DE2746004A1 - Electrical clinical thermometer giving rapid reading - uses algorithm to determine asymptotic end point from two successive temp. readings - Google Patents

Abstract

An electrical clinical thermometer is used to give a rapid reading. It operates using a given algorithm, so that the asymptotic point of a temperature measurement can be indicated by taking two readings as the temperature rises. A transducer (20) such as a thermistor delivers a signal by way of a Celsius/Fahrenheit switch (28) to a temperature/frequency A/D converter (30). The measuring time interval (C) is determined by a logical flip-flop circuit (42). The counter (34) output passes by way of an intermediate store (16) and a multiplexer (48) to an LED indicator device (50).

Description

Description introduction

The tendency to electrify physical measuring devices continues has recently also made its way into the medical field. Electronic timepiece for measuring the pulse, strong acoustic amplifiers for listening to the fetal heart and electronic temperature measuring devices are already in widespread use. One such electronic temperature measuring device is already the subject of the US application No. 392,961 of the same applicant, entitled "Electronic Temperature Computer", in which a relatively cheap thermistor and an electronic lead circuit for quickly measuring a patient's temperature.

Although many of these known systems operate digitally, theirs allow Components and circuit elements are not the often desirable ones at the same time high speeds and miniaturization. Mostly it is necessary discrete components and discrete logical elements in design and manufacture to use these advanced medical electronic circuits. Because of Due to the limited space available, it is not always possible to obtain the desired Include number of functions in a single arrangement.

Based on this knowledge, it is an object of the invention to provide a to create improved thermometers using digital techniques. It should measure the temperature in a short time and the measured value either in degrees Celsius or give Fahrenheit. Finally, in the temperature meter according to the invention inexpensive thermistors and readily available electronic components use Find.

The object is achieved according to the invention in accordance with the main claim by means for measuring the temperature with a temperature-responsive element, by means for converting the measured values determined in a first and in a second predetermined, discrete point in time into signals with a variable, measured by the Temperatures determined pulse frequency, by counting means, according to the algorithm respond to the signals by means for visual digital display of the meter's readings and by control means electrically connected to the transducer and selectively enabling the transducer at predetermined first and second times and electrically connected to the counting means for control thereof, so that they count the pulses of the signals with a variable pulse frequency according to the algorithm, where in the above formula TF denotes the final temperature to be measured, T1 the temperature measured first, T2 the temperature measured as the second, 1t the time difference between the first and second measurement ,? a thermal time constant that depends on the temperature-sensitive element and e is the base of the natural logarithm.

The invention shows an electronic device for use with an electronic thermometer to display a final temperature only two measurements need to be made. The invention is for use in medical temperature measurements and especially for use in a thermistor probe, which is introduced to the patient, suitable. The electronic thermometer is working due to an algorithm based on the response curve of a typical thermistor is based. The algorithm requires that two measurements be made for certain periods of time and, equally important, to be done at critical, predetermined times.

The invention provides the apparatus employing this algorithm the ability to display temperatures in both Fahrenheit and Celsius. It also provides a device that can operate on a low battery voltage and, more importantly, the invention discloses special counting and logical Circuits that adjust the algorithm to the best possible Way to perform. Furthermore, the invention makes use of readily available commercially available electronic ones Parts for counting and displaying the patient's actual body temperature.

DESCRIPTION OF THE FIGURES An exemplary embodiment of the invention is shown in FIG Drawing shown and is described in more detail below. 1 shows a characteristic curve of the response of a typical thermistor temperature meter to the temperature, the temperature being plotted against time, FIG. 2 Block diagram of a preferred embodiment of the temperature measuring device according to the invention, FIG. 3 is a schematic circuit diagram of a Celsius / Fahrenheit switch, as used in the device according to FIG. 2 and FIG. 4 shows a functional diagram of the logical linking element used in the device according to FIG (Gate Logic element).

Fig. 1 shows a typical response curve of a commercially available one Thermistor temperature meter. On the ordinate axis T is the temperature and on the abscissa axis t the time plotted. The real one Response curve 10 is generally an exponential curve, although it is not necessarily must be an exact exponential curve. Since it is the object of the invention to use of relatively inexpensive and easily available thermistors to enable these thermistors will naturally not be able to take accurate measurements to undertake a wide temperature range. Because the response of the thermistor cannot fall below a certain value, which is referred to as the threshold value TR the threshold will never quite reach the true final temperature, TF,, but only approach it.

In the above patent application it is shown that only two Measurements at predetermined times for precise and quick prediction of the final value of TF are required. These appropriately placed measurements will be shown as T1 at t1 and as T2 at t2. Knowing the specific times To which the measurements have to be made is also the knowledge of the period at required between the two times. From the aforementioned US application goes also shows that the value of as a function of the thermal response constant t of the thermistor used. This is done according to the formula a t = ln 2 (1) Assume the typical thermal response constant is 20, then equation (1) gives a t of approximately 14 seconds. These Time is short enough to be used in the invention. Though for the invention the speed is of great importance, it is not always advantageous take the first measurement too soon after inserting the probe into the patient.

Referring to Figure 2, there is a block diagram of a preferred embodiment of the invention shown. The thermistor probe inserted into the patient's body 20 generates at their outputs 22, 24 and 26, which with the Celsius / Fahrenheit (C / F) Switch 28 are connected, a corresponding change in resistance. The C / F switch 28 is electrically connected to a temperature-frequency analog-digital converter 30, which is shown in detail in FIG. The A / D converter 30 converts the the temperature-dependent analog voltage generated by the change in resistance is generated into a digital signal, which now has the temperature information, which is expressed as the pulse frequency. The core of the A / D converter 30 forms an oscillator whose period of oscillation is determined by the resistance of the probe 20 located thermistor is controlled.

The digital signal that now contains the temperature information in its pulse frequency contains, is on line 32 a conventional up / down Decade counter 34 supplied.

The decade counter 34 is by a signal on the line 36 of the power switch 38 is cleared or reset each time the device is used should be, i.e.

when the power switch 38 is operated. How the up / down work Decade counter 34 is activated by an up / down control signal on the line 40 controlled, which is generated by a logical linking element 42.

The logical connection element 42 is in its details in Fig. 4 shown.

Since the invention is based on equation (1) to produce an approximation the temperature, the time between the two temperature measurements (, t) being controlled. The temperature-frequency converter is activated at certain times one generated by the logic combination element 42 and passed via the line 44 Signal released. From the aforementioned patent application it is apparent that the obtained End temperature twice the second temperature measurement (T2> minus the first Temperature measurement (T1) is. Since T1 appears first, in order to subtract it, the Counter 34 first set to count down by an instruction on line 40. That Logical linking element 42 then generates a release signal on the line 44 and T1 are input to counter 34 via line 32. To double Value of T2 enter and, since the temperature by a continuous Pulse current is reproduced, it is only necessary to pass the signal over the line 32 to be entered in the counter 34 for a time that is twice as large as the time while the T1 was entered. A period of one second for T1 and two Seconds for T2 gives satisfactory results.

Therefore, if the signal on the line 44, the converter 30 for a Period of two seconds releases, the downward control signal must be on the line 40 give the counter 34 the command to count up. Then the counter 34 becomes a Number of pulses received that are twice as large as the second temperature reading minus the first temperature measurement.

The content of the counter 34 is then stored in parallel in a conventional buffer 46 and a multiplexer 48 input.

The multiplexer 48 serves to reduce the power consumption required for operation of the light emitting diode (LED) display 50 is required, on a per se known Way to decrease. After the counter contents in a conventional decoder 52 has been decoded, it is indicated by the LED display 50. An oscillator 54 and a digit selector 56 serve as a display control device and are connected to the MuXtiplexer 48 connected by a line 58. Counter 34, memory 46, multiplexer 48, decoder 52, oscillator 54 and digit selector 56 are commercially available as simple integrated, by the dashed line 60 indicated circuit available. It is known, how these functional elements are connected to pulse signals and display the information contained in the pulse signals.

As the preferred embodiment of the invention is body temperature of a person is to measure and display, the display must be able to display numbers, that are greater than ninety-nine. However, the hundred display only has to be one Show one and, since low power consumption is important and not necessary is to display a temperature as "098.6", the invention provides a means that clears the hundred digit unless it shows a one.

A greater-than-one hundred indicator 62 is with the most significant digit signal with line 64 from a decoder 66 and with line 58 from the dialer 56 connected. The greater-than-one hundred indicator 62 is made by a logical link which generates an enable signal on line 66 to the hundreds digit only to be released if a one must be displayed and not to be released, to prevent a zero from being displayed.

To avoid false readings due to low voltage it is a battery indicator 68 is provided. The battery indicator 68 can be a parity checker be that the internal bias voltage Vcc of a line 70 with a fixed Voltage drop in a diode or the like compares.

The battery indicator also has an input that is connected to the Output of the display control device is connected via a line 72 and an output 74, which is connected to all decimal points in the LED display 50. When the tension falls below a predetermined value on line 70, the display controller through line 72, indicator 68 and output 74 with all decimal points connected in the display 50, which are continuously illuminated and thereby the Make operating personnel aware that the battery voltage is a linear value has fallen below.

In the preferred embodiment of the invention it is desirable that the measurement prediction function is performed within thirty seconds. Also, as mentioned above, it is necessary to know the exact times at which the two temperature measurements are carried out.

Therefore, an accurate timer device is required. It is a quartz-controlled oscillator or timer 76 is provided, which via a line 77 generates a signal with a frequency of 2,097,152 oscillations per second. This 2,097,152 Hz signal is then fed to a 21-stage binary distributor 78 and thereby generates a series of timer pulses exactly 1.0 seconds long. These impulses will then have a Line 79 of a group of decade counters 80, which are shown in detail in FIG. The decade counter 80 are then connected by multiple lines 82 and across by the same signal the line 36, which is used to enable the counter 34, is released. Of the Timers 76, decade counters 80 and logical linking element 42 act together to create the internal timing that is necessary to control the temperature frequency Analog-to-digital converter 30 to enable the signal over the line 32 containing the predicted temperature value.

The logical linking element 42, which is shown in detail in FIG is generated in addition to the up / down command via line 40 to the counter 34 also the switch-off command, which is fed to the mains switch 38 via a line 84 will. This command is used to switch off the power to save battery 86, after a certain period of time has passed. Experience has shown that forty seconds is enough until the power is switched off. The logical link element 42 is also used to control a display on / off switch 88 which has an enable signal generated via a line 90 which is connected to the LED display decoder 52. This release signal is used to give a clear pulse to the decoder 52, so that the display does not show the rise in temperature but only the final one temperature to be displayed.

The logic combination element 42, the decade counter 80 and the Crystal controlled timers 76 also generate timing signals at preselected intervals. For example, a signal may be generated over line 92 after 30 seconds have passed are, and another signal may after 30 seconds have passed over the Line 94 are generated.

These signals can be used with indicator lights or buzzers used when measuring heart rate or other tasks that require accurate timing will.

In Fig. 3 the probe, Celsius-Fahrenheit switch and temperature-frequency Analog-to-digital converter shown in more detail. The probe 20 contains a single one Thermistor element 100 and has a direct output lead 22. The other output lead 110 of the thermistor is connected to two variable resistors 112 and 114, which for Calibration of the thermistor 100 are used. Two variable resistors are required because the thermistor is used for two separate temperature scales. The Celsius / Fahrenheit Switch 28 consists of a manually operated three-pole changeover switch 116. The A / D converter 30 is an oscillator whose oscillation frequency of R and C is dependent. In this case the resistance is changed. A conventional operational amplifier 120 is connected in a known manner so that it has a free swinging Multivibrator except that the thermistor probe 20 is inserted in the return path. Therefore, the oscillation frequency or pulse series changes with that of the thermistor 100 sensed temperature. Since the invention generates a signal that is a pulse number which shows a temperature in one of two different scales, the amplifier 120 must oscillate at two different frequencies. To do this reach, are in addition to the two variable resistors 112 and 114 in the return path two separate capacitors 122 and 124 through switch 116 to the amplifier 120 connected. The transducer 30 in Figure 2 is released, i.e. the operational amplifier 120 is caused to oscillate by an enable signal appearing on line 44. As mentioned above, this signal is generated by the logic combination element 42 and switches the oscillator on at a certain time for a second and later, again at a predetermined time for two seconds. The output of the oscillator is passed through a conventional amplifier 126 before going on the line 32 is fed to the up / down counter 34 of FIG.

In Fig. 4, the decade counter and the logic linkage element shown in detail. The 2,097,152 Hz signal is transmitted over line 77 from the quartz-controlled timer 76 in Fig. 2 fed to the binary distributor 78, which counts every 1.0 seconds, i.e. it generates a signal every 1.0 seconds line 78. This signal is fed to a decade counter 144 which is now counts in one-second intervals and a transmission signal every ten seconds generated via line 146. The timer signal then becomes the last decade counter 148 that counts at ten second intervals. The decade counters 144 and 148 and the binary distributor 78 are activated by the reset signal via the line 36 reset by the power switch. However, this reset signal is struck by the decade counters, because, as mentioned above, the power switch is switched off after 40 seconds. The decade counter 148 is then tapped at the digit four tap, and this signal becomes fed via a line 150 to an AND logic element 152, which is a part of the logical connection element forms. The second input to the AND link element 152 forms the bias voltage Vcc and, when both signals are present, becomes a Signal generated on line 84 which is used to turn off the power switch. As mentioned above, an enable signal to the temperature-frequency converter must be one second long after the expiration of 15 seconds and also for two seconds after the expiration of thirty seconds. These release signals must be in the line 44 reach the temperature-frequency converter 30 in FIG fed and are generated by a three-input AND logic element 154. In addition, there are three AND logic elements 156, 158 and 160, their Outputs are connected to the AND logic element 154. These AND logic elements 156, 158 and 160 have as inputs the various output taps from the Decade counters 144 and 148. These output taps are selected in a known manner, an output on line 44 at fifteen seconds, thirty seconds and generate thirty-one seconds. A release signal is required at thirty-one seconds to generate since the release signal lasts for two seconds must be present after thirty seconds have passed. To get the extra Generating timing signals over lines 92 and 94 is a double flip-flop 162 provided. As noted above, there is a signal on line 92 after fifteen Seconds available, which is achieved by one of the flip-flops with a Signal via line 164, which was generated by an AND logic element 166, is set.

This AND logic element 166 is with the decade counters 144 and 146 connected so that after the lapse of fifteen seconds there is an output signal generated. Likewise, the second half of the double flip-flop 162 goes straight through a signal from the decade counter 148 is set at ten second intervals counts after thirty seconds have passed. This thirty-second signal will also do the same on line 40 to the up / down decade counter 34 in FIG. 2 and is used as the up / down command signal. That is, according to the invention, it should be used for count down the second temperature measurement (T2) when it reaches thirty seconds, the signal on line 40 being that required signal.

The details of the above embodiment are only given as examples. Any type of thermistor probe and various other logic elements can be used and counters can be used.

Accordingly, the invention is not defined by the items given of the illustrated embodiment, with the exception of those who are determined by the claims.

Claims (19)

Title: Electronic measuring device for displaying an extrapolated Final temperature. Electronic measuring device for displaying an extrapolated final temperature, characterized by means for measuring the temperature with a temperature-responsive element, by means for converting the measured values determined in a first and in a second predetermined, discrete point in time into signals with a variable, measured by the Temperatures determined pulse frequency, by counting means, according to the algorithm respond to the signals by means for visual digital display of the meter's readings and by control means electrically connected to the transducer and selectively enabling the transducer at predetermined first and second times and electrically connected to the counting means for control thereof, so that they count the pulses of the signals with a variable pulse frequency according to the algorithm, where in the above formula TF denotes the final temperature to be measured, T1 the temperature measured first, T2 the temperature measured as the second, bt t the time difference between the first and second measurement, r is a thermal time constant that depends on the temperature-sensitive element and e is the base of the natural logarithm. 2. Apparatus according to claim 1, characterized in that the control means a crystal oscillator, decade counter electrically connected to the oscillator Counting the vibrations generated by the oscillator and a multitude of logical ones Linking elements comprise, with the counting means for generating output signals are connected after a certain number of pulses are counted by the decade counters became. 3. Device according to claim 1 or 2, characterized by means, those with the temperature measuring means and the converting means for controlling the variable Pulse frequency are connected so that the measured temperature is either in Fahrenheit or can be displayed in Celsius units. 4. Device according to one of the preceding claims, characterized by circuit means connected to the counting means and the display means are to selectively disable the most significant digit of the visual display, when the counting means contain a number below a certain size. 5. Device according to one of the preceding claims, characterized by an electrical power source and a power switch that is electrically connected to the Power source and the plurality of logical connection elements is connected to turn off the power source after the occurrence of a signal from the logic element. 6. Device according to one of the preceding claims, characterized through a voltage indicator associated with the power source and the visual Display means is connected to the display after the occurrence of a particular To illuminate the voltage value. 7. Apparatus according to claim 2 and one of the other claims, characterized by means associated with the plurality of logical linking elements and the display means are connected to the visual indication after the occurrence of a signal from the To make the link element ineffective. 8. Apparatus according to claim 2 and one of the other claims, characterized characterized in that the predetermined number of pulses after which the output signals fifteen pulses are generated by the large number of logic elements, includes thirty pulses and thirty-one pulses. 9. Apparatus according to claim 3 and one of the other claims, characterized characterized in that the means for controlling the variable pulse frequency is a Variety of variable resistors include, the measured temperature being either is given in Fahrenheit or Celsius units. 10. Device according to one of the preceding claims, characterized in that that the particular value corresponds to 100 degrees Fahrenheit. 11. The device according to claim 7, and one of the other claims, characterized by a binary distributor connected electrically between the crystal oscillator and the decade counter means is connected to turn the oscillator output into on to split the pulse signal occurring every second. 12. The device according to claim 8 and one of the other claims, characterized characterized in that the specific number of pulses after which the output signals are generated by the plurality of logical connection elements, further forty Includes impulses. 13. The device according to claim 12, characterized by an electrical Power source and a power switch that electrically connects to the power source and the multitude The logic linkage elements are connected to the power source after the occurrence of the output signal generated after the forty pulses ineffective. 14. The device according to claim 3 and one of the other claims, characterized characterized in that the converting means comprise an oscillator whose frequency is controlled by the temperature responsive element and that the control means electrical elements switchable for display in Fahrenheit or Celsius units and switching means to switch the alternative electrical elements alternatively to couple with the oscillator, the oscillator in alternative oscillation types oscillates to allow display in either Fahrenheit or Celsius units. 15. The device according to claim 14 and one of the other claims, characterized in that the means for measuring temperatures comprise a probe, which contains the temperature sensitive element and that some of the alternatives electrical elements are in the probe. 16. Device according to one of the preceding claims, characterized in that that the control means comprise means for generating at least one time signal, wherein the at least single time signal can be used for a function, the exact Requires timing. 17. The device according to claim 16, characterized in that the Means for generating at least one time signal. Means for generating at least a time signal after at least a predetermined time period. 18. Apparatus according to claim 16 or 17, characterized in that that the at least one predetermined period of time is a period of 15 seconds is. 19. Apparatus according to claim 16 or 17, characterized in that that at least a predetermined period of time is a period of 30 seconds.