Patent GB-1510308-A (GB)
Title: Determining the average temperature of a flow of gas
IPC: G01K3/02
Filed: 1974-08-14
Abstract: 1510308 Measuring average temperature of flowing gas BRITISH GAS CORP 1 Aug 1975 [14 Aug 1974] 35785/74 Heading G1N The invention relates to a device for use with a gas flowmeter for automatically averaging the temperature of the gas flow with respect to its volume. The device comprises a temperature sensing device, e.g. a platinum resistance thermometer T1, for sensing the temperature of the gas flow through the flowmeter and means, e.g. a voltage to frequency converter, for deriving an output signal representing the "instant" temperature recorded by the device. A first summing means e.g. an UP-counter U/C1 has an input which in use, is coupled to the flowmeter such that successive flow signals from the flowmeter each representing the flow of a predetermined volume of gas are totalled in the first summing means and a second summing means e.g. an UP-DOWN counter UD/C3 and a temporary store C5 is fed with the derived output signal from the temperature sensing device whenever a flow signal is entered into the first summing means U/C1 and totals successive temperature signals. Means are provided for automatically dividing the total stored in the second summing means by the total stored in the first summing means whenever the totals are updated. The output of the dividing means thus represents the average temperature this being indicated by a means responsive to the last mentioned output. The dividing means comprises a further counter C4 which is parallel loaded with the UP counter U/C1 and means is provided for counting down the further counter C4 and the UPDOWN counter UD/C3 at 500 kHz. Since the count in counter UD/C3 is always larger than that in counter U/C1 at any time the further counter C4 will read zero before counter UD/C3. At this time the further counter C4 is re-loaded with a count equal to that which was immediately previously in the counter U/C1 and the count down is continued with further re-loading, if necessary, until the count in counter UD/C3 reaches zero. At each zeroing of the further counter C4 a pulse is fed to an UP-DOWN counter UD/C6 and the number of pulses emitted until the count in counter UD/C3 reaches zero represents the average temperature. While the division is proceeding, that is while the count in counter UD/C3 is being reduced, the original count of the counter UD/C3 is stored in the temporary store C5 such that the original count can be restored to the counter UD/C3 after the dividing operation. A further UP-DOWN counter UD/C2 is provided for storing the "instant" temperature. The average temperature or the "instant" temperature may be displayed on DD1 selectively by depression of a button S1 or S2 respectively. Since the device is limited to approximately 100 operations per hour a pre-set divider Dl is provided to cater for signals from the flowmeter which exceed 100 per hour. Negative temperatures are allowed for in the display by the provision of flip-flops FF1, FF2, associated with the counters UD/C6 and UD/C2 respectively. The device is controlled by a control logic which resets the device on actuation of a switch 53.