Yes, the AECG100 can control the time difference between PPG and ECG signal, this function can help DUT to verify the PWTT accuracy.
No, it is currently in the same operating software, but the operating software will detect the difference of the module, automatically set the different operation screens.
Shading, light blocking, need DUT to deal with the mechanism.
The AECG100 has more function as follows:
(1) Supports SpO2
(2) More waveform parameters setup
(3) More PD Sample Rate
(4) Software control LED maximum light intensity (shipping SW only)
(5) SW control trigger level
Can simulate skin color by controlling the DC value of PPG simulator, but the real connection between skin color and DC value needs to be defined by the user.
A. Please refer the answer to the question 1. First, roughly determine the positions of both PD/LEDs. DUT must be able to see the simulator output waveform and the both parties need to see each other. AECG100 reflective series, the R and IR positions are as shown in the photo below:
(For reference only)
B. How to determine that AECG100 has detected the optical signal of the DUT?
1) In the following screen of the AECG100 software, click on the “Sampling” (vertical writing) in the screen lowest left corner (do not start the simulator “Play” function at this time):
2) Click “Signal”, check “Switch-RED” and “Switch – Infrared” , as below photo:
3) Click “Sampling” (horizontal writing), start the sample function.
4) Select the -/+ amplify range to properly display the detective intensity, as below photo:
5) May click “Freeze” function to freeze the captured waveform, as below photo:
6) Using TI AFE4403 EVM as DUT, can see the waveforms as follow figure:
Two lights should be interlaced startup (Low Active), if there is only high or only low Condition, the “Trigger Level” should be adjusted.
7) Trigger Level adjust explanation:
Dynamically adjust R/IR Trigger Level value without Freeze and proper magnification, the order is, first fix the IR at the maximum value of 255, because the IR switch will affect R switch. In this case, the switching mode of the IR should be at a high level, if it is at a low level, indicates that the simulator has a problem or the light of the DUT is too strong (need to adjust the hardware parameters of the simulator), if the IR is stable at the high level, you can further adjust the value of R, slowly adjust from high to low until you see the appropriate stable low level pulse, and then adjust the IR Trigger Level slowly decreases until you see a stable, interlaced low pulse. At this point, it means that AECG100 can see the sequence of the DUT light turn on stably, if cannot get the correct adjustment, the AECG100 need to troubleshoot or adjust the inside hardware parameters of AECG100.
C. Confirm DUT received the light of AECG100
This part needs to be judged from the information received by the DUT. We recommend setting the two lights to different types of waves first. After adjusting the Trigger Level, stop Sampling and return to the following screen.
Select R or IR, as follows:
Select waveform type, as follows:
And then click ”Play” to play the waveform, as follows:
DUT is TI AFE 4403 EVM, the detected waveforms as follows:
There are 4 different waveforms, from top (C1) to bottom (C4):
C1: LED 1, IR LED turn on waveform (the sample data from IR LED turn on).
C2: LED 1 Ambient, IR LED turn off waveform, in general case, this is noise only low amplitude waveform, if it is not noise waveform, means the Trigger Level is not correct or DUT sampling way is unacceptable.
C3: LED 2/LED 3, R LED turn on waveform (the sample data from R LED turn on).
C4: LED 2/LED 3 Ambient, R LED turn off waveform.
The recursive formula as follows, the user must define the 110.0 and 25.0 parameters to get the DUT SpO2. Normally, to get the recursive line after clinical, and then determine these two values.
Then, to change the SpO2 value, user can modify the PI(R) or PI(IR) value.
When modifying the SpO2 value, the checked (blue dot) PI(R) or PI(IR) will be modified automatically, as follows, when the SpO2 value change to 95%, the PI(R) change to 2.399.
As above, the “Lock DC” is unchecked, so the DC value will be modified when PI(R) modified, but the AC value will still the same.
User can modify all the values which can be changed, and the PI(R), PI(IR), SpO2 value will be changed automatically.
The value that can be entered in the above figure is the compensation for the customer to make the offset according to the condition of the system test fixture (this value may come from the circuit dark current / AFE offset error / external ambient light increase the DC level, etc.).
Possibility: Line/main frequency interference (e.g. 60Hz in Taiwan)
We could use the AECG100 and TI AFE4403 EVM to do some tests.
Test 1: 60Hz Notch Filter ON/OFF (AECG100 DC 625mV and AC 30mV)
Blue Line: Disable AFE4403 60Hz Notch Filter
Red Line: Enable AFE4403 60Hz Notch Filter
Test 2: Mobile Power Pack / USB Isolator
Blue Line: AECG100 PC software Mode, DC 3000mV, AC 30mV
Red Line: AECG100 standalone mode waveform output with power supply of mobile battery pack
Green Line: TI AFE4403 connects to USB Isolator
Result:
1. It indicates that the interference mainly comes from the receiving end (TI AFE4403).
2. It's confirmed that USB Isolator could decrease the interference.
Please refer to above figure. The definition of response time is that the delay time between A (PD reception) and B (LED emitting). However, the optical signals between A and B are difficult to measure. Therefore, WhaleTeq uses oscilloscope to measure the electrical signals between A” and B” as the response time.
We'd expect your attention that the response time would be varied due to incident light intensity, emitted light intensity and trigger level. Please refer to the below figure.
A. Incident light intensity would influence the delay time. Thus T2 > T1. Moreover, please notice that the incident light intensity would be affected by emitting intensity of DUT LED, relevant position (the distance and the angle between DUT PPG sensor and AECG100 diffusion film) and wavelength.
B. Different trigger level leads to different response time. Please refer to the figure and you can tell T1/T2 would be increased if the trigger level is increased.
C. There are 2 trigger levels for the AECG100 and the relationship of these 2 trigger levels is –
Trigger Level (OFF)=Trigger Level (ON) + OFFSET
The OFFSET is generated by electrical circuit.
*Trigger Level/OFFSET…are relative values and we haven't calibrated those values as absolute values.
D. It's possible that some DUT would have a longer LED off time and this is because of the large capacitance design of DUT.
E. In accordance with our experience, most T1/T2 values are smaller than 1us while T3/T4 values vary from each DUT. Please notice that it's possible to get an inappropriate test result when DUT is sampling after LED turns off per previously described as A’ in question 7. Also, user could get another inappropriate test result when T3/T4 values are larger per described in D (large capacitance design of DUT).
Conclusion:
As there are too many variables, WhaleTeq's test environment shall be different from customer's test environment.
Therefore, the response time we advised is only for reference. We strongly suggest customer to test DUT with the AECG100 to confirm the actual response time.