GB2058357A

GB2058357A - Averaging thermometer

Info

Publication number: GB2058357A
Application number: GB8025446A
Authority: GB
Original assignee: UK Secretary of State for Industry
Current assignee: UK Secretary of State for Industry
Priority date: 1979-09-04
Filing date: 1980-08-05
Publication date: 1981-04-08

Abstract

Improvements in or relating to temperature recorders. A problem with recordal of temperatures to produce an average for a given time period has been that the continuous temperature value has not been used. The invention converts the temperature to a current signal in a sensor (1) and then to a voltage (2). A voltage to frequency converter (3) produces a frequency pulse signal. An oscillator (5) signal is divided in a divider (6) to give a one day duration pulse which is divided (8) according to a selector (7). A second divider (9) divides the pulse signal by a related factor before counting in counter (10) and displaying the average temperature on a display (12) at the end of the time period. The invention finds use in energy conservation projects to monitor accurately the temperature average over several days. <IMAGE>

Description

SPECIFICATION Improvements in or relating to temperature recorders This invention relates to temperature recorders, in particular to averaging thermometers which record the temperature at a location over a period of time and provide an average temperature for that period.

In energy conservation projects it is often useful to measure the average temperature at a given location, especially in industrial installations. The information so obtained may be used to demonstrate whether a project is or is not saving energy over a given period of time. A technique which has been used to provide a measurement of average temperature is to record the temperature, at equispaced time intervals, on a recording device such as a chart recorder. The values recorded are subsequently averaged by hand. An automated procedure uses a data logger which records temperatures measured at discrete intervals of time and at the end of a predetermined period averages the values measured.

A problem with the above techniques is that only discrete values of temperature are recorded which may give rise to errors in a fluctuating temperature situation.

The present invention seeks to provide an averaging thermometer which records a temperature continuously over a time period and gives an average value of the temperature over the time period.

According to the present invention an averaging thermometer has: a temperature sensor which produces a temperature signal uniquely related in magnitude to the temperature at a desired location: a convertor which converts the temperature signal to a temperature pulse train of which one of the pulse frequency, pulse height or mark space ratio is a measure of the temperature; an integrator which provides a temperature integral from the temperature pulse train; a clock arranged to run for a specified time period over which integration takes place and a calculator which determines, from the temperature integral and the time period, the average temperature over the time period at the desired location.

The calculator may have a display on which the average temperature can be displayed visually.

Conveniently the instantaneous temperature can also be displayed on the display.

The pulse train frequency may be selected as a measure of the temperature at the desired location, and conveniently the calculator counts the pulses over the time period.

Advantageously the time period is determined by the duration of a timing pulse which is derived by dividing the clock output by an appropriate factor.

The temperature sensor, convertor, integrator, clock and calculator may be electrical devices.

Conveniently the clock is a crystal oscillator.

Advantageously the temperature signal is a current output from the temperature sensor.

Preferably the convertor comprises a first stage which gives a voltage output proportional to the current of the temperature signal, and a second stage which converts the voltage to a pulse train of proportional frequency. Most preferably the temperature sensor is a semiconductor temperature sensor.

The invention will now be described, by way of example only, with reference to the accompanying drawing which is a block schematic circuit diagram of a digital averaging thermometer.

A semiconductor temperature sensor 1, which is an AD 590KH, produces a direct current output which is linearly proportional to the absolute temperature sensed. The sensor 1 is connected to a front-end analogue circuit 2 by a two-core screened cable which has an approximate maximum length of 1 OOm. The front-end analogue circuit 2 which is an AD 537 KH converts the current output of the sensor 1 to a proportional voltage. The proportional voltage is then converted to a corresponding frequency by a voltage to frequency convertor 3. The frequency signal is passed through a pre-scaling divider 4 which is a 2'4 divider and converts the frequency range to a more convenient range.

A basic one day signal is derived from a crystal oscillator 5 which is of conventional construction and whose signal output is divided in a frequency divider 6 which is a three element binary divider chain CMOS 4020B dividing by 241 and thereby providing an output of one pulse per day.

The period of time over which the temperature sensor output is to be averaged is set on a time period selector 7 which causes programmable divider 8 to divide the output of frequency divider 6 by the number of days set on the time period selector, to give a single pulse for the desired time period. Simultaneously the time period selector 7 causes a scaling divider 9, which is two single digit CMOS dividers, to divide the output of pre'scaling divider 4 by a factor proportional to the number of days set on time period selector 7. The output of the scaling divider 9 is input to a four decade binary coded decimal counter 10 which is an ICM 727 IJI and also acts as a latch and display driver circuit. The counter 10 counts the pulses from the scaling divider 9 for as long as the pulse from programmable divider 8 is also input to it. A control unit 11 determines the commencement of averaging and at the completion of averaging, when the pulse from programmable divider 8 ends, causes transfer of the value stored in counter 10 via its latch to a display 12 which is a four digit common anode digital display. Operation of the control unit 11 also causes the time remaining in the time period to be displayed on display 12.

A battery power pack (not shown) comprising four 1 ISV cells will power the circuits for .approximately thirty days.

1. An averaging thermometer having: a temperature sensor which produces a temperature

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to temperature recorders This invention relates to temperature recorders, in particular to averaging thermometers which record the temperature at a location over a period of time and provide an average temperature for that period. In energy conservation projects it is often useful to measure the average temperature at a given location, especially in industrial installations. The information so obtained may be used to demonstrate whether a project is or is not saving energy over a given period of time. A technique which has been used to provide a measurement of average temperature is to record the temperature, at equispaced time intervals, on a recording device such as a chart recorder. The values recorded are subsequently averaged by hand. An automated procedure uses a data logger which records temperatures measured at discrete intervals of time and at the end of a predetermined period averages the values measured. A problem with the above techniques is that only discrete values of temperature are recorded which may give rise to errors in a fluctuating temperature situation. The present invention seeks to provide an averaging thermometer which records a temperature continuously over a time period and gives an average value of the temperature over the time period. According to the present invention an averaging thermometer has: a temperature sensor which produces a temperature signal uniquely related in magnitude to the temperature at a desired location: a convertor which converts the temperature signal to a temperature pulse train of which one of the pulse frequency, pulse height or mark space ratio is a measure of the temperature; an integrator which provides a temperature integral from the temperature pulse train; a clock arranged to run for a specified time period over which integration takes place and a calculator which determines, from the temperature integral and the time period, the average temperature over the time period at the desired location. The calculator may have a display on which the average temperature can be displayed visually. Conveniently the instantaneous temperature can also be displayed on the display. The pulse train frequency may be selected as a measure of the temperature at the desired location, and conveniently the calculator counts the pulses over the time period. Advantageously the time period is determined by the duration of a timing pulse which is derived by dividing the clock output by an appropriate factor. The temperature sensor, convertor, integrator, clock and calculator may be electrical devices. Conveniently the clock is a crystal oscillator. Advantageously the temperature signal is a current output from the temperature sensor. Preferably the convertor comprises a first stage which gives a voltage output proportional to the current of the temperature signal, and a second stage which converts the voltage to a pulse train of proportional frequency. Most preferably the temperature sensor is a semiconductor temperature sensor. The invention will now be described, by way of example only, with reference to the accompanying drawing which is a block schematic circuit diagram of a digital averaging thermometer. A semiconductor temperature sensor 1, which is an AD 590KH, produces a direct current output which is linearly proportional to the absolute temperature sensed. The sensor 1 is connected to a front-end analogue circuit 2 by a two-core screened cable which has an approximate maximum length of 1 OOm. The front-end analogue circuit 2 which is an AD 537 KH converts the current output of the sensor 1 to a proportional voltage. The proportional voltage is then converted to a corresponding frequency by a voltage to frequency convertor 3. The frequency signal is passed through a pre-scaling divider 4 which is a 2'4 divider and converts the frequency range to a more convenient range. A basic one day signal is derived from a crystal oscillator 5 which is of conventional construction and whose signal output is divided in a frequency divider 6 which is a three element binary divider chain CMOS 4020B dividing by 241 and thereby providing an output of one pulse per day. The period of time over which the temperature sensor output is to be averaged is set on a time period selector 7 which causes programmable divider 8 to divide the output of frequency divider 6 by the number of days set on the time period selector, to give a single pulse for the desired time period. Simultaneously the time period selector 7 causes a scaling divider 9, which is two single digit CMOS dividers, to divide the output of pre'scaling divider 4 by a factor proportional to the number of days set on time period selector 7. The output of the scaling divider 9 is input to a four decade binary coded decimal counter 10 which is an ICM 727 IJI and also acts as a latch and display driver circuit. The counter 10 counts the pulses from the scaling divider 9 for as long as the pulse from programmable divider 8 is also input to it.A control unit 11 determines the commencement of averaging and at the completion of averaging, when the pulse from programmable divider 8 ends, causes transfer of the value stored in counter 10 via its latch to a display 12 which is a four digit common anode digital display. Operation of the control unit 11 also causes the time remaining in the time period to be displayed on display 12. A battery power pack (not shown) comprising four 1 ISV cells will power the circuits for .approximately thirty days. CLAIMS

1. An averaging thermometer having: a temperature sensor which produces a temperature signal uniquely related in magnitude to the temperature at a desired location; a convertor which converts the temperature signal to a temperature pulse train of which one of the pulse frequency, pulse height or mark space ratio is a measure of the temperature; an integrator providing a temperature integral from the temperature pulse train; a clock arranged to run for a specified time period over which integration takes place and a calculator determining from the temperature integral and the time period the average temperature over the time period at the desired location.

2. An averaging thermometer as claimed in claim 1 in which the calculator has a display on which the average temperature can be displayed visually.

3. An averaging thermometer as claimed in claim 2 in which the instantaneous temperature can be displayed visually.

4. An averaging thermometer as claimed in any preceding claim in which the pulse train frequency is a measure of the temperature at the desired location.

5. An averaging thermometer as claimed in claim 4 in which the calculator counts the pulses over the time period.

6. An averaging thermometer as claimed in any preceding claim in which the time period is determined by the duration of a timing pulse which is derived by dividing the clock output by an appropriate factor.

7. An averaging thermometer as claimed in any preceding claim in which the temperature sensor, convertor, integrator, clock and calculator are electrical devices.

8. An averaging thermometer as claimed in claim 7 in which the clock is a crystal oscillator.

9. An averaging thermometer as claimed in claim 8 in which the temperature signal is a current output from the temperature sensor.

10. An averaging thermometer as claimed in claim 9 in which the convertor comprises a first stage giving a voltage output proportional to the current of the temperature signal, and a second stage converting the voltage to a pulse train of proportional frequency.

1 An averaging thermometer as claimed in claim 9 or 10 in which the temperature sensor is a semiconductor temperature sensor.

12. An averaging thermometer substantially as hereinbefore described with reference to the accompanying drawing.