GB2202952A

GB2202952A - Pressure measuring apparatus

Info

Publication number: GB2202952A
Application number: GB08807546A
Authority: GB
Inventors: Michael Kennedy; John Kennedy
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-03-31
Filing date: 1988-03-30
Publication date: 1988-10-05
Anticipated expiration: 2008-03-30
Also published as: IE59833B1; IE870836L; GB8807546D0; GB2202952B

Abstract

The invention provides a gas pressure measuring and recording apparatus for use in combination with a pressure sensor 17. A voltage signal from the pressure sensor is converted to a frequency signal which is fed to a counter to provide a count value corresponding to a pressure measurement. If the instantaneous count value differs from a preceding value by more than a predetermined tolerance, the instantaneous count is stored in a RAM 20 with date and time. The pressure measurement and other associated data is indicated on a liquid crystal display 14 and recorded 15 by a hard copy printer, for use in gas leakage monitoring. <IMAGE>

Description

PRESSURE MEASURING APPARATUS The present invention relates to a pressure measuring apparatus and in particular to an apparatus for measuring and recording pressure in a gas supply.

Gas has been used for many years as a domestic energy source for heating and cooking purposes. With the discovery of natural gas, the use of gas as a source of energy has become even more widespread. Gas is of course a dangerous source of energy and can explode if certain pressure conditions are met, such as may occur if there is a leakage of the gas suply.

At present, gas leakage tests are usually carried out using a 'U' guage. The 'U' guage presently used has numerous disadvantages in particular the fact that the result analysis is determined by the operator who must determine whether or not a leak is present in a gas supply based on gas pressure measurements.

However, if an operator should check a gas supply and confirm it safe, and for some unknown reason a leak and possibly an explosion occurs at a later date, the operator has no way of actually proving that the gas supply was checked by him. This is a source of serious concern for the relevant people employed in the gas industry.

An object of the present invention is to mitigate the abovementioned disadvantages.

According to the invention there is provided a gas pressure measuring and recording apparatus for use in combination with a pressure sensor comprising, means for sensing a signal from the pressure sensor indicative of a gas pressure and means for displaying a pressure measurement.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a pressure measuring and recording apparatus according to the invention; Figure 2 is a schematic representation of the control circuitry; Figure 3 is a schematic block diagram of another embodiment of pressure measuring and recording apparatus according to the invention; and Figure 4 is a schematic block diagram of a pressure sensor circuit for use in the embodiment of Figure 3.

Referring now to Figures 1 and 2 wherein similar numerals have been used to indicate like parts, there is shown therein one embodiment of a pressure measuring and recording apparatus generally indicated at 10 according to the invention. The apparatus 10 comprises a housing 11 having a microprocessor 12 controlled by a number of input keys 13, an LCD display 14 and a printer 15 including a roll of paper 16 for providing a hard copy output. The apparatus 10 further includes a pressure transducer 17 adapted to be connected to a gas supply (not shown) by means of a conduit (not shown).

The pressure transducer 17 converts gas pressure into a voltage signal which if necessary is fed to an amplifier 18 and an analogue/digital converter 19. The output signal from the analogue/digital converter 19 is monitored by the microprocessor 12 to provide a numeric value for gas pressure and display this value on the LCD display 14 and also to provide a hard copy of the value on a roll of paper 16. The microprocessor 12 also has a memory 20 in which data relating to the operator name or code number, the job number, and the date etc., may be stored and which may also be printed on the paper roll. In addition, the microprocessor may have an inbuilt clock so that the time at which a particular measurement is taken may also be recorded.

The microprocessor 12 is preferably suitably programmed to carry out the pressure test over a predetermined period being two minutes. Some of the input keys 13 may be used for changing the variables in the programme. It will be appreciated that a suitable programme may be prepared by those having ordinary skill in the art.

In use, the pressure transducer is connected to a gas supply to be tested and once the programme is initialized the date, time and operator number are read and stored in a temporary memory (not shown) of the microprocessor 12. The programme then allows the pressure to be monitored for two minutes during which a number of readings are taken and the microprocessor will output the analysis of the readings on the LCD display and also on the paper roll, as a print out.

The print out thus generated can therefore be used as a signed record of installation integrity and may be used as part of an operator's responsibility report.

It will be appreciated that the apparatus 10 incorporates a feeder (not shown) for feeding the roll of paper 16. The microprocessor may also have programmed therein a number of prompts to readily inform the operator that certain information inputs are required.

Referring now to Figures 3 and 4 there is shown another embodiment of the invention. In Figures 3 and 4 a microcomputer control system 30 comprises a processor 31 linked via a communication bus to an EPROM 32, a system RAM 33, a first interface 34 and a seocnd interface 35. The second interface 35 has input/output connections 36, 37 and 38 to a keyboard 39, a visual display 40 and a sensor circuit 41 respectively. The control system 30 also includes a real time clock 42 and a logging RAM 43 as will be described below.

The sensor circuit 41 comprises a pressure transducer 44 connected via a gas supply part 45 to a supply of gas (not shown) the pressure of which is to be measured. The output signal from the pressure transducer 44 is connected to an amplifier 46 via lead 47 and the amplifier 46 is connected to a voltage to frequency converter 48 via lead 49. The output 50 from the voltage to frequency converter 48 is connected to lead 38 of the control system 30.

The pressure transducer 44 may be carried by a user and connected to a gas supply port 45 which is normally provided at a suitable location.

Alternatively, the pressure transducer 44 may be permanently connected to the gas supply port 45 (which may, for example, be buried in the ground). In this case, the end 51 of the lead 47 will be located at a suitable location so that a user can readily connect the lead 47 to the amplifier 46.

In use, the output signal from the transducer 44 on line 47 is amplified by amplifier 46 and is fed to voltage to frequency converter 48. The voltage to frequency converter 48 converts the voltage signal to a frequency which is outputted on line 50 and thus appears on line 38 to the interface 38. The interface 38 incorporates a counter (not shown) which registers a count which is representative of the frequency output of the voltage to frequency converter 48 and thus of the pressure measured by the transducer 44. The processor 31 interrogates the counter in the interface every one-tenth of a second (this process being activated by an interrupt signal from the real time clock 42) and measures this reading against the previous reading. If the current reading is different from the previous reading, by a predetermined amount or tolerance limit, the control system 30 stores this reading in the logging RAM 43. The tolerance limit is stored in the EPROM 32. The logging RAM 43 can store up to 999 records. The records stored in the logging RAM 43 may comprise information relating to the date, time and pressure reading. The count which is present in the counter of the interface 35 is readily converted to a pressure value by comparing the count with a look up table in the EPROM 32 having a range of count/ pressure values.

A separate record of the current pressure and time values is stored in the system RAM 33 for use in determining whether or not the next reading is within the set predetermined tolerance limits. The current values may also be provided on the display 40.

The interface 35 has a printer link 60 for outputting any required data to a printer (not shown) to provide a hard copy of test results. Also, a serial link 61 is provided to the interface 34 to enable information to be obtained from the system 30 over a communications network.

The apparatus may be operated from a mains power supply 62 or from a battery power supply 63. The power supply 63 is rechargable from the mains power 62 supply via a charging circuit 64. In addition, a back up battery power supply 65 is provided for the real time clock 42 and the logging RAM 43. The back up power supply 65 ensures that the information contained in the logging RAM 43 is secure in the event of a power failure and also ensures that the real time clock 42 continues to operate.

The keyboard 39 can be used to set various system parameters and to control the operation of the apparatus.

The control system 30, amplifier 46 and voltage to frequency converter 48 are preferably located in a portable housing also containing a printer and visual display 40.

The primary advantages of the invention are that it provides a simple apparatus for measuring and recording a gas pressure, and providing an immediate and accurate indication of pressure variations.

Claims

CLAIMS:

1. A gas pressure measuring and recording apparatus for use in combination with a pressure sensor comprising, means for sensing a signal from the pressure sensor indicative of a gas pressure and means for displaying a pressure measurement.

2. An apparatus as claimed in Claim 1 wherein the signal indicative of gas pressure is a frequency signal.

3. An apparatus as claimed in Claim 2 wherein the output signal of the pressure sensor is a voltage signal and is converted to a frequency signal.

4. An apparatus as claimed in Claim 3 wherein the voltage signal is amplified before being converted to a frequency signal.

5. An apparatus as claimed in any one of Claims 2 to 4 wherein the frequency signal is sensed by a counter.

6. An apparatus as claimed in Claim 5 wherein the counter is interrogated at predetermined regular intervals.

7. An apparatus as claimed in Claim 6 wherein the predetermined regular intervals are of the order of one-tenth of a second.

8. An apparatus as claimed in Claim 6 or 7 wherein the current counter value is compared with a previous counter value, and if the current counter value lies outside a tolelrance range associated with the previous counter value, the current counter value is stored.

9. An apparatus as claimed in Claim 8 wherein a record of date and time is stored with the current counter value.

10. An apparatus as claimed in any preceding Claim wherein the means for displaying a pressure measurement comprises a liquid crystal display.

11. An apparatus as claimed in any one of Claims 1 to 9 wherein the means for displaying a pressure measurement comprises a hard copy printer.

12. A gas pressure measuring and recording apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 or Figures 3 and 4.