Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
  • G01K7/20—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit
  • G01K7/206—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit in a potentiometer circuit
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
  • G01K7/20—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit
  • G01K7/21—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit for modifying the output characteristic, e.g. linearising
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
  • G01K7/24—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit
  • G01K7/25—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit for modifying the output characteristic, e.g. linearising

Definitions

• the present invention relates to analog-to-digital (A/D) conversion and, in particular, to an apparatus for switching the resolution of an analog-to-digital converter input to provide for improved sensitivity.
• FIGURE 1 wherein there is shown a circuit diagram of a conventional analog-to- digital (A/D) converter based variable sensor 10 as is known in the prior art .
• a voltage supply 12 is included having a positive terminal 14 and a negative (ground) terminal 16.
• a voltage divider circuit 18 comprised of two series connected resistors 20.
• a first one of the resistors 20(1) is connected between the positive terminal 14 and a node 22.
• a second one of the resistors 20(2) is connected between the node 22 and the negative terminal 16.
• the node 22 is connected through a lead 24 to the input of an analog-to-digital converter 26.
• the variable being sensed by the sensor 10 is the voltage output from the voltage supply 12.
• the voltage supply 12 may accordingly comprise a battery.
• the variable being sensed by the sensor 10 is temperature.
• the second resistor 20(2) accordingly comprises a temperature sensitive thermistor.
• an analog signal having a voltage related (i.e., proportional) to the measured variable (voltage or temperature) is generated by the voltage divider circuit 18 at node 22 and applied via lead 24 to the input of an analog-to-digital converter 26.
• the voltage of the analog signal on lead 24 is then converted to a digital signal value for output from or for further processing by the analog-to-digital converter 26.
• the analog-to-digital converter 26 may comprise a discrete circuit element (as shown) or alternatively may comprise a part of a multi- function circuit element 28 (such as a micro-controller) .
• a discrete circuit element as shown
• a multi- function circuit element 28 such as a micro-controller
• a battery voltage sensor where a user may need to know not only whether the battery level is high or low, but also how quickly the voltage is decreasing.
• it .is often necessary for the sensed data concerning the variable to be evaluated with differing degrees of resolution.
• Adjustment in resolution of an analog signal output from a voltage divider circuit is provided in a first embodiment by selectively connecting and disconnecting a resolution resistance in parallel with one of the resistances comprising the voltage divider circuit.
• the analog signal output from the voltage divider circuit is applied to a scale changing amplification circuit, and the adjustment is provided by selectively connecting and disconnecting a resolution resistance in parallel with a feedback resistance of the amplification circuit to make an adjustment in gain (amplification) of the analog signal.
• a transistor switch operating in response to an applied control signal effectuates the selective parallel connection and disconnection of the resolution resistance to provide switchable (high vs. low) resolution for the sensed variable.
• FIGURE 1 (previously partially described) is a circuit diagram of a conventional prior art analog-to- digital (A/D) converter based variable sensor;
• FIGURE 2 is a circuit diagram for a first embodiment of an analog-to-digital (A/D) converter based variable sensor with resolution adjustment in accordance with the present invention.
• A/D analog-to-digital
• FIGURE 3 is a circuit diagram for a second embodiment of an analog-to-digital (A/D) converter based variable sensor with resolution adjustment in accordance with the present invention.
• A/D analog-to-digital
• N 7 —- 1 — N (1)
• Rj_ is the resistance of the first resistor
• R 2 is the resistance of the second resistor 20 (2) . Equation (1) illustrates that the larger the value of R 2 in comparison to the value of R ⁇ , the more sensitive
• V is to changes in V and, hence, the greater the resulting resolution provided by V .
• R a is equal to three ohms (3 ⁇ ) and that R 2 is equal to five ohms (5 ⁇ ) .
• Equation (1) for a V equal to ten volts (10V) , V is equal to 6.25V. If V were to now change to twelve volts (12v) , V would equal 7.5V. This is a change of 1.25V in V for a two volt swing in V. Now decrease the value of R x to two ohms (2 ⁇ ) . For a V still equal to ten volts (10V) , V is now equal to 7.14V. If
• Equation (1) further illustrates that, for a fixed
• V is to changes in R 2 and, hence, the greater the resulting resolution provided by V .
• R x is equal to three ohms (3 ⁇ ) and that V is equal to ten volts (10V) .
• V is equal to 5.71V.
• R 2 is equal to four ohms (4 ⁇ )
• V is equal to 6.67V. This is a change of 0.96V in V for a two ohm swing in R 2 .
• FIGURE 2 wherein there is shown a circuit diagram for a first embodiment of an analog-to-digital (A/D) converter based variable sensor 100 in accordance with the present invention.
• a voltage supply 112 is included having a positive terminal 114 and a negative (ground) terminal 116.
• a voltage divider circuit 118 comprised of a plurality (two shown) of series connected resistors 120.
• a first one of the resistors 120(1) is connected between the positive terminal 114 and a node 122.
• a second one of the resistors 120(2) is connected between the node 122 and the negative terminal 116.
• the node 122 is connected through a lead 124 to the input of an analog-to-digital converter 126 comprising a part of a multi-function circuit element 128 (such as a microcontroller) .
• the sensor 110 further includes a semiconductor transistor switch 130 comprising either a field effect transistor (FET) device (as illustrated) or a bi-polar transistor device (not shown) .
• the switch 130 includes a drain terminal 132 connected to the positive terminal 114, a gate terminal 134 connected to an output port 136 of the micro-controller 128, and a source terminal 138.
• the sensor 110 further includes a resolution resistor 140 connected between the source terminal 138 and the node 122 which is connected through the lead 124 to the input of the analog-to-digital converter 126.
• a signal selectively output by the micro-controller 128 from port 136 controls the operation of the switch 130 ("off" vs.
• R ⁇ is the resistance of the first resistor 120(1) ;
• R r is the resistance of the resolution resistor 140; and R eff is the resistance of the effective resistor
• the variable being sensed by the sensor 110 is change in the voltage output from the voltage supply 112.
• the voltage supply 112 may accordingly comprise a battery.
• the sensor 110 operates in two resolution modes. In a low resolution mode (i.e., a mode where the sensor 110 is less sensitive to changes in the voltage output from the voltage supply
• the micro-controller 128 operates to output a signal from port 136 controlling the operation of the switch 130
• the micro-controller 128 operates to output a signal from port 136 controlling the operation of the switch 130 ("on") in effectively connecting the resolution resistor 140 to the positive terminal 114 and thus forming the effective resistor 120(1) '.
• the value of the effective resistor 120(1) ' is less than the value of the first resistor 120 (1) .
• an analogous operation of the sensor 110 may be obtained by using the switch 130 to selectively connect and disconnect the resolution resistor 140 in parallel with the second resistor 120(2) between the node 122 and the negative terminal 116.
• low resolution mode occurs when the switch 130 is turned “on” by the micro-controller 128, and high resolution mode occurs when the switch 130 is turned “off” by the micro-controller.
• the variable being sensed by the sensor 110 is temperature.
• the second resistor 120(2) in this implementation comprises a temperature sensitive thermistor.
• the sensor 110 again operates in two resolution modes. In a low resolution mode (i.e., a mode where the sensor 110 is less sensitive to changes in the resistance of the thermistor) , the micro-controller 128 operates to output a signal from port 136 controlling the operation of the switch 130 ("on") in effectively connecting the resolution resistor 140 to the positive terminal 114 and thus forming the effective resistor 120(1) ' .
• the micro-controller 128 operates to output a signal from port 136 controlling the operation of the switch 130 ("off") in effectively disconnecting the resolution resistor 140 from the positive terminal 114.
• the value of the effective resistor 120(1) ' is less that the value of the first resistor 120 (1) .
• FIGURE 3 wherein there is shown a circuit diagram for a second embodiment of an analog-to-digital (A/D) converter based variable sensor 210 in accordance with the present invention.
• a voltage supply 212 is included having a positive terminal 214 and a negative (ground) terminal 216.
• a voltage divider circuit 218 comprised of a plurality (two shown) of series connected resistors 220.
• a first one of the resistors 220(1) is connected between the positive terminal 214 and a node 222.
• a second one of the resistors 220(2) is connected between the node 222 and the negative terminal 216.
• the node 222 is connected through a lead 224 to a first input 250 of an operational amplifier 252.
• a second input 254 of the operational amplifier 252 is connected to the negative (ground) terminal 216.
• An output 256 of the operational amplifier 252 is connected to the first input 250 through a feedback resistor 258. This effectively configures the operational amplifier to operate as a scale changer with respect to the received analog signal generated at the node 222.
• the output 256 of the operational amplifier 252 is further connected to the input of an analog-to-digital converter 226 comprising a part of a multi-function circuit element 228 (such as a micro-controller) .
• the sensor 210 further includes a semiconductor transistor switch 230 comprising either a field effect transistor (FET) device (as illustrated) or a bi-polar transistor device (not shown) .
• the switch 230 includes a drain terminal 232 connected to the output 256 of the operational amplifier 252, a gate terminal 234 connected to an output port 236 of the micro-controller 228, and a source terminal 238.
• the sensor 210 further includes a resolution resistor 140 connected between the source terminal 238 and the first input 250 of the operational amplifier 252 which is connected to node 222.
• a signal selectively output by the micro-controller 228 from port 236 controls the operation of the switch 230 ("off" vs.
• R f is the resistance of the feedback resistor 258
• R r is the resistance of the resolution resistor 240
• R eff is the resistance of the effective feedback resistor 258 ' .
• the variable being sensed by the sensor 210 is change in the voltage output from the voltage supply 212.
• the voltage supply 212 may accordingly comprise a battery.
• the sensor 210 operates in two resolution modes. In a high resolution mode (i.e., a mode where the sensor 210 is more sensitive to changes in the voltage output from the voltage supply 212) , the micro-controller 228 operates to output a signal from port 236 controlling the operation of the switch 230 ("off") in effectively disconnecting the resolution resistor 240 from the output 256 of the operational amplifier 252. In accordance with Equation (3), the value of the feedback resistor 258 is more than the value of the effective feedback resistor 258'.
• the micro-controller 228 operates to output a signal from port 236 controlling the operation of the switch 230 ("on") in effectively connecting the resolution resistor 240 in parallel with the feedback resistor 258 and thus forming the effective feedback resistor 258'.
• the value of the effective feedback resistor 258 ' is less than the value of the feedback resistor 258.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Analogue/Digital Conversion (AREA)
• Control Of Amplification And Gain Control (AREA)
• Electrophonic Musical Instruments (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=25213758

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (12)

Family Cites Families (4)

• 1998
  • 1998-03-04 JP JP53871898A patent/JP2001516529A/ja not_active Ceased
  • 1998-03-04 KR KR1019997007956A patent/KR20000075877A/ko not_active Application Discontinuation
  • 1998-03-04 AU AU66818/98A patent/AU6681898A/en not_active Abandoned
  • 1998-03-04 WO PCT/US1998/004167 patent/WO1998039624A1/en not_active Application Discontinuation
  • 1998-03-04 CN CN98803118A patent/CN1249811A/zh active Pending
  • 1998-03-04 EP EP98908900A patent/EP0965031A1/de not_active Withdrawn
  • 1998-03-04 BR BR9807989-1A patent/BR9807989A/pt not_active IP Right Cessation
  • 1998-03-04 EE EEP199900381A patent/EE9900381A/xx unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events