Digital thermometer modification for telemetry and analog recording

• US 4,218,916 A
• Filed: 02/09/1979
• Issued: 08/26/1980
• Est. Priority Date: 02/09/1979
• Status: Expired due to Term

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Mutziger, John S.
• Primary Examiner(s): Swisher, S. Clement
• Application Number:
  US06/011,059
• Time in Patent Office: 564 Days
• Field of Search: 73/1 F, 73/362 AR, 73/359, 73/360, 73/432 A
• US Class Current: 374/170
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: G01K 7/14 Arrangements for modifying the output characteristic, e.g. linearising

Abstract

Add-on circuitry for use with an electronic digital thermometer to provide a variable range analog output for applications such as telemetry and analog recording. An analog output circuit has offset and gain adjustments so that its output range can be adjusted to correspond to the desired range of temperatures to be measured without affecting the basic accuracy of the thermometer indicator readout. A circuit is connected to the thermometer input for adjustably simulating, in turn, a low and a high temperature reading corresponding to the limits of the expected temperature range to be measured. As the low temperature is simulated and read from the thermometer indicator, the offset is adjusted to provide the low level analog output. The high temperature is then simulated and the gain adjusted to yield the desired analog output, preferably near full scale. A relay circuit designed to have a low thermocouple effect is used to selectively couple the simulator circuit to the thermometer input without having to disconnect the thermocouple.

Claims

1. A system for measuring temperature including temperature responsive means for providing an electrical signal indicative of temperature, and circuit means coupled to the temperature responsive means for receiving the signal, the circuit means including indicator means responsive to the signal for providing an indication of temperature, the improvement comprising:

output means connected to the circuit means for providing a variable level output signal indicative of the temperature indication provided by the indicator means, the output means including means for adjusting the variable level output signal to provide an output signal variation from a first preselected level to a second preselected level as the indicator means varies between a first and a second temperature indication; and

signal simulating means connected to the circuit means for selectively providing an adjustable calibrating signal thereto and causing the indicator to indicate a temperature between the temperatures corresponding to the first and second temperature indications, inclusive, regardless of the temperature indicative signal for adjusting the variable level output signal means to provide the output signal corresponding to the calibrating signal.

2. The invention defined in claim 1 wherein the signal simulating means selectively provides the first temperature indication.

3. The invention defined in claim 2 wherein the signal simulating means selectively provides the second temperature indication.

4. A system for measuring temperature including transducer means for providing an electrical signal indicative of temperature, input circuit means for receiving the electrical signal, and signal conditioning means connected to the input circuit means and including readout means for providing an indication of the temperature, the improvement comprising:

adjustable circuit means coupled to the input circuit means for selectively providing an adjustable signal thereto simulating the electrical signal for a preselected temperature and causing the readout means to provide an indication of the preselected temperature;

output means connected to the signal conditioning means for providing an output signal which varies between a first level and a second level as the readout means correspondingly varies from a first to a second actual or simulated temperature indication, the output means including means for establishing a first desired level output indicative of the first temperature as the signal for the first temperature is simulated by the adjustable circuit means.

5. The invention defined in claim 4 wherein the output means further includes means for establishing a second desired level output as the signal for the second temperature is simulated.

6. A temperature measuring system including a thermocouple for providing an electrical signal indicative of temperature, an input circuit for receiving the electrical signal, and signal conditioning circuit means connected to the input circuit including an indicator for providing a reading indicative of the temperature, the improvement comprising:

analog output circuit means connected to the signal conditioning circuit means for providing an output signal having a level which varies with the indicator reading, the output circuit means including adjustable control means for selecting a desired output signal scale variation between a low and a high temperature reading; and

input simulator means connected to the input circuit for selectively providing a first and a second electrical signal and causing the indicator to read a first and a second temperature, the simulator means including means for adjusting the simulated electrical signals and causing the first temperature reading to correspond to a selected low temperature reading and the second temperature reading to correspond to a selected high temperature reading for adjusting the control means to provide the preselected scale variation while the first and second temperatures are simulated.

7. The invention defined in claim 6 wherein the input simulator means includes switch means operably connecting the means for adjusting and the input circuit for providing in turn the first and the second electrical signal to the input circuit.

8. The invention defined in claim 7 wherein the switch means comprises a relay having predetermined pull-in and hold-in voltages and current means connected to the relay for establishing at least the pull-in voltage and activating the relay, the switch means further comprising means for limiting the current flow through the relay for decreasing the voltage at the relay after activation of the relay to a level below the pull-in voltage but above or equal to the hold-in voltage of the relay to reduce heat build-up therein.

9. A temperature measuring system including thermocouple means for providing an electrical signal indicative of temperature, input circuit means for receiving the electrical signal, the input circuit means including offset means for providing an offset signal to compensate for temperature variations of the input circuit, and a conditioning circuit connected to the input circuit including indicator means for providing an indication of temperature, the improvement comprising:

output circuit means connected to the conditioning circuit for providing an output signal which varies with the temperature indication, the output circuit means including adjusting means for scaling the output signal to vary between a first and a second level as the temperature indication varies between a first and a second temperature indication;

signal means connected to the input circuit means for providing an adjustable calibrating signal thereto and causing the indicator to provide an indication of a temperature between the first and second temperature, inclusive, regardless of the temperature of the thermocouple means; and

means for disabling the offset means while the calibrating signal is provided to the input circuit.

10. The invention defined in claim 9 wherein the output circuit includes a gain and an offset control, and the signal means is adjusted to provide, in turn, a first and a second temperature indication whereby the offset control is adjusted while the first temperature is indicated and the gain control is adjusted while the second temperature is indicated.

11. A system for measuring temperature including a temperature responsive device for providing a signal indicative of temperature, and circuit means for receiving the signal and providing an indication of temperature, a circuit for providing an output signal which varies in level over a desired range as the temperature indication varies from a first to second value, comprising:

adjustable signal means connected to the circuit means for selectively providing a first and second signal to the circuit means to cause the temperature indication to indicate in turn the first and second values;

adjustable output means connected to the circuit means and including a variable offset control means for providing an output having a first level when the temperature indication indicates a preselected first temperature, the output means also including a variable gain control means for providing an output having a second level when the temperature indication indicates a preselected second temperature, so the output varies from the first to the second level as the temperature indication varies from the first to the second preselected temperature; and

wherein the signal means is adjustable for selecting the first and second values to correspond to the preselected first and second temperatures, respectively.