The Low-Energy Blood Strain Meter design makes use of a microcontroller with Low Energy expertise, appropriate for battery-operated medical gadgets.
A blood strain meter, referred to as a sphygmomanometer, is a necessary medical device for monitoring blood strain. It usually consists of an inflatable cuff to constrict blood movement and a pump for inflating the cuff. Trendy digital variations of those meters make use of the oscillometric methodology for measuring blood strain, which makes use of a piezoelectric strain sensor to gauge each systolic and diastolic pressures precisely. The Low-Energy Blood Strain Meter reference design was developed by Microchip utilizing the PIC24FJ128GC010 system-on-a-chip (MCU). This microcontroller unit is supplied with eXtreme Low Energy (XLP) expertise, optimizing it for vitality effectivity. Notably, it consumes solely 18 nA in Deep Sleep mode and 240 nA when working the Watchdog Timer (WDT) in the identical mode. Its Run mode energy consumption is 180 µA/MHz, making it a pleasant alternative for battery-operated medical gadgets.
The technical capabilities of the MCU are spectacular, encompassing a variety of options to assist complicated medical functions. It features a 16-bit delta-sigma Analog-to-Digital Converter (ADC) with two differential channels, a 12-bit pipeline ADC able to 10 Msps throughout 50 channels, and two 10-bit Digital-to-Analog Converters (DACs) that function at 1 Msps. Moreover, the MCU is supplied with two operational amplifiers, three comparators, three voltage references, a Cost Time Measurement Unit (CTMU), and USB assist for machine, host, and OTG configurations with lively clock tuning that eliminates the necessity for a crystal. A segmented LCD driver with a cost pump enhances the machine’s show capabilities, rounding out its complete characteristic set.
The machine’s main energy supply is both 4 1.5V AAA alkaline batteries or the USB’s VBus line. The MCP1802 Low Dropout (LDO) regulator then steps down the 5V or 6V important enter voltage to a 3.3V VDD output. The firmware features a 2-pass shifting common filter with a cutoff frequency of three.5 Hz, which processes the uncooked ADC samples collected from every ADC channel.
The design can measure each blood strain and pulse price whereas the cuff is inflating. This Measurement Whereas Inflating (MWI) approach shortens the general measurement period and minimizes the discomfort related to extended cuff strain.
In operation, the meter’s motor initially quickly inflates the cuff to 30 mmHg. Following this, the motor shifts to a sluggish mode, progressively and linearly inflating the cuff. Because the cuff strain will increase to a stage that begins to limit blood movement, the arterial pulse turns into detectable by the strain sensor, permitting for correct readings.
Microchip has examined this reference design. It comes with a invoice of supplies (BOM), schematics, meeting drawing, printed circuit board (PCB) format, and extra. The corporate’s web site has extra information in regards to the reference design. To learn extra about this reference design, click on right here.
