Windows based GUI is provided to allow quick setup and evaluation of the many features of the MAX30001.
The Evaluation System package comes with the following:
- MAX30001EVSYS Evaluation Board
- ECG Cables
- Micro-USB Cable
- Thank You card with a web address for information/software download
The evaluation of this product requires wet electrodes for adhesion of the test cables to the skin. This is a very low cost item, that would have been nice to have included, and would give a user quick access to the functions of the Evaluation System (many engineers possibly evaluating this product may not have these handy). They are available from Amazon (3M Red Dot Electrodes are the ones recommended in the Maxim Tutorial Video although most any will work as the snap size on the electrodes are very common).
Time to get started (The Fun Stuff)…
Step 1) Download the software from the Maxim website (the card shipped with my unit had the wrong address for the software but a simple search located it on the Maxim website).
Step 2) Load the software onto a PC. The first PC used was a Lenova Laptop with Windows 8.1. The installation worked with the exception of the driver. Several attempts were made playing with the installation (including the Gordon Margulieux method on his road test – Thanks Gordon). The application would run but not connect to the board. The error message on driver installation is shown n Figure 1.
Figure 1. Win8.1 Unable to Install Driver
Next attempt was on a Dell desktop with Windows XP. Installation program indicated it was installing Microsoft .NET Framework 4.0 (which appeared to work – no error messages). Driver installation failed. After connecting the board and forcing a driver install (from the driver directory created under the Maxim software installation directory) the board was properly recognized (See Figure 2). It is worthwhile to note that the power for the Evaluation Board is applied through the micro-USB connector so no additional power source is required.
Figure 2. Successful Driver Installation
Once the driver was installed starting the application was attempted but failed with an exception. The solution was to go to Microsoft’s website and download/install the .NET Framework V4.0. Once this was complete the Evaluation System software properly started.
Before jumping into testing a Setup Test was also run on a Dell Desktop with Windows 7. The software appeared to install correctly (including the .NET Framework portion – as with XP). Driver installed correctly with no extra steps or issues (plugging in the board following installation was seamless and the board was immediately recognized). The application failed to execute (exception). Microsoft .NET Framework V4.0 was then installed and the application started correctly. This was the same issue as for XP. It appears the MAX30001EVSYS Setup Software does not properly install the .NET Framework. As a side note, the Windows 8.1 platform already had the .NET Framework on it and the setup program (correctly) did not try to install it.
Step 3) BioZ Measurement: Connect the ECG cables to the wet electrodes and attach them to a human (me). It is a good idea to watch the video listed on the Maxim website under the MAX30001EVSYS page. Figure 3 provides a snapshot of this video.
Figure 3. BioZ Video Tutorial
The video provides guide for BioZ settings and measurement including where to attach the wet electrodes. For reference, for the BioZ feature, the Black lead (right lower torso) is in the BB input on the Evaluation Board, the Red lead (left lower torso) is in the BIP input on the Evaluation Board, and the White lead (upper right chest) is in the BIN input on the Evaluation Board.
The MAX30001 Evaluation software Home Tab is shown in Figure 4. You may notice the Quick Start Settings provided on the GUI software Home tab for the “BioZ Only” setup differs slightly from the recommendations on the tutorial video. Both configurations will give you reasonable plots (as long as you set the BioZ Milliohm Scale setting in the Options menu.
Figure 4. Evaluation Software GUI Home Tab
The plot in Figure 5 shows the results of the BioZ measurement using the settings recommended in the tutorial video.
Figure 5. BioZ Measurement with Tutorial Settings
The plot in Figure 6 shows the results of the “BioZ Only” Quick Start settings. Changing the current generator magnitude from 8uA to 32uA caused a shift in the neutral point of the plot but appears to not have had a large affect on the measurement. Changing the frequency of the current generator has some notable effect on the output as well. The easiest change to notice is when you change the filters on the BioZ Channel setup tab.
The GUI software makes it extremely easy to modify settings for evaluation (plug for Maxim Software guys). Playing with these settings it is possible to get reasonable results even with shallow breathing (yes, I have to give a plug to the chip designers as well).
The GUI software allows you to capture the data and save it to a CSV text file that can be used by Matlab or Excel to plot and evaluate the captured data. This is a great feature. Another great feature of the software is the capability to read and write the MAX30001 device registers. This feature allows the Evaluation System to be used to optimize the operational settings and immediately know the associated register settings.
One thing I would have liked to see in the software was a Zoom function on the Plot tab (even if it only worked when not capturing). This would have allowed finer and quicker evaluation of the waveforms without having to export to another program.
Step 4) ECG Measurement: ECG was of more interest to me (having an irregular heart beat). The “Run All” quick start setting on the GUI software Home tab works for both the BioZ feature and the ECG feature. The input leads just need to be moved on the Evaluation board. Moving the Red lead to ECGP and the White lead to ECGN sets up for ECG monitoring (no changes to the “Run All” configuration). The wet electrode positions on the body were not changed. The plot in Figure 7 shows for the results of the ECG capture.
Figure 7. ECG Measurement with Quick Start (Run All) Settings
Note that the red circles added to the graph by the R to R function (for measuring heart rate) work well on a normal Sinus Rhythm. Beats can be are missed when the heart does a short interval beat (near 3 and 7 seconds on the plot). The Beat to Beat Heart Rate measurement did change down to the 30s when this occurred indicating the beat really was missed. There are settings on the ECG Channel tab of the GUI software that allow you to tweek the sensitivity and windowing functions of the R to R function (modifying the settings provides significant improvement in the R to R function for irregular heart rhythms).
As an experiment on lead placement I moved the black lead to my upper left chest position. The ECG was run and the plot shown in Figure 8 shows a nearly identical waveform. This electrode configuration on the body is typical of where the medical industry places the electrodes for a three lead measurement (See Figure 9). The labels on the ECG cables (see Figure 10) match this configuration also with RA (white) close to the Right Arm, the LA (black) close to the Left Arm and the LL (red) on the lower left of the torso (LL normally stands for Left Leg).
Figure 9. Typical ECG Electrode Placement (Illustration courtesy of Mindray)
Figure 10. Evaluation System Electrode Labels
These connections make sense as the black lead is really just a reference and the red and white leads are measuring the typical view for cardiac monitoring (Lead II – position is inferior view of the apex of the heart). Lead I and Lead III measurements can easily be taken by changing the locations of the wet electrodes to span the area of the chest providing the ‘view’ of the heart across alternate planes. I have added a section to the end of the report to provide references that addresses typical industry standard ECG attachment locations.
Step 4) PACE Measurement: The Pace channel features were not tested as I don’t know anyone with a Pacemaker. The features of the device for people with Pacemakers looks very interesting and seems to be a great addition to the device.
Additional Comments: Documentation was lacking in my opinion. All of the features and functions are not described in any users guide (etc.) so much time can be spent playing with knobs and settings and figuring out how it works. The Evaluation System does a great job of letting you do that (besides who reads instructions?). In reality, it would be useful to have documentation and schematics (and PWB layout recommendations). This is particularly true on a board that has so many jumpers along with several potentiometers.
Some useful information regarding ECGs and electrode placement:
The MAX30001 Evaluation System matches the AAMI/AHA (American standard) color-coding standards (Association for the Advancement of Medical Instrumentation).