The Household portable Finger clip oximeter is highly flexible ,can quickly measure the percentage of human blood oxygen saturation (SpO2 ) and pulse rate on the basis of non-injury.Has won wide and high praise and has sold well continuously.
As the Hemoglobin in blood has different absorb ability of red light and infrared light.Compare the Hemoglobin with oxygen (HBO2) and the Deoxygenated hemoglobin(HB) ,HB absorbs more red light and less infrared light, HBO2, on the other hand, absorbs less red light and more infrared. The Red and infrared leds are next to each other in Structurally,thus can allow light pass through in the finger pointed single position conveniently.Light travels from one side of the finger to the other side, after picked up by a photodiode and produce a proportional voltage to it.
Runic as a High- tech company with high performance analog signal chain design capabilities, our product line such as OP Amps, Comparator, Analog Switch, LDO,etc. Can match very well with the design of consumer medical products such as Finger clip oximeter.
The typical schematic block diagram of portable Finger clip oximeter is as below:
In the picture above,the Analog switch RS2105 of Runic is used to switch red LED and infrared LED lamps,they are time-sharing and modulate at a certain frequency. The OP Amp RS321 works with the DAC inside in the MCU to produce a constant current output signal, because the constant-current operation of LED lamp can obtain a relatively stable wavelength, the emission current usually reaches tens of mA, so the on-resistance of analog switch should be less than 1Ω, and the on-resistance of our RS2105 is 0.6Ω, which meets the application requirement well.
On the side of the photosensitive receiver, the OP Amp RS622 is used for the photoelectric conversion, which requires the input bias current Ib of the OP Amp to be pA-level, and the bandwidth of the OP Amp needs to be more than 5 MHZ to satisfy the fast response.The low noise series OP Amp can better to improve the resolution of the system. In the power topology, one is to use two cell dry batteries(3V) boost to 5V and then buck to the system circuit to use, the other is use lithium battery,which can be cycle charged for use.Our low power consumption LDO RS3236 are suitable for both topologies.
The main parameters of Runic’s low noise OP Amp RS622 are as below:
◆ Wide voltage supply range: 2.5V~5.5V;
◆ Low offset voltage: 0.7mV typical, 3mVmax;
◆ Low temp shift: 2uV/°C typical;
◆ Low input bias current IB:1pA;
◆ Gain Bandwidth: 7MHz;
◆ Quiescent current: 600uA per channel;
◆ Noise factor:11nV/√Hz.
The main parameters of Runic’s Analog switch RS2105 are as below:
◆ Wide voltage supply range: 1.8V~5.5V;
◆ Low on-resistance: 0.6Ω, 1Ω max;
◆ Output current continues:500mA;
◆ -3dB Bandwidth：30MHz;
◆ Quiescent current: less than 1uA;
◆ Has MSOP-10，TDFN-3*3-10L package for your choice.
The main parameters of Runic’s low consumption LDO RS3236 are as below:
◆ Wide input voltage range: 1.7V~7.5V, support 4 cells dry battery input application;
◆ Internal max output current limit: >500mA;
◆ Ultra-low quiescent current: 20uA;
◆ Ultra-low drop voltage :1mV/mA;
◆ Ultra-high PSRR: 70dB/Hz;
◆ Output voltage density optional: 1% or 2.5%;
◆ Kinds of fixed -output voltage and many packages such as SOT-23, SOT-89-3, SOT-23-5, UTDFN-1*1-4L for your choice.