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Figure 12 Desired Device selection from the list   

 

When  the  desired  device  is  selected  from  the  list,  the  app  will  form  a  connection  to  the  device  over  Bluetooth  low  energy.  
After connection the device control will open fully and control over the device can begin.  

3.4 Measured Results 

The device pictured below is the foot BCM device.  The On/Off button is on the underside of the device covered by the device 
serial number. A short press of the On/Off button will turn the device on.  A longer press of about a second is required to turn 
the  device off.  The  On/Off  status of the  device can be verified  by looking at the top of the device in the LCD window.  The 
backlight will flash periodically while the device is powered ON.

 

 

Figure 13 Measurement setup   

 

The first step is the Calibration - press the “Calibrate” button.  As in the figure below the button will change to “Scale Ready” 
when the calibration is complete. Even though the front panel of the GUI shows up the weight, height and age options it’s not 
necessary entering those values as the device is able to measure the weight. 

Summary of Contents for tidu131

Page 1: ...nalog circuit design of weight scale and body composition measurement applications Two separate signal chains are discussed in this document one for weight scale WS measurements and the other for body composition measurement BCM analysis Design Resources Design Archive ZIP File All design files AFE4300 Product Folder 1 Design Summary This design takes a block level approach for designing a Weight ...

Page 2: ...erential voltage across the middle nodes The challenge in designing a weigh scale is how to make accurate measurements of the signal produced by the resistor bridge because this signal is usually very small mV magnitude Body composition is traditionally obtained by measuring the impedance across several points on the body and matching the result in a table linking both the impedance measured and t...

Page 3: ...rodes and the current that flows through the tissue 2 2 Hardware overview and circuit description 2 2 1 Weight Scale Analog Front End Figure 4 Weight Scale Front End 2 2 1 1 Overview and Gain Calculation The weight scale front end has two stages of gain with an offset correction DAC in the second gain stage The reason for using INA and PGA is to fit different input voltage from the sensor bridge T...

Page 4: ...ut signal at the input of the first gain stage CM Common mode Range 2 2 1 3 Input Differential Dynamic Range The max differential INP INN signal depends on the analog supply reference used in the system This range is shown in the equation below The gain in equation above is the product of the gains of the INA and the second stage gain The full scale input from the bridge signal typically consists ...

Page 5: ...sed to obtain the final result 2 2 2 1 AC rectification Figure 5 BCM in AC Rectifier Mode The top portion of Figure 5 represents the current injection circuit A direct digital synthesizer DDS generates a sinusoidal digital pattern with a frequency obtained by dividing a 1 MHz clock with a 10 bit counter The digital pattern drives a 6 bit 1 MSPS DAC The output of the DAC is filtered by a 150 kHz se...

Page 6: ...t digitizer used in the weight scale chain Ultimately the dc output is proportional to the module of the impedance The proportionality factor can be obtained through calibration with the four external impedances Although with one single frequency or measurement only the module of the impedance can be obtained two different frequencies could be used to obtain both the real and the imaginary parts 2...

Page 7: ...B Serial Dongle along with the Foot BCM data acquisition system The pictured device connects to the app via Bluetooth low energy Figure 7 Health Hub Measurement Setup Hardware Description 3 2 Health Hub App 3 2 1 Interface Overview Health Hub is designed to allow the control and display of many BLE enabled health monitoring devices on a single screen The screen is divided into multiple discrete ar...

Page 8: ...to have the PC finding the device To this end the desired device must be in advertising mode Generally the devices will advertise any time they are turned on and not connected When the Foot BCM is in advertising mode the display will be flashing To find a device press the Discover Devices button as shown in the figure below The icon will change to discovering and will find devices for about ten se...

Page 9: ...Devices the device controls appear as in the figure below Figure 10 BLE enabled device not found After a device has been found the device control will appear as in the figure below Figure 11 Device found connection can be established When the Connect button is pressed a selector will be shown as below ...

Page 10: ...of the On Off button will turn the device on A longer press of about a second is required to turn the device off The On Off status of the device can be verified by looking at the top of the device in the LCD window The backlight will flash periodically while the device is powered ON Figure 13 Measurement setup The first step is the Calibration press the Calibrate button As in the figure below the ...

Page 11: ...ates that the foot BCM device is ready to measure the user s weight Ask the subject to step on the scale and remain still Press the measure button Figure 15 Foot BCM Measuring The following figure shows up some measurement results Figure 16 Measurement results ...

Page 12: ...esponsible for compliance with all legal regulatory and safety related requirements concerning its products and any use of TI components in its applications notwithstanding any applications related information or support that may be provided by TI Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failur...

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