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WO1993007601A1 - Systeme d'etalonnage pour instruments de mesure - Google Patents

Systeme d'etalonnage pour instruments de mesure Download PDF

Info

Publication number
WO1993007601A1
WO1993007601A1 PCT/CA1992/000436 CA9200436W WO9307601A1 WO 1993007601 A1 WO1993007601 A1 WO 1993007601A1 CA 9200436 W CA9200436 W CA 9200436W WO 9307601 A1 WO9307601 A1 WO 9307601A1
Authority
WO
WIPO (PCT)
Prior art keywords
value
displayed
parameter
display
actuator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CA1992/000436
Other languages
English (en)
Inventor
Steven J. Woodward
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Canada Ltd
Federal Industries Industrial Group Inc
Original Assignee
Federal Industries Industrial Group Inc
Milltronics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB919120711A external-priority patent/GB9120711D0/en
Application filed by Federal Industries Industrial Group Inc, Milltronics Ltd filed Critical Federal Industries Industrial Group Inc
Publication of WO1993007601A1 publication Critical patent/WO1993007601A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
    • G—PHYSICS
    • G08—SIGNALLING
    • G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
    • G08C19/00—Electric signal transmission systems
    • G08C19/02—Electric signal transmission systems in which the signal transmitted is magnitude of current or voltage

Definitions

  • This invention relates to measuring instruments, namely process control transmitters for the continuous measurement and transmittal to a remote location of the value of a linear variable between presettable upper and lower limits, and is particularly although not exclusively applicable to echo-ranging instruments for measuring distances, for example from the top of a tank or silo to the surface of its contents.
  • Process control transmitters of the type referred to above are commonly installed as to provide monitoring of a particular variable, for example the depth of material in a tank, which may vary between predetermined limits determined by the tank dimensions and its particular installation.
  • a signal representing the value measured by the transmitter is to be transmitted to a remote location, it is desirable that upper and lower values of this signal not only do not fall too far beyond the span of the range to be measured, thus sacrificing resolution, but also that the signal value bears an accurately calibrated relationship to the value being measured.
  • a process control transmitter which measures a parameter and locally displays its value in fixed units, and also provides an electrical output signal whose magnitude varies linearly between minimum and maximum values in proportion to the variations of the measured parameter between first and second values.
  • the first value is set by causing the instrument to measure a desired minimum value of the parameter and to display a value accordingly, and selecting the displayed value as the first value
  • the second value is set by causing the instrument to measure a desired maximum value of the parameter, to display a value accordingly, and selecting the displayed value as the second value.
  • separate keys are utilized to enter each value.
  • the first and second values are associated with specific displayed values; whilst these displayed values may not accurately represent the absolute value of the parameter being measured due to offsets, or errors such as those discussed above, the minimum and maximum values of the output signal should continue to represent the absolute values of the parameter at the time of setting so that the output signal will vary in the desired manner.
  • Figure 1 is a simplified block diagram of a pulse- echo ranging system incorporating the invention.
  • Figure 2 shows a control panel of the system.
  • a transmitter 4 Under control of a microcontroller 2, a transmitter 4 generates pulses or shots of alternating current utilized to drive an acoustic transducer 6 aimed towards a surface whose movement is to be monitored. Typically this will be the surface 8 of a fluent solid or a liquid in a tank, bin or other vessel 10, above or at the top of which the transducer is mounted.
  • the alternating current pulses are converted by the transducer into acoustic energy which is projected towards the surface 8 and echoed back towards the transducer 6.
  • the transducer 6 is also connected to a receiver 12 through an interface circuit 14 which damps the transducer during the transmit pulse and limits the signal amplitude applied to the receiver.
  • the receiver filters and logarithmically amplifies the return echo signals which are digitized by an analog to digital converter 16 and applied to an input port of the microcontroller for further processing as described in the above mentioned U.S. patents.
  • the converter 16 is also used to process signals from a thermistor 50 associated with the transducer.
  • the microcontroller operates under control of a program stored in read only memory (ROM) 18, utilizing parameters stored in non ⁇ volatile random memory, in this example electrically erasable read-only memory (EEPROM) 20, random access memory (RAM) 22 providing working memory and temporary data storage.
  • ROM read only memory
  • EEPROM electrically erasable read-only memory
  • RAM random access memory
  • Data generated by the microcontroller 2 is displayed by a liquid crystal display 24 driven by output ports of the microcontroller, and is also output to a 4-20 ma interface 26 which converts digital output data from the microcontroller into analog current levels ranging between 4 and 20 milliamps.
  • the output produced by the interface 26 is suitable for transmission to a remote display, recording device or programmable controller adapted to operate with this type of interface. Whilst such an interface is widely adopted in industry, other standardized instrumentation interfaces could of course be used in place of that described.
  • User input to the microcontroller is limited to two push-buttons or keys 28 and 30 whose condition is sensed by input ports of the microcontroller, and a further output line from the controller controls an alarm relay 32 used to warn of abnormal conditions sensed by the microcontroller.
  • a suitable microcontroller is the 68HC11, available from Motorola, which in fact incorporates certain of the separately shown peripheral functions discussed above such as the converter 16, the EEPROM 20 and part of the RAM 22.
  • the display 24 consists simply of a three digit seven segment numerical display 38, and a logo, in this case a trade mark of the applicant, different segments 40 and 42 of which are independently controlled to provide various indications to the operator, supplemented by four auxiliary indicators 44, 46, 48 and 50.
  • the push-buttons 28 and 30 are labelled 20 and 4 respectively and located on a control panel 34 together with the display 24 and terminal block 36 providing output connections from the interface 26, power supply connections to the apparatus, and connections to the circuit controlled by the relay 32.
  • the control program of the microcontroller enters at START a main execution loop in which it controls the transmitter to cause the transducer to generate a shot or shots of acoustic energy, and processes the digitized echo signal from the A/D converter 16 to identify a true echo generally in accordance with the procedures of the prior patents identified above, and to determine the elapsed time from the beginning of the shot to the receipt of the echo ("measure echo time" in the Table) . The time is then converted to distance, utilizing stored data relating the speed of sound in air to temperature, as sensed by the thermistor 50, and this distance is displayed on the numeric display 38.
  • the distance displayed is based upon the distance between the transducer 6 and the surface 8, without compensation either for any offset between the transducer and the effective top level of the tank occasioned for example by the tank having a domed top, or for the transducer being mounted above or below the top of the tank, or any error due to the tank being filled with a vapour other than air. It does however provide verification to a user that the device is operating normally to determine ranges. For example, a very small constant reading on an empty or near empty tank, or despite varying levels, would be an indication that the device was responding to a strong spurious echo from structure near the top of the tank.
  • the program next relates the calculated distance to preset first and second distance values ee_4ma_dist and ee_20ma_dist defining a range span, and corresponding to 4 and 20 milliamp values respectively. Until these distance values are set as further described below, default values stored in EEPROM 20 are used defining a range which encompasses any likely distance reading.
  • the actual distance reading is translated to a milliamp value by linear interpolation between the preset distance values, and the digitized milliamp value generated is translated into an actual current in a current loop attached to the interface 26.
  • the program then tests the status of the keys 28 and 30 and if it detects a press of one or both keys enters different subroutines accordingly prior to returning to the beginning of the loop. If both keys are pressed, the "SET OTHER PARAMETERS" routine is entered. The seven segment display is caused to display the characters "*bL", the arrows representing turning on of the indicators 44 and 46. When the keys are released, the seven segment display then displays the blanking distance, i.e. the distance corresponding to a period following a shot during which the receiver signal is ignored for the purpose of identifying a true echo.
  • a default value of this distance is sufficient that ringing of the transducer following a shot has decayed to the point that the receiver is no longer saturated and can therefore respond to echo signals, but a larger value may be desirable if a strong short range spurious echo prevents proper operation of the instrument, as discussed above.
  • the routine waits for the keys to be released and then again tests the status of the keys. Unless both keys are pressed together, the displayed blanking distance it may be increased or decreased, as indicated by indicator 44 or 46, by pressing the key 28 or the key 30 respectively. If no keys are pressed for a predetermined period, the displayed value is stored in EEPROM 20 in place of the previously stored value, and then the display reverts to showing the measured distance.
  • the display shows "* c4" and then the value of ee 4ma dist when the keys are released, after which the keys 28 and 30 may be used to adjust this value as described above for the blanking distance. This enables the value to be set manually.
  • the display shows "c4", and the "measure echo time” and “convert time to distance” routines are performed. A check is then made as to whether a confidence factor, calculated as described in our prior patents, is sufficient for the echo to be considered reliable. If the echo is not reliable, a low echo indication is provided by causing the seven segment display to display the characters LOE, and the subroutine terminates. Otherwise, the measured target distance is displayed, and also written into EEPROM 20 as a new value of ee_4ma_dist, before the subroutine terminates.
  • both keys are pressed together whilst the blanking distance is displayed, the seven segment display is caused to display the characters SP, and then the value of a parameter ee_speed, which represents the rate at which distance measurements are made. According to application, a low rate may be desirable to avoid jitter, or a high rate so as to monitor rapid changes in the distance being monitored. The value of the parameter may then be set in the same manner as before. If desired, additional parameters may be set or reviewed the same way by again pressing both buttons at once. Once all parameters have been scanned, a further press of both keys returns execution to the beginning of the SET_OTHER PARAMETERS routine.
  • the logo segments 40 and 42 and the auxiliary indicators 44, 46, 48 and 50 are provided by various additional indications.
  • the segments forming the whole of the logo are turned on. Loss of a reliable echo is signified by the eye segments 40 of the logo being turned off, leaving only the pulse symbol segment 42 turned on.
  • the entire logo is turned off. Detection by the program of a fault in the operation of the instrument such as a memory error or failure to detect any response from the receiver will result in activation of the alarm relay 32 and also the indicators 48 and 50.
  • the indicator 46 is turned on, and during execution of the subroutine following pressing of the key 28, the indicator 44 is turned on.
  • the key 28 may be utilized to set a range or target distance which is either greater or less than the distance set by key 30. Assuming that the distances set represent maximum and minimum levels to be monitored in a tank using the key 28 to set the minimum level (i.e. the maximum target range) will result in an output representing the space remaining in the tank, whilst using it to set the maximum level (i.e. the minimum target range) will result in an output representing the degree of filling of the tank. This avoids the necessity for any separate control or input to initiate these two different functions.
  • One of the parameters which may be selected by the simultaneous pressing of both buttons could be a level which would result in energization of the alarm relay with the direction of alarm sensing depending on which key was used to make the final setting; or such a function could be initiated using an additional key.
  • additional keys however would compromise the essential simplicity of operation of the unit.
  • the two, upper and lower, operating keys instinctively represent upper and lower settings, and upward and downward directions of adjustment.
  • the primary data output of the instrument is that through the interface 26, and that it is this output which is being calibrated during the procedures discussed above.
  • No means is provided for calibration of the distances displayed by display 24; these are solely intended for operator guidance during the process of adjusting the output span, and represent the distance between the transducer and a target sensed by the transducer, assuming the intervening medium to be air.
  • the auxiliary indications are also intended for operator guidance.
  • the full display of the manufacturer's trademark during normal operation is a confirmation of this condition; such a full display will not occur if no reliable echo can be detected, or calibration is in progress.
  • upper and lower portions of the logo segments 40 could be separately controlled to indicate echoes out of range respectively beyond the limits set by the buttons 28 and 30, or to replace the indicators 44 and 46.
  • the invention can be used in echo or reflection ranging instruments using other forms of radiation sources such as infra-red lasers, or in other measurement applications.
  • a belt scale weight sensing device or a flowmeter may be similarly equipped to provide an analog signal to a remote integrator incorporated in a measurement or control device.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

Abstract

Un instrument de mesure, servant à transmettre un signal qui doit être lu à distance, comprend un affichage local (24) d'une valeur mesurée du paramètre en cours de mesurage, cet affichage interagissant avec un système d'étalonnage local à deux boutons (28, 30) dans lequel un bouton est utilisé pour établir chaque valeur limite d'une plage de valeurs devant être transmises par le signal à distance, ce qui permet d'étalonner et de régler la portée du signal. Les boutons peuvent être utilisés pour introduire des valeurs affichées de façon habituelle, ou alors, lorsqu'on presse en même temps les deux boutons, l'on peut introduire des modes de réglage selon lesquels un bouton augmente et l'autre réduit une valeur affichée d'un paramètre devant être introduit.
PCT/CA1992/000436 1991-09-30 1992-09-30 Systeme d'etalonnage pour instruments de mesure Ceased WO1993007601A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB919120711A GB9120711D0 (en) 1991-09-30 1991-09-30 Calibration system for measurement instruments
GB9120711.8 1991-09-30
CA2,058,356 1991-12-23
CA 2058356 CA2058356A1 (fr) 1991-09-30 1991-12-23 Systeme d'etalonnage pour instruments de mesure

Publications (1)

Publication Number Publication Date
WO1993007601A1 true WO1993007601A1 (fr) 1993-04-15

Family

ID=25674904

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA1992/000436 Ceased WO1993007601A1 (fr) 1991-09-30 1992-09-30 Systeme d'etalonnage pour instruments de mesure

Country Status (2)

Country Link
AU (1) AU2658192A (fr)
WO (1) WO1993007601A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2728337A1 (fr) * 1994-12-19 1996-06-21 Seikosha Kk Dispositif de mesure de distance
GB2341928A (en) * 1998-09-24 2000-03-29 London Electronics Limited Calibration of programmable digital meters
CN113494930A (zh) * 2020-04-06 2021-10-12 和辰企业股份有限公司 电感式传感器

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0097479A2 (fr) * 1982-06-17 1984-01-04 Honeywell Inc. Transducteur ajustable d'une variable de mesure
US4649527A (en) * 1984-08-03 1987-03-10 Siemens Aktiengesellschaft Ultrasonic proximity switch
WO1988001417A1 (fr) * 1986-08-22 1988-02-25 Rosemount Inc. Circuit transducteur analogique a commande numerique
WO1989002578A1 (fr) * 1987-09-17 1989-03-23 Square D Company Dispositif de commutation modulaire
US4831565A (en) * 1986-10-03 1989-05-16 Canadian Corporate Management Company Limited Process control equipment for adverse environments
US5083288A (en) * 1989-02-24 1992-01-21 Arpad Somlyody Apparatus for configuring a remote process sensor and signal transmitter

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0097479A2 (fr) * 1982-06-17 1984-01-04 Honeywell Inc. Transducteur ajustable d'une variable de mesure
US4649527A (en) * 1984-08-03 1987-03-10 Siemens Aktiengesellschaft Ultrasonic proximity switch
WO1988001417A1 (fr) * 1986-08-22 1988-02-25 Rosemount Inc. Circuit transducteur analogique a commande numerique
US4831565A (en) * 1986-10-03 1989-05-16 Canadian Corporate Management Company Limited Process control equipment for adverse environments
WO1989002578A1 (fr) * 1987-09-17 1989-03-23 Square D Company Dispositif de commutation modulaire
US5083288A (en) * 1989-02-24 1992-01-21 Arpad Somlyody Apparatus for configuring a remote process sensor and signal transmitter

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2728337A1 (fr) * 1994-12-19 1996-06-21 Seikosha Kk Dispositif de mesure de distance
GB2341928A (en) * 1998-09-24 2000-03-29 London Electronics Limited Calibration of programmable digital meters
CN113494930A (zh) * 2020-04-06 2021-10-12 和辰企业股份有限公司 电感式传感器

Also Published As

Publication number Publication date
AU2658192A (en) 1993-05-03

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