JP5247406B2 - Resistance value output circuit and ear-type body temperature measuring device using the same - Google Patents

Description

  The present invention relates to a resistance value output circuit and an ear-type body temperature measuring device using the resistance value output circuit.

  For example, in an operating room or an intensive care unit, it is indispensable to measure the body temperature of a patient during treatment, and there is a need for a highly reliable body temperature measuring apparatus that can continuously measure body temperature over a long period of time. Furthermore, in order to continuously measure the patient's temperature, it is also necessary that the burden on the patient is small. As a body temperature measuring device that meets such a need, an ear-type body temperature measuring device that measures the temperature of the eardrum by inserting a temperature measuring unit into a patient's ear canal has attracted attention.

However, in the case of the conventional ear-type body temperature measuring device, there is a problem that the measuring device main body becomes large, and the miniaturization thereof has been demanded. In response to this, a probe including a temperature measuring unit as described in JP-A-2006-250883 (Patent Document 1) and JP-A-2007-111363 (Patent Document 2) is downsized and measured. An ear-type body temperature measuring device in which the device main body is also miniaturized is known.
JP 2006-250883 A JP 2007-111363 A

  It is an object of the present invention to provide a resistance value output circuit that can be mounted on an ear-type body temperature measuring device to reduce the size of the ear-type body temperature measuring device, suppress an increase in cost, and maintain high temperature accuracy.

  It is another object of the present invention to provide an ear-type body temperature measuring device that can obtain a thermistor temperature resistance value output with high accuracy while miniaturizing and suppressing an increase in cost.

The present invention includes N analog switches that are turned on / off by a 1 (HIGH) / 0 (LOW) signal of each digit of an inputted N-digit (N is an arbitrary natural number) binary signal, N resistors connected in parallel to each of the analog switches and connected in series with each other, each having an individual resistance value, and measured resistance values of the N individual resistors are stored. An actual resistance value storage unit, an analog resistance value output terminal commonly connected to the N analog switches and resistors, a temperature command input unit for inputting an output temperature command, and a temperature value and a thermistor thermometer output The temperature / resistance value correspondence storage unit for storing the correspondence relationship with the resistance value, and the temperature value and thermistor temperature of the temperature / resistance value correspondence storage unit for the output temperature command input by the temperature command input unit Refers to the correspondence relationship between the output resistance value of, determine the output should do resistance value of the thermistor thermometer corresponding to the output temperature command, temperature resistance value calculation unit for outputting the N-digit binary code representing the resistance value And ON / OFF of the corresponding analog switch of each of the N analog switches is determined according to binary code 1 or 0 of each digit of the N-digit binary code output from the temperature resistance value calculation unit. Rather than referring to the measured resistance values of the N individual resistances stored in the actual resistance value storage unit, the thermistor thermometer corresponding to the output temperature command obtained by the temperature resistance value calculation unit should be output. An N-digit binary code corresponding to the resistance value is input, and a combination of a plurality of resistors is obtained to obtain a series combined resistance value that matches the resistance value represented by the N-digit binary code. Each of the N analog switches is turned on / off so that a combination of a plurality of resistors can be realized, and N digits 1 (HIGH) / 0 for turning on / off the N analog switches. An output resistance value calculation unit that outputs a (LOW) signal, the output resistance value calculation unit including a digital resistance value input unit that processes an N-digit binary code from the temperature resistance value calculation unit, and the digital The resistance value represented by the N digit binary code input by the resistance value input unit is referred to the actually measured resistance value of each of the N resistors stored in the actual resistance value storage unit, and represented by the N digit binary code. In order to realize an analog resistance value commensurate with the resistance value, a corrected resistance value calculation unit for obtaining an analog switch signal that combines ON / OFF of the N analog switches, and the corrected resistance And wherein said N digits of 1 (HIGH) / 0 (LOW ) resistance value output circuit and a analog switch signal output unit for outputting a signal corresponding to the analog switch signal obtained anti value calculation unit.

In the resistance value output circuit according to the invention, the actual resistance value storage unit stores measured resistance values of the N individual resistors and resistance values of the N analog switches, and calculates the output resistance value. The corrected resistance value calculation unit in the unit refers to the measured resistance values of the N individual resistors stored in the actual resistance value storage unit and the resistance values of the N analog switches, and calculates the temperature resistance value. The combination of a plurality of resistors is obtained by obtaining a combination of a plurality of resistors so that the combined resistance value corresponding to the resistance value to be output of the thermistor thermometer corresponding to the output temperature command obtained by the section is obtained. said analog switch signal that combines N analog switches each on / off determined may be shall as possible.

Further, the present invention includes a measuring device main body incorporating a battery as a power source, and a temperature measuring probe connected to the measuring device main body in a detachable state with a connector, and the temperature measuring probe is connected to the measuring device main body. A microcontroller that controls a temperature sensor of the temperature sensor, inputs a resistance value output signal corresponding to the measured temperature from the temperature sensor, converts the resistance value output signal into a temperature resistance value, and outputs the temperature resistance value from the microcontroller. In the ear-type body temperature measuring device having a built-in resistance value output circuit that reconverts and outputs the resistance value output from the meter, the resistance value output circuit has an N-digit binary signal (N is an arbitrary natural number). N analog switches that are turned on / off by a 1 (HIGH) / 0 (LOW) signal of each digit of the N digits, and the N analog switches in parallel Are connected, and a resistor each in their entirety of the connected N pieces so that the series has an individual resistance values, the actual resistance value storage unit that stores the measured resistance value of the N individual resistances , An analog resistance value output terminal commonly connected to the N analog switches and resistors, a temperature command input unit for inputting an output temperature command, and a correspondence relationship between the temperature value and the resistance value output by the thermistor thermometer Temperature / resistance value correspondence storage unit for storing the temperature value of the temperature / resistance value correspondence storage unit and the resistance value output by the thermistor thermometer for the output temperature command input by the temperature command input unit, A temperature resistance value calculation unit for obtaining a resistance value to be output from the thermistor thermometer corresponding to the output temperature command and outputting an N-digit binary code representing the resistance value; and the temperature resistance value Calculation The actual resistance value is not determined by turning on / off the analog switch corresponding to each of the N analog switches according to the binary code 1 or 0 of each digit of the N-digit binary code output by the unit. N digits corresponding to the resistance value to be output of the thermistor thermometer corresponding to the output temperature command obtained by the temperature resistance value calculation unit with reference to the measured resistance values of the N individual resistances stored in the storage unit So that a combination of a plurality of resistors can be obtained so as to obtain a series combined resistance value that matches the resistance value represented by the N-digit binary code. ON / OFF of each of the N analog switches is determined, and an N-digit 1 (HIGH) / 0 (LOW) signal for turning on / off the N analog switches is determined. An output resistance value calculation unit that outputs a signal, the output resistance value calculation unit including a digital resistance value input unit that inputs an N-digit binary code from the temperature resistance value calculation unit, and the digital resistance value input The resistance value represented by the N digit binary code input by the unit is referred to the actually measured resistance value of each of the N resistors stored in the actual resistance value storage unit, and the resistance value represented by the N digit binary code is obtained. A corrected resistance value calculation unit for obtaining an analog switch signal combining ON / OFF of the N analog switches in order to realize a corresponding analog resistance value, and the analog switch signal corresponding to the analog switch signal obtained by the corrected resistance value calculation unit The ear-type body temperature measuring device includes an analog switch signal output unit that outputs an N-digit 1 (HIGH) / 0 (LOW) signal .

In the ear body temperature measuring device according to the invention, the actual resistance value storage unit stores measured resistance values of the N individual resistances and resistance values of the N analog switches, and the output resistance value. The corrected resistance value calculation unit in the calculation unit refers to the measured resistance value of the N individual resistors stored in the actual resistance value storage unit and the resistance value of the N analog switches, and the temperature resistance value A combination of a plurality of resistors is obtained such that a combined resistance value corresponding to the resistance value to be output of the thermistor thermometer corresponding to the output temperature command obtained by the calculation unit is obtained. analog switch signals the combination of N analog switches each on / off to allow realized can look the shall.

  According to the resistance value output circuit of the present invention, by mounting this on the ear-type body temperature measuring device, it is possible to realize an ear-type body temperature measuring device that is small in size, can suppress cost increase, and can maintain high temperature accuracy.

  According to the ear-type body temperature measuring device of the present invention, it is possible to use commercially available resistance elements having various resistance values that are relatively easily available, and thermistor temperature resistance value with high accuracy while miniaturizing and suppressing an increase in cost. Can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a device configuration of an ear-type body temperature measuring device proposed in recent years, and FIG. 2 shows a circuit configuration. As shown in FIG. 1, a proposed ear body temperature measuring device 1 is inserted into a subject's ear canal, measures the temperature of the eardrum and outputs it as a resistance value, and transmits a measurement signal of this probe 2 In addition, a cable 3 for supplying power to the probe 2, a male connector 4, a measuring device body 5 for performing temperature measurement calculation processing and other controls, a cable 6 connected to the measuring device body 5, and a tip of the cable 6 The female connector 7 is formed. The female connector 7 connected to the cable 6 of the measuring device body 5 is connected to a monitor 8 that displays the measured temperature.

  As shown in FIG. 2, the main components of the measurement apparatus main body 5 are an AD converter 51 that AD converts a resistance value corresponding to the measurement temperature of the probe 2, and a differential amplifier 52 that amplifies the temperature measurement signal of the probe 2. A control signal processing circuit 53 for performing digital arithmetic processing, a resistance value output circuit 54 for reconverting the measured temperature digital signal obtained by the control signal processing circuit 53 into an analog temperature resistance value of the thermistor thermometer on the monitor 8 side, and a switch group 55 (Switches S1, S2, S3), switching line group 56 (SL1, SL2, SL3), resistor group 57 (R1, R2, R3, R4), cable 6, and female connector 7.

  The probe 2 is connected to the measurement apparatus main body 5 through the cable 3 and the male connector 4 at the time of use. The probe 2 includes a first sensor 25 for temperature measurement and a second sensor 26 for correction described later. The sensors 25 and 26 are thermistors. The resistors R3 and R4 are provided in the probe 2 in FIG. 2, but they may be provided in the measurement apparatus main body 5. The male connector 4 is preferably a conventional card edge connector. Individual information such as calibration values is recorded on this card.

  The detection signals of the first sensor 25 for temperature measurement and the second sensor 26 for correction of the probe 2 are sent to the AD converter 51 via the resistors R3 and R4 and to the differential amplifier 52 via the switches S2 and S3. Entered.

  The AD converter 51 is connected to a control signal processing circuit 53 and a differential amplifier 52, and the control signal processing circuit 53 is connected to a resistance value output circuit 54. A digital signal is output from the control signal processing circuit 53, and an analog signal is output from the resistance value output circuit 54. The control signal processing circuit 53 is connected to the switch group 55 via the switching line group 56. The switch group 55 is connected to the differential amplifier 52.

  In order to easily detect a minute temperature difference signal from the first sensor 25 and the second sensor 26, it is preferable that the AD converter 51 has high accuracy and high resolution. The resistors R1, R2, R3, and R4 are high precision resistors. Vref is a reference voltage of the AD converter 51 and is a full scale value of the AD conversion value.

  As shown in FIG. 3, the probe 2 in the proposed ear-type body temperature measuring device includes a main body part 21, a temperature measuring part 22 connected to the main body part 21, and a tab 23 provided along the outside of the main body part 21. including. The main body 21 is formed in a cylindrical body that is bent in a substantially L shape, which includes a long side portion 211 and a bent short side portion 212. A long side portion 211 extends from below the ear hole 9 a of the temperature measuring subject 9 along the vicinity of the face temple, and a bent short side portion 212 is coupled to the flange portion 221 of the temperature measuring unit 22. This generally L-shaped shape directs the distal end portion 222 of the temperature measuring portion 22 toward the eardrum in the ear canal 9a of the temperature measuring subject 9, and prevents the main body portion 21 from falling off the auricle or rotating on the auricle when worn. To. The cable 3 extends from the lower end of the main body 21, and the flexible printed circuit board 246 equipped with the first sensor 25 and the second sensor 26 is electrically connected to the male connector 4. The tab 23 is provided to facilitate work when the probe 2 is attached to and detached from the ear hole 9a of the temperature measuring subject 9.

  The main body 21, the temperature measuring unit 22, the tab 23, and the sensor mirror 24 constituting the probe 2 are made of a heat insulating material. The temperature measuring unit 22 is preferably covered with an elastomer or silicone rubber in consideration of the allergic constitution of the temperature measuring subject 9. The sensor mirror (point light source condensing sensor mirror) 24 is made of an insulating material. A protective cover 27 that covers the front surface of the sensor mirror 24 is provided.

  In measuring the body temperature, first, the first sensor 25 and the second sensor 26 are temperature calibrated simultaneously. In this temperature calibration, the body temperature of the temperature measuring subject 9 is measured using the measuring apparatus body 5 shown in FIG. First, the probe connector 4 is connected to the measuring apparatus body 5 and the temperature plug 7 is connected to the monitor 8.

a) Offset calibration Switch S1 of switch group 55 is turned on, and switches S2 and S3 are turned off. A / D conversion is executed to obtain an offset value. Since the resistors R1 and R2 are known, the AD input value is known. The difference between the AD conversion value and the AD input value is an offset error of the differential amplifier 52 and the AD converter 51. The AD converter input V1 at the time of offset calibration is R2 / (R1 + R2) × Vref. In the case of a high-precision AD converter, since self-calibration is performed for each measurement, the offset error of the AD converter may be ignored. Accordingly, the offset error is substantially due to the differential amplifier 52.

b) Measurement of the first sensor 25 The switch S2 is turned on and the switches S1 and S3 are turned off. A / D conversion is executed to obtain an A / D conversion value. The AD conversion input V2 at the time of measurement by the first sensor 25 is R3 / (R3 + RTh1) × Vref. However, RTh1 is the resistance value of the first sensor 25 at an arbitrary temperature.

c) Measurement of second sensor 26 Switch S3 is turned on and switches S1 and S2 are turned off. A / D conversion is executed to obtain an A / D conversion value. The AD conversion input V3 at the time of measurement by the second sensor 26 is R4 / (R4 + RTh2) × Vref. However, RTh2 is the resistance value of the second sensor 26 at an arbitrary temperature.

d) AD conversion value difference between the first sensor 25 and the second sensor 26 The offset value obtained by offset calibration is subtracted from the AD conversion value of the first sensor 25. From the relationship between this value and the difference between the AD conversion values of the first sensor 25 and the second sensor 26, the temperature of the target point to be measured is obtained.

  The measured temperature data is output as a digital signal from a control signal processing circuit 53 that is an MCU (microcontroller), and an analog signal is output from the resistance value output circuit 54. The analog temperature resistance value is an output for displaying the temperature on the monitor 8 of the thermistor thermometer.

  The analog signal of the measured resistance value corresponding to the temperature is converted into a digital signal indicating the temperature value by the control signal processing circuit 53 and output to the resistance value output circuit 54. The resistance value output circuit 54 has the configuration shown in FIG. 4 and is an 11-digit analog-digital conversion circuit that converts a digital signal of temperature value into an analog resistance value for the thermistor thermometer and outputs the analog resistance value.

  In the resistance value output circuit 54 of FIG. 4, resistors with an accuracy of 0.1% are selected for the resistors R19, R20, and R21. AN0 to AN10 are analog switches. These analog switches operate with a single power supply of 3V. The resistance values of the resistors R9 and R10 of the bias voltage circuit 542 are R9 = R10, and a bias voltage of 1.5 V is applied to each of the analog switches AN0 to AN10.

  P0 to P10 are port outputs of the control signal processing circuit 53 formed of an MCU and perform on / off control of the analog switches AN0 to AN10. The ports P0 to P10 are 1 (HIGH), the analog switches AN0 to AN10 are open (OFF), the ports P0 to P10 are 0 (LOW), and the analog switches AN0 to AN10 are closed (ON). The ports P0 to P10 output the resistance value in binary. If the resistance values of the analog switches AN0 to AN10 are ignored, the resistance value Rout between the resistance value output terminals A and B becomes the binary resistance value itself written in the ports P0 to P10.

  That is, when an 11-digit on / off digital signal is output from the ports P0 to P10 of the control signal processing circuit 53, the corresponding analog switches AN0 to AN11 are opened (off) at 1 (HIGH), Close (ON) with 0 (LOW). As a result, the serial combined resistance value of the digit resistor Ri opened by the analog switch ANi is converted into a resistance value Rout corresponding to the digital signal of the temperature value.

  The monitor 8 uses the output resistance value Rout as the resistance value output from the thermistor thermometer, and further displays the temperature by resistance value / temperature conversion.

  FIG. 5 shows the temperature / resistance characteristic of the thermistor thermometer. This characteristic graph is stored as a table. Now, when the on-resistance values of the analog switches AN1 to AN10 are set to zero and the temperature measurement value is 35 ° C., the resistance value to be obtained is 1471Ω with reference to the characteristic graph of FIG. Since the resistor R11 of the lowest analog switch AN0 is 2Ω, it is sufficient to output 1471/2 = 735 to the analog output circuit of FIG. Specifically, the decimal number 735 is 2DF (01011011111) in binary expression, and 2 + 4 + 8 + 16 + 32 + 128 + 256 + 1024 = 1470 (Ω) is obtained by outputting the binary signal to the ports P0 to P10 as they are. Therefore, the control signal processing circuit 53 outputs the upper 10-digit binary resistance value signal “01011011111”, and the resistance value output terminals A and B output the corresponding resistance value output Rout of 1470Ω.

  The measuring device body 5 is intended to continuously measure the temperature to be measured over a long period of time, and the operation procedure includes (1) calibration, (2) measurement of the first sensor 25, and (3) second sensor. 26 measurements, (4) measurement temperature calculation, and (5) temperature data output. The operation procedures (1) to (5) are repeated continuously.

  The monitor 8 performs resistance value / temperature conversion output from the thermistor thermometer on the input analog temperature resistance value, and displays the obtained temperature value.

  Thus, according to the ear-type body temperature measuring device that has been proposed in recent years, an ear-type body temperature measuring device that can continuously perform ear-type body temperature measurement and obtain an accurate body temperature measurement result can be realized.

  The ear-type body temperature measuring apparatus according to one embodiment of the present invention will be described below as it relates to the improvement of the proposed ear-type body temperature measuring apparatus of the present invention. The ear-type body temperature measuring device of the present embodiment is characterized by the configuration of the resistance value output circuit 54A in the measuring device main body shown in FIG.

  In the case of the resistance value output circuit 54 employed in the proposed ear-type body temperature measuring device, it is designed on the assumption that each of the 11 resistors Ri has an ideal resistance value. For example, the first digit resistor R11 is designed to be 2Ω, the tenth digit resistor R12 is 1024Ω, and the eleventh digit resistor R21 is 2048Ω. However, at the production site, it is not easy to give the resistance element an ideal resistance value, and if an attempt is made to give the ideal resistance value, it becomes expensive. Therefore, it is desirable that the resistance value of the resistor can be realized by a value corresponding to a standard number sequence (IEC 60063 or JIS C5063). This is because it is commercially available and can be obtained relatively easily, and the cost can be reduced.

  However, in the case of commercially available resistance elements that can be easily obtained, there is an error in the actual resistance value for each resistance element, even if the resistance elements are displayed with the same resistance value. Deviation occurs. For example, the resistance R110 of the resistance value output circuit 54A shown in FIG. 6 is 1020Ω, and there is a deviation of −0.39% compared to the resistance R10 = 1024Ω of the resistance value output circuit 54 of the first embodiment. With the resistance values of the circuit of FIG. 6, the target accuracy cannot be achieved if binary values are output directly to the ports P0 to P10. Therefore, even if the apparatus cost can be reduced by adopting the internal circuit of the body temperature measuring apparatus used in the medical field, the temperature accuracy cannot satisfy the requirement. Further, the on-resistance values of the analog switches AN0 to AN10 may not be ignored.

  The ear-type body temperature measuring device according to the present embodiment has been invented in view of the current situation at the production site. In the present embodiment, since the other configuration of the resistance value output circuit 54A is the same as that of the proposed ear body temperature measuring device, hereinafter, the same reference numerals are used for the same elements, and An ear body temperature measuring device according to an embodiment will be described.

  The resistance value output circuit 54A in the ear-type body temperature measuring device of the present embodiment converts the digital resistance value input into an analog resistance value for the thermistor thermometer and outputs it. That is, when an 11-digit digital resistance value corresponding to the temperature measurement value is output from the control signal processing circuit 53 formed of a microcontroller (MCU), this is also input to the digital resistance correction circuit 541 in the MCU. Then, the 11-digit on / off signal corrected by the digital resistance correction circuit 541 is output to the ports P0 to P10 corresponding to the 11 analog switches AN0 to AN11, respectively.

  The resistance value output circuit 54A includes a bias voltage circuit 542 similar to the proposed ear-type body temperature measuring device, and 11 analog switches AN0 to AN10 that are opened / closed by an 11-digit corrected on / off signal. N resistors R101 to R111, each of which is connected in parallel to each of these 11 analog switches AN0 to AN10 and connected in series so as to be in series, have N resistances. Analog resistance value output terminals A and B commonly connected to the analog switches AN0 to AN10 and the resistors R101 to R111. The bias voltage circuit 542 is for applying a bias voltage to the analog switches AN0 to AN10.

  The digital resistance value correction circuit 541 has the configuration shown in FIG. 7, and the resistance of the digital resistance value input unit 544 that inputs the digital resistance value SD1 corresponding to the temperature measurement value from the control signal processing circuit 53 and the resistance value output circuit 54A. The resistance value data storage unit 545 that stores the actual resistance values of R101 to R111, the resistance value data in the resistance value data storage unit 545 is referred to the digital resistance value SD1 input by the digital resistance value input unit 544, A correction resistance value calculation unit 546 for obtaining an analog switch signal SD2 obtained by combining on / off of 11-digit analog switches AN0 to AN10 for realizing an analog resistance value corresponding to the digital resistance value, and a correction resistance value calculation unit 546 Analog switch signal combining ON / OFF of 11 digit analog switch AN0-AN10 And a analog switch signal output unit 547 which outputs SD2 to the port P0 to P10.

  In the resistance value output circuit 54A of the present embodiment shown in FIG. 6, when the actual resistance values of the resistors R101 to R111 are different from the ideal values, the input digital resistance value is changed to an 11-digit binary value. Even if the analog switch of each digit is turned on / off corresponding to the binary value of the digit, an ideal desired resistance value cannot be obtained.

  An ideal combination of 11 resistance values for outputting an 11-digit digital resistance value is the resistance R11 to R11 adopted in the resistance value output circuit 54 of FIG. 4 adopted in the proposed ear-type body temperature measuring device. Let R21 be assumed. That is, it is assumed that the first digit is 2Ω, the second digit is 4Ω,..., The eleventh digit is 2 11 Ω = 2048Ω. The resistance groups R101 to R111 that can be used in the actual resistance value output circuit 54A are deviated from the ideal resistance values as shown in FIG. 6, and the first digit is 2Ω and the second digit is 3.9Ω. ,..., Suppose that the eleventh digit is 2050Ω. Here, if the 11-digit digital resistance value SD1 is “01011011111” = 735 (decimal number) × 2Ω, the ideal resistance value output circuit 54 shown in FIG. The analog switches AN5, AN8, AN10 corresponding to the digit 0 are turned on (closed) to bypass the resistors R16, R19, R21, and the series combined resistance value Rout = 1470Ω (2Ω + 4Ω + 8Ω + 16Ω + 32Ω + 128Ω + 256Ω + 1024Ω) is obtained between the A and B terminals. It was.

  On the other hand, in the case of the present embodiment, if the combination is similar to the above, the series combined resistance value is Rout = 1463.7Ω (2Ω + 3.9Ω + 8.2Ω + 16Ω + 31.6 + 127Ω + 255Ω + 1020Ω), which is an ideal resistance value. Gives a difference of -6.3Ω. Even when the on-resistance value of the analog switch is 0.35Ω and the on-resistance value of the switch is taken into account, a difference of −5.25Ω is obtained.

  Therefore, in the case of the present embodiment, the corrected resistance value calculation unit 546 refers to the resistance value data in the resistance value data storage unit 545 corresponding to the input digital resistance value SD1, and the series combined actual resistance value is the input digital resistance value SD1. The analog switch that forms a pair with the energizing resistance element is turned off (1 = HIGH), and the analog switch that is bypassed by the analog switch is turned on (0 = LOW). The analog switch signal SD2 is combined, and the analog switch signal output unit 547 outputs the analog switch signal SD2 to the ports P0 to P10 as a pseudo 11-digit binary signal (1/0 signal).

  In the case of the above example, assuming that the on-resistance value of each of the analog switches AN0 to AN10 is 0.35Ω, an 11-digit parallel analog switch signal SD2 is obtained by the following calculation. That is, when the temperature measurement value is 35 ° C., the resistance value obtained from FIG. 5 is 1471Ω, and this digital resistance value is input as an output command.

  (1) When the resistance value when all the analog output circuits are set to 0 (all on) is obtained, there are 11 analog switches AN0 to AN10, so that 0.35 × 11 = 3.85Ω. Therefore, 1471Ω−3.85Ω = 1467Ω is obtained.

  (2) This 1467Ω is compared with the most significant digit resistor R111 = 2050Ω. Since 1467Ω <2050Ω, the port output P10 of the most significant digit is “0”.

  (3) Similarly, compare 1467Ω with the tenth digit resistor R110 = 1020Ω. Since 1467Ω> 1020Ω, the 10th digit port output P9 is “1”. The remaining resistance value is 1467Ω-1020Ω = 447Ω.

  (4) The remaining resistance value 447Ω is compared with the ninth digit resistance R109 = 511Ω. Since 447Ω <511Ω, the 9th digit port output P8 is “0”.

  (5) Subsequently, the resistance value 447Ω is compared with the eighth digit resistance 108 = 255Ω. Since 447Ω> 255Ω, the port output P7 of the eighth digit is “1”. The remaining resistance value is 447Ω−255Ω = 192Ω.

  (6) The remaining resistance value 192Ω is compared with the seventh digit resistance R107 = 127Ω. Since 192Ω> 127Ω, the seventh-digit port output P6 is “1”. The remaining resistance value is 192Ω-127Ω = 65Ω.

  (7) The remaining resistance value of 65Ω is compared with the sixth digit resistance R106 = 63.4. Since 65Ω> 63.4Ω, the sixth-digit port output P5 is “1”. The remaining resistance value is 65Ω-63.4Ω = 1.6Ω.

  (8) The remaining resistance value of 1.6Ω is compared with the fifth digit resistance R105 = 31.6Ω. Since 1.6Ω <31.6Ω, the fifth-digit port output P4 is “0”.

  (9) The remaining resistance value of 1.6Ω is compared with the fourth digit resistance R104 = 16Ω. Again, since 1.6Ω <16Ω, the fourth-digit port output P3 is also “0”.

  (10) The remaining resistance value of 1.6Ω is compared with the third digit resistance R103 = 8.2. Again, since 1.6Ω <8.2Ω, the third-digit port output P2 is also “0”.

  (11) The remaining resistance value of 1.6Ω is compared with the second digit resistance R102 = 3.9. Again, since 1.6Ω <3.9Ω, the second-digit port output P1 is also “0”.

  (12) The remaining resistance value of 1.6Ω is compared with the first digit resistance R101 = 2. Again, since 1.6Ω <2Ω, the first-digit port output P0 is also “0”.

  Through the above processing, the analog switch signal SD2 that is a combination of ON / OFF of the analog switches AN0 to AN10 for finally realizing the output resistance value corresponding to the input resistance value 1471Ω becomes “0101110000000”. At this time, the combined resistance value is 0.35Ω + 1020Ω + 0.35Ω + 255Ω + 127Ω + 63.4Ω + 0.35Ω + 0.35Ω + 0.35Ω + 0.35Ω + 0.35Ω = 1467.85Ω. Thereby, the difference of −5.25Ω from the ideal resistance value can be improved to −3.15Ω.

  In this way, the 11-digit parallel analog switch signal SD2 obtained by the digital resistance value correction circuit 541 is output to the analog switch groups AN0 to AN10 of the resistance value output circuit 54A shown in FIG. As in the case of the proposed ear body temperature measuring device, the analog switches AN0 to AN11 are opened (off) by 1 (HIGH) and closed (on) by 0 (LOW). As a result, the series combined resistance value of the digit resistor Ri with the analog switch ANi opened is output as the analog resistance value Rout for the thermistor thermometer corresponding to the temperature measurement value.

  The monitor 8 uses the resistance value output Rout as the temperature resistance value of the thermistor thermometer, and displays the temperature by resistance value / temperature conversion with reference to a characteristic graph equivalent to the graph of FIG. 5 or a converted value data table.

  In the present embodiment, the on-resistance values of the analog switches A0 to AN10 are also taken into consideration. However, when it is necessary to simplify the device, it is possible to adopt a configuration in which the on-resistance value is not taken into consideration.

  However, in order to increase the accuracy, it is preferable to consider the on-resistance value of the analog switch. For example, when the analog switches AN0 to AN9 are turned on and only the analog switch AN10 is turned off, the resistance value of the entire resistance value output circuit 54A in FIG. 6 is 2050Ω + 0.35Ω × 10 = 2053.5Ω, and +0.17 % Error. This is because the influence of the ON resistance values of the analog switches AN0 to AN10 is + 0.17% at the maximum.

  As for the resistance value of the analog switch, an average value of 1 can be stored as in the above calculation example. More strictly, the individual on-resistance values of the analog switches AN0 to AN10 are stored. It can also be left. However, in the latter case, since the improvement in accuracy is not so conspicuous as the amount of correction calculation by the MCU increases, it is not realistic, so either one is adopted depending on the application.

  In addition, the resistance values and transistor characteristic values in the above embodiments are exemplifications, and are not limited to those numerical values, and are appropriately determined according to specifications such as the use, size, and scale of the device. It can be changed.

It is schematic structure explanatory drawing of the ear-type body temperature measuring apparatus proposed in recent years. It is a schematic circuit block diagram of the said ear-type body temperature measuring apparatus proposed. It is a partially broken side view of the probe constituting the proposed ear body temperature measuring device. The circuit diagram of the resistance value output circuit part in the said ear-type body temperature measuring apparatus proposed. The graph which shows the temperature-resistance value characteristic of the thermistor thermometer used in the said ear-type body temperature measuring apparatus proposed. The block diagram of the resistance value output circuit in the ear-type body temperature measuring device of one embodiment of this invention. The block diagram of the digital resistance value correction circuit in the resistance value output circuit in the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ear body temperature measuring device 2 Probe 3, 6 Cable 4 Male connector 5 Measuring device main body 9 Temperature measuring person 9a Ear hole 21 Main body part 22 Temperature measuring part 23 Tab 24 Sensor mirror 25 First sensor 26 Second sensor 27 Protective cover 53 Control signal processing circuit 54A Resistance value output circuit 541 Digital resistance value correction circuit 542 Bias voltage circuit 544 Digital resistance value input unit 545 Resistance value data storage unit 546 Modified resistance value calculation unit 547 Analog switch signal output unit MCU Microcontroller SD1 Digital resistance value SD2 Analog switch signal Rout Resistance value output A, B Resistance value output terminal

Claims (4)

N analog switches that are turned on / off by a 1 (HIGH) / 0 (LOW) signal of each digit of an input N digit (N is an arbitrary natural number) binary signal;
N resistors connected in parallel to each of the N analog switches and connected in series so that all of them are in series;
An actual resistance value storage unit for storing actually measured resistance values of the N individual resistors;
An analog resistance value output terminal commonly connected to the N analog switches and resistors;
A temperature command input unit for inputting an output temperature command;
A temperature / resistance value correspondence storage unit for storing a correspondence relationship between the temperature value and the resistance value output by the thermistor thermometer;
Corresponding to the output temperature command with reference to the correspondence relationship between the temperature value in the temperature / resistance value correspondence storage unit and the resistance value output from the thermistor thermometer with respect to the output temperature command input by the temperature command input unit and temperature resistance value calculating unit obtains the output should do resistance value of the thermistor thermometer, you output binary code N digits representing the resistance value,
Rather than deciding whether to turn on / off the corresponding analog switch of the N analog switches according to the binary code 1 or 0 of each digit of the N-digit binary code output from the temperature resistance value calculation unit. The resistance value to be output by the thermistor thermometer corresponding to the output temperature command obtained by the temperature resistance value calculation unit with reference to the actually measured resistance values of the N individual resistances stored in the actual resistance value storage unit The N-digit binary code corresponding to is input, and a combination of a plurality of resistors is obtained such that the combined resistance value matches the resistance value represented by the N-digit binary code . Each of the N analog switches is turned on / off so that a combination can be realized, and an N-digit 1 (HIGH) for turning on / off the N analog switches. / 0 and an output resistance value calculation unit for outputting the (LOW) signal,
The output resistance value calculator is
A digital resistance value input unit for inputting and processing an N-digit binary code from the temperature resistance value calculation unit;
The resistance value represented by the N digit binary code input by the digital resistance value input unit is referred to the actually measured resistance value of each of the N resistors stored in the actual resistance value storage unit, and the N digit binary code is referred to. A modified resistance value calculation unit for obtaining an analog switch signal combining ON / OFF of the N analog switches in order to realize an analog resistance value corresponding to the resistance value represented by:
A resistance value output comprising: an analog switch signal output unit for outputting the N-digit 1 (HIGH) / 0 (LOW) signal corresponding to the analog switch signal obtained by the corrected resistance value calculation unit circuit. The actual resistance value storage unit stores measured resistance values of the N individual resistors and resistance values of the N analog switches,
The modified resistance value calculation unit in the output resistance value calculation unit refers to the actually measured resistance values of the N individual resistors stored in the actual resistance value storage unit and the resistance values of the N analog switches, Finding a combination of a plurality of resistors such that the resistance value to be output of the thermistor thermometer corresponding to the output temperature command obtained by the temperature resistance value calculation unit is a series combined resistance value. 2. The resistance value output circuit according to claim 1, wherein an analog switch signal obtained by combining ON / OFF of each of the N analog switches is obtained so that a combination of resistors can be realized. A measuring device main body having a built-in battery as a power source; and a temperature measuring probe connected to the measuring device main body in a state of being detachable by a connector, and controlling a temperature sensor of the temperature measuring probe in the measuring device main body. And a microcontroller that inputs a resistance value output signal corresponding to the measured temperature from the temperature sensor, converts the resistance value output signal into a temperature resistance value, and outputs the resistance value that the temperature resistance value from the microcontroller outputs from the thermistor thermometer In the ear-type body temperature measuring device with a built-in resistance value output circuit that reconverts and outputs to
The resistance value output circuit is:
N analog switches that are turned on / off by a 1 (HIGH) / 0 (LOW) signal of each digit of an input N digit (N is an arbitrary natural number) binary signal;
N resistors connected in parallel to each of the N analog switches and connected in series so that all of them are in series;
An actual resistance value storage unit for storing actually measured resistance values of the N individual resistors;
An analog resistance value output terminal commonly connected to the N analog switches and resistors;
A temperature command input unit for inputting an output temperature command;
A temperature / resistance value correspondence storage unit for storing a correspondence relationship between the temperature value and the resistance value output by the thermistor thermometer;
Corresponding to the output temperature command with reference to the correspondence relationship between the temperature value in the temperature / resistance value correspondence storage unit and the resistance value output from the thermistor thermometer with respect to the output temperature command input by the temperature command input unit and temperature resistance value calculation unit obtains the output should do resistance value of the thermistor thermometer, and outputs a binary code N digits representing the resistance value,
Rather than deciding whether to turn on / off the corresponding analog switch of the N analog switches according to the binary code 1 or 0 of each digit of the N-digit binary code output from the temperature resistance value calculation unit. The resistance value to be output by the thermistor thermometer corresponding to the output temperature command obtained by the temperature resistance value calculation unit with reference to the actually measured resistance values of the N individual resistances stored in the actual resistance value storage unit The N-digit binary code corresponding to is input, and a combination of a plurality of resistors is obtained such that the combined resistance value matches the resistance value represented by the N-digit binary code. Each of the N analog switches is turned on / off so that a combination can be realized, and an N-digit 1 (HIGH) for turning on / off the N analog switches. / 0 and an output resistance value calculation unit for outputting the (LOW) signal,
The output resistance value calculator is
A digital resistance value input unit for inputting and processing an N-digit binary code from the temperature resistance value calculation unit;
The resistance value represented by the N digit binary code input by the digital resistance value input unit is referred to the actually measured resistance value of each of the N resistors stored in the actual resistance value storage unit, and the N digit binary code is referred to. A modified resistance value calculation unit for obtaining an analog switch signal combining ON / OFF of the N analog switches in order to realize an analog resistance value corresponding to the resistance value represented by:
And an analog switch signal output unit that outputs the N-digit 1 (HIGH) / 0 (LOW) signal corresponding to the analog switch signal obtained by the corrected resistance value calculation unit. measuring device. The actual resistance value storage unit stores measured resistance values of the N individual resistors and resistance values of the N analog switches,
The modified resistance value calculation unit in the output resistance value calculation unit refers to the actually measured resistance values of the N individual resistors stored in the actual resistance value storage unit and the resistance values of the N analog switches, Finding a combination of a plurality of resistors such that the resistance value to be output of the thermistor thermometer corresponding to the output temperature command obtained by the temperature resistance value calculation unit is a series combined resistance value. The ear-type body temperature measuring device according to claim 3, wherein an analog switch signal obtained by combining on / off of each of the N analog switches is obtained so that a combination of resistors can be realized.

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