BP01-type pressure sensor application portable blood pressure monitor

1 Overview BP01-type pressure sensor for monitoring blood pressure, specially designed for portable electronic sphygmomanometer. It uses the precision of thick-film ceramic chip and nylon plastic packaging with high linearity and low noise and stress of the outside world; using an internal calibration characteristics and temperature compensation mode, which improves measurement accuracy, stability and repeatability, at full range, accuracy of ± 1%, zero offset is not greater than ± 300 μ V. The main performance parameters 2BP01 BP01 internal equivalent circuit and outline package as shown in Figure 1, table 1 lists the power supply voltage Vs BP01 as 5.0V, ambient temperature TA as 25¡æ, main performance parameters. BP01 limit parameters are as follows: • maximum working voltage: 20VDC; • Max pressure: 1500mmHg; • operating temperature range: 0 ~ 70 ° c; • pin welding temperature (max): 250 ° c (2-4 seconds). 3 the electronic sphygmomanometer based BP01 3.1 works with a portable electronic BP01 sphygmomanometer principle electric circuit as shown in Figure 2, which consists of bias power circuit (A1, A2), lead processing circuit (A3-A6), show circuit (A7) and pressure sensor (BP01), the blood of their blood pressure measured in the range 0-200mmHg 0.1mmHg, resolution into a working power supply 9V laminated battery. Now the main circuit in the sphygmomanometer works as follows: a. bias power circuit power circuit with built-in reference voltage dual op amp LM10 composition, pose with phase amplifier A1, A2, which constitute the follower is the built-in reference voltage is enlarged for use as a pressure sensor BP01 Vs the bias voltage, its value from the next Vs-decision: Vs = Vref (1 + R2/R3) type: Vref for the LM10 built-in reference voltage. Its value is 200mV, set this value, together with circuits of R2 and R3 value substitution can seek on-bias voltage 5V Vs value. B £ ® pre processing circuit lead processing circuit by A3-A6 four operational amplifier, A3 constitutes dysfunctional bias circuit to circuit compensates unbalance; A5 form the emitter, used for pressure sensor output signal BP01 isolation buffer; A4, A6, which constitute the amplifier gain AV from next-decision: AV = 1 + (R1/RT) to ignore disorders, lead processing circuit output voltage Vout: Vout = 2 (1 + R1/RT) VIN type: VIN for pressure sensor BP01 's output voltage. C £ ® display circuit display circuit selection of three and a half's drive. Working pressure sensor output via front BP01 processing circuit amplification by the display driver to drive the LCD to read out the measurement of blood pressure values. 3.2 debugging method for a zero-voltage output adjustment. at zero pressure output adjustment disorders potentiometer, sphygmomanometer RP1 shows value of 000.0, you can view completed zero pressure output adjustment. B £ ® front circuit gain adjustment pressure sensor of the full output and BP01 bias voltage is 5V, when, in bias-200mmHg pressure output to 10mV, its corresponding display driver input to 200mV, front circuit gain AV-200mV/10mV, in this way, use the formula front Av to reverse launch gain resistors RT value. If selecting resistors R1 is 10 k Ω, you gain resistors RT should be 1.1 k Ω. Debugging can be adjusted by potentiometer output values, and then use multimeter measured the potentiometer resistance, then replaced by a fixed resistance. C £ ® full adjustment of the full adjustment, first in the show circuit input plus 200mV voltage, and then adjust the potentiometer RP2, so that it reads 199.9mmHg. Adjustment is complete, the General should be repeated several times, so that the display value to reliably meet the precision requirements. 3.3 components selection to ensure measurement accuracy, the circuit's selection of the external components is also an important aspect to be ignored. In General, the potentiometer RP1, RP2 should use 1% precision metal film resistors multi-turn potentiometers; should use 1% precision metal film resistors, capacitors General selection of polyester film or MICA capacitors. 4 closing BP01 using pressure sensors and other devices for portable electronic sphygmomanometer, it should be noted: for different bias voltage and the output is different, thus lead processing circuit gain should be adjusted to meet the full range of different requirements.