JPH04502816A - Inductively coupled high temperature monitor - 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] Inductively coupled high temperature monitor Background of the invention 1. Field of invention The invention operates through nearly conductive objects that create unwanted reflected impedance. The present invention relates to an inductively coupled temperature monitor that can be used. More specifically, the invention provides of the soup can to monitor and remotely measure temperature information via an inductive link. Can operate within metal enclosures such as:

2. Explanation of conventional technology As is well known in the art, canned food is a hermetically sealed can or jar. It is often the best cooked of all. "Products stored in closed containers" U.S. Pat. No. 4,092,111 entitled ``Heat Treatment Apparatus for food sealed in cans or cups made of aluminum, plastic or glass It teaches equipment for processing products or pharmaceutical products.

The problem with these industrial processes is that the heat supplied by the oven is not uniform. That's what it means. Therefore, one or more closed cans or It is desirable to monitor the actual temperature inside the chamber. “To pack food into cans. U.S. Pat. No. 3,975,854 entitled ``Apparatus for teaches placing thermocouples in canned jars. This timer It is activated when the fluid in the chamber boils. However, this US patent Teach the use of thermocouples that must be connected to the timer circuit by Bare line production is not possible.

Therefore, to monitor the temperature and remotely measure and send that information to a remote control device. The traditional method of placing a small transmitter inside a cooking container (can, jar, etc.) There is a need that the art does not teach.

Summary of the invention The present invention is applicable to metal enclosures such as subcans, film processing cans, or industrial processes. Temperature-responsive transmissions capable of operating near or within the mixed metal enclosure used It is a trustworthy machine. In order to operate in these environments, small transmitters require (1) metal enclosures; Information signals can be transmitted through the shielding effect of objects; (2) metal enclosures; minimally affected by unwanted reflected impedance from

To meet the first objective, an inductive signal is generated to obtain temperature information from the metal enclosure. to be measured remotely. The unwanted shielding effect provided by the metal enclosure is frequency dependent The lower the frequency, the lower the unwanted shielding effect provided by the can.

The shielding action can prevent the emission of telemetry signals from the metal enclosure. Tradition If a portable field is used at the required low frequencies, it is not suitable for small transmitters. This would require an extremely long antenna. The inventor created a magnetic field at the appropriate frequency. Overcome this challenge using a non-propagating and inductive field that requires only a small coil did.

To meet the second objective, a unique circuit design provides Insulate the resonant circuit (containing the conducting coil). In traditional circuit design, conductive enclosures The reflective impedance generated by the oscillator affects the oscillator impedance. Therefore, the oscillation frequency changes accordingly. Temperature information is transmitted through changes in the oscillator frequency. The reflected impedance modifies the frequency and therefore the unknown Generates an error signal. To overcome this problem, the oscillator circuit uses a buffer amplifier connected to. Buffer amplifiers inject pulses of current into a resonant circuit to generate inductive signals. generate. The buffer amplifier is a reflected impedance coupled via a resonant circuit. Isolate the oscillator from This insulation allows nearby conductive objects, including metal enclosures, to Despite the unwanted reflected impedance caused by It can be measured at intervals.

Invented temperature monitors generally measure temperature to produce a temperature-dependent output frequency. a sensing crystal and an oscillator to produce an output at a frequency determined by the temperature sensing crystal. An oscillator, a resonant circuit including a coil inductor that emits a magnetic signal, and an oscillator. coupled to buffer the oscillator from reflective loading from nearby conductive objects and a buffered output amplifier that injects a current pulse into the coil inductor. is an inductive output signal with a frequency that depends on the temperature sensed by the temperature-sensing crystal. occurs.

The first novel feature of this device is that it links the temperature within a metal enclosure such as a subcan. It is an ability that can be measured continuously.

A second novel feature of the invention is a buffer amplifier coupled to a temperature sensitive crystal oscillator. using the reflective impedance provided by a nearby conductive object to connect the oscillator to It should be insulated from

A third novel feature is the induction The key is to select the operating frequency of the link.

The fourth novel feature sends a signal through the metal enclosure to transmit temperature information. It is the use of an inductive field.

A fifth novel feature reduces bonding with the metal enclosure and A large inductive signal is radiated by placing a conductor coil. It is.

Brief description of the drawing FIG. 1 shows the present invention for telemetering temperature information through a metal enclosure to a remote receiver. It is a figure for detailed explanation.

FIG. 2 shows the present invention in which a two-stage buffer amplifier isolates the temperature-sensing oscillator from the resonant circuit. It is a schematic diagram.

Description of the preferred embodiment FIG. 1 shows one of the environments for which the present invention is intended. The small temperature sensor 10 is It is placed inside a metal enclosure, such as a can, and measures the internal temperature. induction coil 14 generates an inductive field that is coupled to and detected by a remote receiver 16. inductive field The frequency is varied as a function of the sensed temperature and provides information about the internal temperature of the subcan. It can be remotely measured by the information.

The metal enclosure 12 provides a difficult environment for telemetry of information. The metal surface Acts as a shield, quickly blocking transmitted radio signals. Soup can is induced A short section of the secondary coil that can couple with the coil 14 and absorb most of its magnetic field. Acts as a coiled wire. Unnecessary reflected impedance from conductive surfaces is removed by induction coils. 14 to change its impedance and change the oscillation frequency. In this way, far Inserts an error into the information included in the interval measurement signal. The present invention addresses each of these issues. independently overcome.

First, magnetically coupled non-propagating field telemetry is used. This allows you to send The machine can operate at lower frequencies and the subcan shielding effect is minimized. , there is no need for an extremely long antenna. In the preferred embodiment, the transmitter is 262°1 Operates at 44kHz (low enough frequency to minimize soup can shielding effects) do. With a propagating field, the antenna is too long for small transmitters to be practical. There will be. However, if it is a non-propagating field, it can penetrate the soup can and be detected remotely. Only a small coil 14 is needed to radiate a magnetic flux of sufficient strength to

Second, when using the transmitter in a shielded enclosure such as a soup can 12 , Applicants have recognized that the orientation of the coil is important. Inside a typical souvenir When in use, the axis of the coil 14 must pass through the side of the can as shown in Figure 1. Do not pass through the edges. With this arrangement, the magnetic flux is diverted through large shorted windings. (i.e. the cylindrical surface of the subcan acts as a short-circuited secondary winding) flow perpendicularly to the sides instead of This orientation allows for It has been found that the transmitted external field is improved by approximately 20 dB.

Third, this device eliminates unwanted reflections caused by nearby conductive surfaces during transmitter operation. Contains a unique circuit design that minimizes impedance effects. As already mentioned, reflection Impedances couple through a resonant circuit and change its oscillation frequency, thereby cause an error in the telemetry signal. Figure 2 is a schematic diagram of this device, with temperature sensing A buffer amplifier 18 is provided between the crystal oscillator 20 and the resonant circuit 22 including the induction coil. Indicates use. Buffer amplifiers provide the necessary isolation and reduce reflected impedance. If the device operates near (or inside) conductive objects that may cause make it possible to

Oscillator 20 is a variation of the Pierce oscillator, using an inverting amplifier to induce crystal 26. operate in the guided area. The oscillation frequency is set by crystal 26. Crystal 26 is 5 tatex TS-2 tuning fork that produces an output frequency that changes with temperature . Therefore, the oscillator produces a substantially square wave output on pin 11, and its oscillation frequency The number changes with sensed temperature.

The oscillator output (pin 11) is connected to the input of buffer amplifier 18 via capacitor 32. be combined. This class C buffer amplifier uses two transistors to handle high input Obtaining impedance. The first transistor 28 isolates the next amplifier Together they form a common collector stage without mirror feedback. second transition Star 30 is a common emitter stage that provides amplification. Output from buffer amplifier (pin 1) is input to the resonant circuit 24 and injects a current pulse into the resonant circuit. Combined con When capacitor 32 is charged to +3.2 volts, pin 12 transistor conducts. , at which point the output transistor is turned off again, so the timing is well maintained. It will be done. A current of 30 mA from pin l circulates through tuned circuit 22 at approximately 200 mA-rms. Maintain ring current. This circulating current flows through the coil 2 necessary to remotely measure temperature information. Establish the desired local induction field at 4.

The inductor coil 24 is constructed using 5 layers of 8-inch wire using No. 18 copper wire to maintain a high Q. It is formed in Mandel. Each coil has 12 turns Wound in two layers of wire. The inductance of the coil is approximately 8 Hy. Inductor・ Coil 24 emits a magnetic field whose frequency is directly related to the sensed temperature. . As mentioned above, the insulation between the resonant circuit and the oscillator reduces the magnetic flux. The frequency actually indicates the sensed temperature.

In operation, this device works in an enclosed metal enclosure such as a Subcan. It is sealed inside the body and remotely measures temperature information. This device is like a soup can Although described as operating within a solid metal enclosure, this device an area wholly or partially surrounded by a conductive surface that creates an radial impedance It is equally applicable to a variety of industrial applications that measure temperature.

Many modifications and variations of the present invention are possible in light of the above teachings. Therefore Therefore, it is possible to carry out the invention within the scope of the claims in ways other than those specifically described. should be understood.

FIG. 1 international search report

Claims (6)

[Claims] 1. For sensing physical parameters and for telemetry of inductive signals equipment that operates near conductive objects that create unwanted reflected impedance. In the device that for producing an output signal dependent on the magnitude of said sensed physical parameter; and a sensor of an output coupled to the sensor and at a frequency determined by the output signal of the sensor; oscillator means for generating; a resonant circuit including a coil inductor, and between said oscillator means and said resonant circuit; coupled buffered output amplifier means, before being caused by a nearby conductive object; for buffering said oscillator means from reflected loads affecting said resonant circuit; and , buffer output amplifier means for injecting current pulses into said resonant circuit; , wherein the coil inductor of the resonant circuit is connected to the sensed physical conductor. It is characterized by generating an inductive output signal with a frequency that depends on the magnitude of the parameter A device that does this. 2. The sensor is a temperature sensitive crystal for producing a temperature dependent output frequency. 2. The device according to claim 1. 3. The resonant circuit has a substantially identical 3. The device of claim 2, wherein the device is frequency tuned. 4. The buffer output amplifier includes a first transistor common collector stage for isolation. and a second transistor common emitter stage for amplification. 5. When the device operates in a metal subtype can, the coil inductor is arranged with its axis passing through the side of the can, and the induced magnetic flux couples to the soup-shaped can. 3. The apparatus of claim 2, wherein the apparatus reduces . 6. The operating frequency band is selected to minimize the shielding effect of nearby conductive objects. 3. Apparatus according to claim 2.