GB2042733A

GB2042733A - Energy Measuring Apparatus

Info

Publication number: GB2042733A
Application number: GB7841942A
Authority: GB
Original assignee: HPE SUPPLIES Ltd
Current assignee: HPE SUPPLIES Ltd
Priority date: 1978-10-25
Filing date: 1978-10-25
Publication date: 1980-09-24

Abstract

Energy measuring apparatus for measurement of heat units used in a water or central heating system, to provide a display of the amount of heat used in the system or parts thereof, comprises temperature sensors 3 and 4 located in the flow and return pipes 1, 2 of the system and a transducer 7 to sense the flow rate through the system. Signals from the sensors and transducer are fed to square wave oscillators 5, 6 and 8 respectively the frequency of which increases with increased temperature or flow. A further fixed frequency oscillator 9 increments a continuous counter 10 to provide a time constant for an electronic circuit including a plurality of gates 15, 16, 18-22, an up/down counter 17 and a motor 24 which drives a display 27 showing heat units consumed. <IMAGE>

Description

SPECIFICATION Energy Measuring Apparatus This invention relates to energy measuring apparatus.

More specifically the invention provides for apparatus for measuring energy losses in a fluid system and in particular but not exclusively the heat energy used or supplied in a heating system such as a central heating or water heating system.

The energy measuring apparatus according to the invention may be usefully employed to monitor the fluid flow rate and to measure the flow and return temperatures in a central heating system to produce a signal proportional to the heat units being used or supplied between the input and output of the heating system and to drive a mechanical numerical display device or an electrical digital display to show the amount of heat used or supplied to the system in appropriate units.

According to the invention energy measuring apparatus comprises a first and second length of pipe through which the flow and return fluid in a heat energy absorbing fluid system can be made to flow, means for providing a fluid flow frequency signal relative to the rate of fluid flow through one of said pipe lengths, two temperature sensors, one in each of said pipe lengths and each providing a variable signal dependent on the temperature of the fluid in their respective pipe length, a first square wave oscillator connected to one of said temperature sensors and a second identical oscillator connected to the other sensor, a third square wave oscillator having a predetermined fixed frequency and arranged to actuate a continuous time counter, outputs from said time counter at predetermined intervals arranged to actuate gates to an up/down counter in an electronic circuit, the output of the first and second oscillator and the fluid flow signal being fed to the up/down counter through said gates to increment the up/down counter, the arrangement being such that the frequency of the first and second oscillators and the fluid flow signal increases with increases in temperature and flow rate of the fluid in the pipe lengths and the time taken by the flow signal to empty the up/down counter of the difference between the output frequencies of the first and second oscillators is directly proportional to the difference between the flow and return temperatures and the flow rate of the fluid in the pipe lengths, said time being provided by said electronic circuit to hold the output of a gate high and to actuate indicating means to display heat units consumed.

The means for providing a fluid flow frequency signal may comprise an oscillator whose frequency is arranged to be proportional to the fluid flow rate in one of the pipe lengths.

The means for providing a fluid flow frequency signal may comprise a transducer located in one of the pipe lengths to provide a signal dependent on the fluid flow rate through the pipe length, the signal being fed to an oscillator to vary the frequency of the oscillator proportional to changes in fluid flow rate through the pipe lengths.

The transducer may be in the form of a strain gauge.

Preferred embodiments of the invention are illustrated by way of example in the accompanying drawings in which: Fig. 1 is a schematic diagram of energy measuring apparatus according to the invention, Referring to the drawing, a first pipe length 1 and a second pipe- length 2 are arranged to that the flow and return fluid of a heat energy absorbing fluid system which has to be measured can be made to flow therethrough. The pipe lengths may be constituted by sections of the flow and return pipes of the fluid circuit which has to be measured or they may be incorporated in the apparatus and connectable to the flow and return pipes in the fluid system to be measured.

Temperature sensors 3 and 4 are fixed in thermal relation to the pipe lengths 1 and 2 to sense the temperatures of the flow and return fluid in the pipe lengths. The sensors may comprise silicone diodes, thermistors or the like thermal sensing devices which provide a signal dependent on the temperature of the fluid in the pipe lengths.

The signals from the sensors 3 and 4 are fed to a first oscillator 5 and a second oscillator 6 respectively.

The oscillators each have a square wave output arranged to vary linearly dependent on the temperature of the sensors.

A transducer 7 which senses the fluid flow rate or variations in the fluid flow rate in one of the pipe lengths produces a signal which is fed to a third square wave oscillator 8, the output of which provides a fluid flow frequency signal which varies with the fluid flow rate in the pipe length.

A further fixed frequency oscillator 9 is arranged to oscillate at a predetermined frequency to increment a continous counter 10 which provides a time constant for an electronic circuit including a plurality of gates and an up/down counter.

The outputs from the oscillators 5, 6 and 8 are also fed through the gates to the up/down counter in the electronic circuit.

For the purpose of clarity we refer to the oscillator 9 as having a fixed frequency of 1 Hz and the continuous counter 10 being a divide by one hundred counter which is incremented once every second by the output of the oscillator 9. The counter 10 therefore continuously counts from 00 to 99 and several outputs are taken from the counter at predetermined intervals. It will of course be understood that the frequency of the oscillator 9 and the increments of the counter can be arranged to provide any suitable time constant.

At count 02 of the continuous counter 10 an output 11 is at logic one for one second, at count 04 an output 12 is at logic one for one second, between count 00 and 09 an output 13 is at logic one for ten seconds and at count 00 an output 1 4 is at logic one for one second.

The output 13 is taken to gates 1 5 and 1 6 and during the time when output 13 is at logic one at count 02 the output 11 opens a gate 1 5 to set an up/down counter 17 to a count-up mode and at the same time a gate 18 is open to allow the output from the linear oscillator 5 to pass via a gate 1 9 into the up/down counter 1 7 where the output frequency of oscillator 5 is stored during this second. Two seconds later at count 04 of the continuous counter the output at 1 2 opens a gate 1 6 for one second allowing the output frequency of oscillator 6 to be subtracted from the up/down counter 1 7 so that the difference between the two output frequencies of oscillators 5 and 6 is stored in the up/down counter.This difference represents the heat loss between the flow and return fluids being monitored. Output 1 3 is taken via an inverter I to a gate 20 and the output from oscillator 8 is also taken to gate 20. The inverted output is also taken to a gate 21. Gates 20 and 21 are held closed by the inverted output from 1 3 during counts 00-09. When the up/down counter 1 7 has any number other than 00 stored in its registers gate 23 is held open. At count 10 gate 20 is opened to allow the output frequencyof oscillator 8 to be fed through gate 1 9 to the up/down counter to increment the counter 1 7 down from the stored difference frequency.At the same time the output from gate 23 is taken to gate 21 to hold it open and to drive a motor 24 via a transistor 25 and triac 26. When the frequency of oscillator 8 has cleared the up/down counter, a signal is fed to gate 23 which cioses gates 20 and 21. At count 00 the output from 14 of continuous counter 10 is fed through gate 22 to reset the up/down counter ready to begin a new cycle. The motor 24 is of the synchronous fixed speed type and is used to increment a mechanical counter display 27 which displays heat units consumed.

Since the frequency of the oscillators 5 and 6 rise with increase in temperature of the sensors 3 and 4 respectively and the frequency of the flow rate oscillator 8 also increases with increased flow rate, it is arranged that these frequencies combine such that the time taken to empty the up/down counter of the difference frequency of oscillators 5 and 6 by the flow rate oscillator 8, is directly proportional to the difference between the flow temperatures and the flow rate.

The frequency range of oscillators 5, 6 and 8 can be varied to provide for various flow rate and temperature requirements of different fluid systems.

When there is a known constant flow rate in the fluid system to be monitored or a predetermined flow rate range is to be covered the transducer 7 may be omitted and the oscillator 8 is replaced by an oscillator whose frequency is selected to correspond to the flow rate or flow rate range required.

The transducer 7 may be in the form of a strain gauge located in one of the pipe lengths. The strain gauge being responsive to the fluid flow to vary the electrical resistance of the strain gauge which is connected to one leg of a Wheatstone bridge. The unbalanced output of the bridge circuit being fed to an amplifier whose output is fed to the oscillator 8.

The output from gate 21 could alternatively be used to gate an electronic counter driving an electronic display.

Claims

1. Energy measuring apparatus comprising a first and second length of pipe through which the flow and return fluid in a heat energy absorbing fluid system can be made to flow, means for providing a fluid flow frequency signal relative to the rate of fluid flow through one of said pipe lengths, two temperature sensors, one in each of said pipe lengths and each providing a variable signal dependent on the temperature of the fluid in their respective pipe length, a first square wave oscillator connected to one of said temperature sensors and a second identical oscillator connected to the other sensor, a third square wave oscillator having a predetermined fixed frequency and arranged to actuate a continuous time counter, outputs from said time counter at predetermined intervals arranged to actuate gates to an up/down counter in an electric circuit, the output of the first and second oscillator and the fluid flow signal being fed to the up/down counter through said gates to increment the upjdown counter, the arrangement being such that the frequency of the first and second oscillators and the fluid flow signal increases with increases in temperature and flow rate of the fluid in the pipe lengths and the time taken by the flow signal to empty the up/down counter of the difference between the output frequencies of the first and second oscillators is directly proportional to the difference between the flow and return temperatures and the ftow rate of the fluid through the pipe lengths, said time being provided by said electronic circuit to hold the output of a gate high and to actuate indicating means to display heat units consumed.

2. Energy measuring apparatus according to claim 1 in which the means for providing a fluid flow frequency signal comprises an oscillator whose frequency is arranged to be proportional to the fluid flow rate in one of the pipe lengths.

3. Energy measuring apparatus according to claim 1 in which the means for providing a fluid flow frequency signal comprises a transducer located in one of the pipe lengths to provide a signal dependent on the fluid flow rate through the pipe length, the signal being fed to an oscillator to vary the frequency of the oscillator proportional to changes in fluid flow rate through the pipe length.

4. Energy measuring apparatus according to claim 3 in which the transducer is in the form of a strain gauge.

5. Energy measuring apparatus substantially as hereinbefore described with reference to the accompanying drawings.