JPS586140B2 - sokuonkei - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermometer and aims to shorten the required temperature measurement time.

In summary, the present invention shortens the required temperature measurement time by passing a relatively large current through the temperature measurement element to self-heat it until the temperature of the temperature measurement element approaches the temperature of the object to be measured.

FIG. 1 is a circuit diagram of an example of a thermometer to which the present invention is applied.

In the figure, a bridge circuit 5 is composed of resistors 1, 2, and 3 and a thermistor 4.

The thermistor 4 and the resistor 2 are connected and disconnected by a contact 9 of a relay 22.

The output of the bridge 5 is taken out to the display section 14 from terminals 7a and 7b.

A diode 15 connected in parallel with this output is for protecting the output from being subjected to a large voltage when the relay contact is on the 10 side.

12 is a constant voltage diode for stabilizing the voltage applied to the bridge circuit.

8 is a resistor for adjusting the bridge input, 13 is a resistor for adjusting the current of the constant voltage diode 12 and the bridge, 19
is an N-gate thyristor, 17 is a gate, 18 is an anode, 20 is a cathode, 16 is a resistor that determines the potential of the gate 17, and 24 and 25 are resistors that determine the anode potential.

22 is a latching type relay whose contacts are 9 and 10.
, 11.

23 is a capacitor, 26 is a switch, and 21 is a power supply to this circuit.

Next, the operation of this circuit will be explained.

By turning on the switch 26, the resistor 2 is connected to the capacitor 23.
5 and through the coil of relay 22 a charging current flows.

The relay 22 is operated by this charging current, and the relay contact is brought to the 10 side.

Then, the gate potential of the N-gate thyristor 19 becomes the potential determined by the resistor 16 and the temperature measuring thermistor 4.

On the other hand, the anode potential of the N-gate thyristor 19 is
4.25.

By bringing the thermistor 4 to the part to be measured, the temperature of the thermistor 4 increases and the resistance value decreases.

Then, the potential of the gate 17 of the N-gate thyristor 19 also decreases.

When the gate potential reaches the same value as the anode potential, the N-gate thyristor 19 suddenly becomes conductive, and the charge stored in the capacitor 23 is discharged via the relay coil 22.

This discharge activates the relay 22, and its contact becomes on the 9 side.

Here, once the N-gate thyristor 19 enters the conductive state, the resistance value is set to 2 to maintain that state until the measurement is completed.
I have to decide on 4, 25, and 16.

By placing the contact on the 9 side, the resistors 1, 2, and 3 and the temperature-detecting thermistor 4 constitute a regular temperature-detecting bridge circuit 5.

When the contact 9 is open, a large output is produced on the output side of the bridge circuit 5 due to its input impedance, so a diode 15 is placed in parallel with the bridge output to protect the input of the display section 14.

When the thermistor 4 becomes close to the body temperature and the display begins to appear, the output is in the reverse bias direction with respect to the diode 15, so it does not cause any error in the display.

In a circuit that performs such an operation, when the contact point is on the 9 side and forms a regular bridge circuit 5, the self-heating of the temperature-detecting thermistor 4 is minimized, and the thermistor 4 is
The error caused by the current flowing through the circuit must be minimized.

On the other hand, when the contact point is on the side 10, a current as large as possible is passed through the thermistor 4 to cause self-heating, thereby accelerating the temperature rise of the temperature-detecting thermistor 4.

That is, when the temperature of the thermometer is lower than the body temperature, the thermistor 4 self-heats to accelerate the temperature rise, and when the temperature approaches the body temperature, the current flowing through the thermistor 4 is reduced.

FIG. 2 shows the response of the thermistor 4 to temperature rise.

In the figure, A indicates the response when the current value of the thermistor 4 is set to a minute measurement current that causes almost no self-heating from the beginning.

B, C, and D show the responsiveness of the embodiment shown in FIG. 1, and were measured by changing the switching level of the N-gate thyristor 19.

If the current flowing through the thermistor 4 is switched in the middle of the measurement in this manner, the response can be made considerably faster.

In FIG. 2, T0 is the body temperature, but curve B shows that the switching level of the N-gate thyristor 19 is set at a temperature T3 that is slightly higher than the body temperature.

Even in this case, the response time can be considerably reduced compared to A.

Curve C shows that the switching level of the N-gate thyristor 19 is delayed so that the contact switches when the temperature of the thermistor 4 reaches a temperature slightly higher than body temperature.

In this case, the response will be even faster.

If the switching is further delayed, the response will actually worsen.

Curve D shows this. Experimentally, the response time is shortest when the contact is switched at a temperature 2 to 3 degrees Celsius higher than body temperature (38 to 39 degrees Celsius).

In this experiment, the ratio between the initial current value and the current value flowing through the thermistor 4 after the relay contact was switched was 10:1.

As described above, the thermometer of the present invention includes a power source, a latching relay that is connected to the power source via a capacitor and switches the switching contact to one side using the capacitor charging current when the power is turned on, and the latching relay. A closed circuit is constituted by the thermistor, which rapidly heats itself by supplying a relatively large current from the power source through the first resistor in response to switching of one side of the switching contact, and the capacitor and the latching relay. a switch element that detects an increase in the temperature of the thermistor to near the temperature of the temperature-measuring object and conducts it to cause a capacitor discharge current to flow through the latching relay to switch the switching contact to the other side; A second circuit that constitutes a temperature measuring bridge circuit with the thermistor in response to switching to the other side.
, the third and fourth resistors, the required temperature measurement time can be shortened and the operation for temperature measurement 9 is simple.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the thermometer of the present invention, and FIG. 2 is a response characteristic diagram for explaining its operation. 4...Temperature thermistor, 9,10.11...
...Relay contact, 19...N gate sirisk, 22...Relay, 23...Capacitor.

Claims (1)

[Claims] 1. A power supply, a latching relay connected to this power supply via a capacitor and switching a switching contact to one side by the capacitor charging current when the power is turned on, and a latching relay that switches the switching contact to one side in response to the switching of the switching contact of this latching relay to one side. A thermistor, which rapidly self-heats when a relatively large current is supplied through the first resistor, and the capacitor and latching relay form a closed circuit, and the temperature of the thermistor is close to the temperature of the object to be measured. a switch element that detects a rise in temperature and conducts the capacitor discharge current to the latching relay to switch the switching contact to the other side; and the thermistor in response to the switching of the switching contact to the other side. A thermometer comprising second, third and fourth resistors forming a warming bridge circuit.