US 4,844,076 AGranted

Ingestible size continuously transmitting temperature monitoring pill

AssigneeThe Johns Hopkins University

InventorsJeffery C. Lesho, Arthur F. Hogrefe

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Abstract

A temperature responsive transmitter is disclosed. The transmitter utilizes a unique circuit design that allows encapsulation in an ingestible size capsule. The inventive circuit design uses a one transistor inverting amplifier with a tank circuit forming the link between the transistor's collector and the battery. The tank circuit is tuned to provide a lagging capacitive load which causes the inverting amplifier to oscillate. The tank circuit contains a coil inductor that emits a near field magnetic communications field containing temperature information. The ingestible size temperature pill can be configured in a rechargeable embodiment. In this embodiment the pill uses the inductive coil in the tank circuit as the magnetic pickup to charge a rechargeable nickel cadmium battery.

Claims17

Dependent claims

A miniaturized temperature responsive transmitter comprising:

a battery providing a voltage V.sub.b ;
reed-switch means adapted to be controlled by a magnet to disconnect the battery during storage;
a one-transistor inverting amplifier having an input and output and operably biased to said battery;
a temperature-sensitive crystal operably coupled between said input and output of said inverting amplifier and having a natural frequency dependent on local temperature;
a tank circuit having an inductor and a capacitor, operably coupled between said output of said inverting amplifier and said battery and tuned to a frequency lower than the natural frequency of said temperature-sensitive crystal for both providing a lagging phase shift at the output of said inverting amplifier and for emitting a near field magnetic signal from said inductor, wherein the frequency of said near field magnetic signal is dependent upon the frequency of the temperature sensitive crystal which is temperature dependent, and wherein said inverting amplifier acts as a switch causing said capacitor to charge and discharge through said inductor, thereby allowing the tank circuit to operate at 2 V.sub.b peak-to-peak volts.

2 more elements

A rechargeable, miniaturized temperature responsive transmitter comprising:

a rechargeable battery;
an inverting amplifier having an input and output and operably biased to said battery;
a temperature sensitive crystal operably coupled between said input and output of said inverting amplifier and having a natural frequency dependent on local temperature;
a tank circuit having a first and second terminal with an inductive coil connected therebetween, the first terminal of said tank circuit being connected to said inverting amplifier;
a current limiting device connecting said second terminal of said tank circuit to said battery, for limiting the current that can flow into said rechargeable battery;
a charging capacitor connected between said second terminal of said tank circuit and ground for storing electrical energy picked up by said inductor;
a diode connected between said first terminal of said tank circuit and said ground for rectifying full wave oscillation picked up on the inductor and for charging said charging capacitor;
and,
wherein said tank circuit is tuned to a frequency lower than the natural frequency of said temperature sensitive crystal, and wherein said tank circuit performs the following functions:
i. providing a lagging phase shift at the output of said inverting amplifier;
ii. emitting a near field magnetic signal from said inductor at a frequency dependent on the temperature sensitive crystal which is temperature dependent;
and,
iii. a power pickup used to recharge the rechargeable battery.

10 more elements

Dependencies are inferred from the claim text.