Continuous electrochemical monitoring
A continuous electrochemical monitoring device according to an example includes an electrochemical transducer to continually generate a signal indicative of a characteristic of a user. The device includes a transimpedance amplifier to receive the signal from the transducer at a first input, receive a bias voltage at a second input, and generate an output voltage. The device includes an operational amplifier to receive the output voltage at a first input, and output an amplified output voltage. The device includes a differential analog to digital converter to receive the amplified output voltage at a first input, receive the bias voltage at a second input, and continually generate a digital output indicative of the characteristic of the user.
1 . A continuous electrochemical monitoring device, comprising:
an electrochemical transducer to continually generate a signal indicative of a characteristic of a user;
a transimpedance amplifier to receive the signal from the transducer at a first input, receive a bias voltage at a second input, and generate an output voltage;
an operational amplifier to receive the output voltage at a first input, and output an amplified output voltage;
a differential analog to digital converter to receive the amplified output voltage at a first input, receive the bias voltage at a second input, and continually generate a digital output indicative of the characteristic of the user;
a feedback resistor coupled between an output of the transimpedance amplifier and the first input of the transimpedance amplifier; and
a switch coupled in parallel with the feedback resistor between the output of the transimpedance amplifier and the first input of the transimpedance amplifier.
2 . The continuous electrochemical monitoring device of claim 1 , wherein the electrochemical transducer is a glucose transducer positioned on a body of the user, and wherein the characteristic is a glucose concentration of the user.
3 . The continuous electrochemical monitoring device of claim 2 , and further comprising:
a microcontroller unit to receive the digital output from the differential analog to digital converter and cause glucose concentration data to be wirelessly transmitted to a host device.
4 . The continuous electrochemical monitoring device of claim 1 , and further comprising:
a digital to analog converter to generate the bias voltage.
5 . The continuous electrochemical monitoring device of claim 4 , and further comprising:
a first resistor coupled between an output of the operational amplifier, and a second input of the operational amplifier.
6 . The continuous electrochemical monitoring device of claim 5 , and further comprising:
a second resistor coupled between the second input of the operational amplifier and a source of the bias voltage.
7 . The continuous electrochemical monitoring device of claim 6 , and further comprising:
a buffer having a first input coupled to an output of the digital to analog converter to receive the bias voltage, and an output coupled to the second input of the differential analog to digital converter.
8 . The continuous electrochemical monitoring device of claim 7 , wherein the output of the buffer is also coupled to a second input of the buffer and to the second resistor.
9 . The continuous electrochemical monitoring device of claim 1 , wherein the switch is controlled to open and close to compensate for an offset error of the transimpedance amplifier.
10 . The continuous electrochemical monitoring device of claim 9 , wherein a digital value output by the differential analog to digital converter while the switch is closed is subtracted from subsequent digital values output by the differential analog to digital converter while the switch is open.
11 . The continuous electrochemical monitoring device of claim 1 , wherein the electrochemical transducer generates currents in a range of 0-20 nA.
12 . The continuous electrochemical monitoring device of claim 9 , wherein the bias voltage is in a range of 150-600 mV.
13 . The continuous electrochemical monitoring device of claim 1 , wherein the switch is directly coupled between the output of the transimpedance amplifier and the first input of the transimpedance amplifier.
14 . A method, comprising:
continually measuring a characteristic of a user with an electrochemical transducer;
generating an output voltage with a transimpedance amplifier based on the measured characteristic and a received bias voltage;
amplifying the output voltage with an operational amplifier to generate an amplified output voltage;
continually generating digital output values with a differential analog to digital converter based on the amplified output voltage and the bias voltage;
providing a feedback resistor coupled between an output of the transimpedance amplifier and a first input of the transimpedance amplifier that receives the measured characteristic; and
providing a switch coupled in parallel with the feedback resistor between the output of the transimpedance amplifier and the first input of the transimpedance amplifier.
15 . The method of claim 14 , wherein the electrochemical transducer is a glucose transducer positioned on a body of the user, and wherein the characteristic is a glucose concentration of the user.
16 . The method of claim 15 , and further comprising:
receiving the digital output values with a microcontroller unit; and
wirelessly transmitting glucose concentration data based on the digital output values to a host device.
17 . The method of claim 14 , and further comprising:
controlling the switch to open and close to compensate for an offset error of the transimpedance amplifier.
18 . The method of claim 14 , wherein providing the switch comprises providing the switch directly coupled between the output of the transimpedance amplifier and the first input of the transimpedance amplifier.
19 . A continuous glucose monitoring device, comprising:
a glucose transducer to continually generate a signal indicative of a glucose concentration of a user;
a transimpedance amplifier to receive the signal from the transducer at a first input, receive a bias voltage at a second input, and generate an output voltage;
an operational amplifier to receive the output voltage at a first input, and output an amplified output voltage;
an analog to digital converter to receive the amplified output voltage at a first input, receive the bias voltage at a second input, and continually generate digital output values based on a difference between the amplified output voltage and the bias voltage; and
a microcontroller unit to receive the digital output values from the analog to digital converter and cause glucose concentration data to be wirelessly transmitted to a host device;
a feedback resistor coupled between an output of the transimpedance amplifier and the first input of the transimpedance amplifier; and
a switch coupled in parallel with the feedback resistor between the output of the transimpedance amplifier and the first input of the transimpedance amplifier.
20 . The continuous glucose monitoring system of claim 19 , wherein the glucose transducer generates currents in a range of 0-20 nA, and wherein the bias voltage is in a range of 150-600 mV.