JPS6099231A - Pressure converter of electronic hemomanometer and zero point adjustment thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

This article is about the structure of the pressure sensor of electronic blood pressure B1 and its zero point adjustment method.The semiconductor pressure sensor is one of the pressure sensors of the electronic blood pressure monitor.This semiconductor pressure sensor is 13 High sensitivity + 21 Q No mechanical moving parts, strong against impact + 31 It is often used because of its small size; however, it has disadvantages (41 High offset voltage 15 + Large temperature coefficient of offset voltage). Because of these shortcomings, it is generally necessary to perform zero point adjustment.Even if the zero point is adjusted at room temperature, the temperature coefficient of the offset voltage is large.For this reason, it has been conventionally necessary to adjust the output of the AD converter when turning on the capacitor. In addition to subtracting from the output when pressurizing and using the difference as the pressure value, we perform zero point correction on the lift, and also take measures to ensure that the AD converter operates normally even when there is temperature drift.Specifically, (The polarity of the zero point may differ due to temperature drift.) Many AD converters do not work with input terminals with different connections.Therefore, the following method was used. Use an AD converter. (21 Use a unipolar AD converter to shift the voltage in the direction of the pressure signal voltage when adjusting the zero point. 13) Use a monopolar AD converter to set the zero point adjustment to zero. fkli, which is close to the potential, is adjusted to the surrounding area, and the subsequent circuit adds the potential to the signal potential and applies it to the A and D converters.The bipolar AD converter has a complex configuration and a large number of parts.Electronic blood pressure converter The pressure transducer must be low cost and at the same time not only have a small number of parts but also be easy to adjust. The burden was heavy and he was prone to making mistakes.

Although the method of [31] was easy to adjust, it required some additional circuitry. The present invention eliminates the above-mentioned drawbacks by using a commonly used double-integrating AD converter and applying a potential to the non-inverting terminal of the integrator. This will be explained below according to the attached drawings. FIG. 1 is a diagram showing a pressure detector of an electronic blood pressure monitor. The signal voltage of the semiconductor pressure sensor l is differentially amplified. Since the offset voltages of the pressure center 1 and the operational amplifier are also increased, the zero point correction circuit 2 is required. When the voltage is 0mm and 11g, set the voltage at the adjustment terminal P to be ay, and apply AD to the pressure
The output of the converter 4 is ii1/Ju by the gain adjustment circuit 3 so as to indicate the pressure at that time. The pressure value is reverse processed by the CPU 5. When the AD converter 4 is unipolar (positive polarity input in the figure),
If the voltage at the adjustment terminal P becomes negative due to drift, it will no longer operate. In order to avoid this, after the sensitivity adjustment, the voltage at the adjustment terminal P must be slightly shifted by the zero point correction circuit 2 again. It may seem like it would be a good idea to shift the voltage at the zero point adjustment stage from the beginning, but
If the zero point is not completely adjusted, the zero point will also shift during gain adjustment, and even if the pressure is returned to Om m-Hg, the display will not show Om m, Hg. This zero point adjustment method corresponds to Conventional Example 121. FIG. 2 is an example of a conventional pressure detector. electronic switch 6
, Performance, Amplifier 7. Comparator 8. An integral capacitor C1 and a logic circuit (not shown) constitute a sub-integral type AD converter. A double-integration type AD converter charges a capacitor with a signal voltage for a certain period of time, and measures the time until the capacitor is completely discharged with a constant current. First, without applying any pressure, the zero point correction circuit 2 adjusts the 'i' of the adjustment terminal P.
t fE k Adjust to DV. In this state, since the offset correction voltage No is superimposed on the signal voltage by the adder 9, the pressure Ib has some value. Next, pressure is applied, and the gain adjustment circuit 3 adjusts it so that the difference with the output of the AD converter at that time shows a constant pressure of 'J'Jr.The adjustment is only at and h and does not require any additional work. , an operational amplifier is required as an adder. FIG. 3 shows an embodiment of the present invention, and FIG. 4 shows waveforms of various parts for explanation and clarity. (A) is the output waveform of the operational amplifier 7, fBl is the output waveform of the comparator 8, and I
O+ indicates the input waveform of the electronic switch 6. When no pressure is applied, the potential of the adjustment terminal P is adjusted to OV (or its vicinity) by the zero point correction circuit 2. The adjustment method is the same as the conventional example shown in Fig. 2, in which the AD converter output at this time is subtracted from the output when pressurizing, and the gain adjustment circuit 3 adjusts the difference so that it becomes the pressure value. In terms of the circuit, there is no adder, and a voltage B obtained by dividing the reference voltage BR by resistance is applied to the non-inverting terminal of the liquid amplifier 7 constituting the integrator. Therefore, even if the polarity of the signal voltage E8 changes due to OV or drift, it operates as AD conversion. Electronic switch 6 is driven by an external pulse. If the charging time by the signal voltage E8 is Tl, and the discharging time of the integral capacitor is T2, then the charge is conserved at 7t, I C,T ], = d@T 2 [,1 holds true. Here, XC represents a charging current, and ld represents a discharging current. It is obtained by dividing the reference voltage FiFl of the non-inverting amplification terminal of the amplifier 111□i unit 7, and even if the No. 48 voltage E8 is ○■, a potential difference occurs across the resistor R1. Therefore, the AD converter is operating. Therefore, charging knowledge 4th grade engineering C
, discharge ■, and discharge d are given by the following equations. lc = (Ep −1−El)%] 121Ep:
The voltage value of the adjustment terminal P is d = (ER-El)/R2131. Therefore, T2 can be determined from 111 using the following formula. El is obtained by dividing the reference voltage KR by resistance. J = (Rs/ (Rs + Ra))・EiR Substituting K into this formula and rearranging it, from the formula 151, we get that the reference voltage RR in the state of K p = OV.
Regardless, the output value T2 remains constant. That is, even if the reference voltage BCR changes, the output of the ADD converter at a pressure of Orr+, rnH(l does not change.Furthermore, if -ip is proportional to the reference voltage ER, then the output of the AD converter will change to the reference voltage. It is extremely stable against fluctuations in KR (largely due to factors such as temperature changes and electrophoresis voltage fluctuations).The present invention provides a two-way integral type AD converter with a simple groove bottom and easy adjustment. A pressure detector for all types of blood pressure readings has been created.The cost reduction due to the reduction in adjustment costs and the number of hardware parts is extremely effective for mass production. Furthermore, as mentioned above, the characteristic of being resistant to fluctuations in the reference voltage is essential in producing a highly accurate pressure detector, and this alone can be said to be a great effect of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a pressure detector of an electronic blood pressure monitor, FIG. 2 is a conventional example, FIG. 3 is a diagram showing an embodiment of the present invention, and FIG. 4 is a diagram for explaining the same. J...Semiconductor pressure sensor 2...Zero point correction circuit 3...Gain adjustment circuit 4...AD converter 5...CPU 6...Electronic switch 7...A-amplifier 8...・Comparator 9...Contributor P...Line 1 adjustment terminal ER...Reference voltage E8...Signal voltage EOO・Offset correction voltage C-φ・Integrator capacitor +2 +3 +4...Resistance or more Applicant Seiko? −Representative of Denshi Kogyo Co., Ltd. Patent Attorney Mogami

Claims (1)

[Claims] An integrator consisting of a 111Ji capacitor and a differential amplifier, a comparator for determining the output of the integrator, and a predetermined 1 Hi 1 by inverting the output of the ratio axis device. A logic circuit that generates a 1-width pulse and a signal from the logic circuit turn off the charging/discharging current to the integrator! a base voltage having a polarity opposite to that of the signal voltage, and one or more resistors, the charge current is determined by the signal voltage and the resistor, and the discharge current is determined by the reference voltage and the resistor, respectively. The electronic blood pressure IT pressure converter is characterized in that the reference voltage is resistively divided and applied to a non-inverting terminal of the operational amplifier to operate as a double integration type AD converter. (2) A zero point adjustment method for an electronic blood pressure pressure converter, characterized in that the signal voltage related to the pressure applied to the electronic switch is kept within a voltage range covering predetermined positive and negative polarities when no pressure is applied.