1、BRITISH STANDARD BS6447:1984 Incorporating Amendment No.1 Specification for Absolute and gauge pressure transmitters with electrical outputs UDC 621.316.79:531.787:532.11BS6447:1984 This British Standard, having been prepared under the directionof the Industrial-process Measurement and Control Stand
2、ards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31January1984 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference PCL/1 Draft for comment 81/25629 DC ISBN 0 580 13649 3 Committees responsible for this British
3、Standard The preparation of this British Standard was entrusted by the Industrial-process Measurement and Control Standards Committee (PCL/-) to Technical Committee PCL/1 upon which the following bodies were represented: British Gas Corporation British Industrial Measuring and Control Apparatus Manu
4、facturers Association (BEAMA) British Pressure Gauge Manufacturers Association Department of Energy, Gas Standards Electricity Supply Industry in England and Wales Energy Industries Council Engineering Equipment and Materials Users Association Institution of Gas Engineers National Coal Board Scienti
5、fic Instrument Manufacturers Association (BEAMA) STC Water Regulations and Fittings Scheme The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Valve Manufacturers Association Ltd Department of Trade and Industry Department of Trade an
6、d Industry, National Physical Laboratory Department of Trade and Industry, National Engineering Laboratory Metals Society Ministry of Defence Sira Limited Amendments issued since publication Amd. No. Date of issue Comments 5223 September 1986 Indicated by a sideline in the marginBS6447:1984 BSI 07-1
7、999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Classification 1 4 Performance 2 5 Materials and construction 4 6 Marking 5 Annex A Methods of test 6 Table 1 Limits of combined error 2 Table 2 Limits of zero shift and span change with temperature
8、, andlimitsofresidual changes after temperature excursions 2 Table 3 Over-range pressure 4 Table 4 Limits of average long-term drift 4 Table 5 Atmospheric conditions for reference measurements 6 Table 6 Frequency ranges for evaluation 9 Publications referred to Inside back coverBS6447:1984 ii BSI 07
9、-1999 Foreword This British Standard has been prepared under the direction of the Industrial-process Measurement and Control Standards Committee. The SI pressure unit “pascal” has been used throughout this standard. However, since a large sector of British industry is committed to the use of the pre
10、ssure unit “bar” and intends to maintain this position, the equivalent in bars has been given in brackets after the value in pascals. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. C
11、ompliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may ha
12、ve had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6447:1984 BSI 07-1999 1 1 Scope This British Standard specifies requirements for d.c. powered electrical transmitters with analogue direct current output used in absolute and gauge pressure meas
13、urement. This specification applies to transmitters for general industrial use but does not apply to aerospace, marine, laboratory and medical requirements. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Bri
14、tish Standard the following definitions apply. 2.1 measured error the largest deviation of the output of the transmitter from its corresponding ideal value, obtained with both increasing and decreasing inputs NOTEMeasured error is expressed as a percentage of span and is determined in accordance wit
15、h the method described in A.2.2. 2.2 hysteresis that property of an element evidenced by the dependence of the, value of the output, for a given excursion of the input, upon the history of prior excursions and the direction of the current traverse NOTEThis is a common usage definition which includes
16、 hysteresis error and dead band. That portion of the difference which is dependent on the history of prior excursion is hysteresis error while that portion due to dead band may be determined by a conventional dead band test. 2.3 hysteresis error that portion of hysteresis due to energy absorption in
17、 the elements of a measuring instrument NOTEHysteresis error should be determined by subtracting the value of dead band from the maximum measured separation between upscale-going and downscale-going indications of the measured variable, during a full-range traverse unless otherwise specified. 2.4 de
18、ad band the largest change in input that can be effected without causing a detectable change of output 2.5 range the region between the limits within which a quantity is measured, received or transmitted, expressed by stating the lower and upper range values 2.6 lower range value the lowest value of
19、 the measured variable that a device is adjusted to measure 2.7 upper range value the highest value of the measured variable that a device is adjusted to measure 2.8 span the algebraic difference between the upper and lower range values 2.9 over-range the condition in which any value of the input si
20、gnal exceeds its upper range value or goes below its lower range value 2.10 repeatability the closeness of agreement among a number of consecutive measurements of the output for the same value of the input under the same operating conditions, approaching from the same direction, for full-range trave
21、rses 2.11 transmitter a measuring transducer whose output is a standardized signal 2.12 absolute pressure an indication of pressure based on a zero at total vacuum 2.13 gauge pressure an indication of pressure based on a zero at the ambient atmospheric pressure 3 Classification 3.1 General. The perf
22、ormance characteristics of transmitters are classified as follows: a) accuracy (see Table 1); b) temperature coefficient (see Table 2).BS6447:1984 2 BSI 07-1999 The performance characteristics shall be identified by a two-element code in the above order, followed by the range of the transmitter with
23、in which the characteristics apply. Example: 3.2 Adjustable range transmitters. For adjustable range transmitters the performance characteristics shall be identified by two-element codes as specified in 3.1 appropriate to ranges corresponding at least to the maximum and minimum spans. Example: 4 Per
24、formance 4.1 General. Reference conditions shall be as given in A.1. 4.2 Accuracy. When tested in accordance with the method described in A.2 the combined error given by the sum of the modulus of the measured error and the repeatability, under reference conditions shall not exceed the values given i
25、n Table 1. NOTE 1For the first60min after the power supply is switched on, these requirements do not apply because of the possible effect of start-up drift. Table 1 Limits of combined error NOTE 2The requirements of 4.5.2.2, 4.5.2.4, 4.9.3, 4.11 and4.12 need to be taken into account in determining t
26、he accuracy class given in Table 1. NOTE 3The error of a local output current indicator, if fitted, is not included in the calculation of the error of the transmitter. 4.3 Temperature variations 4.3.1 General. The transmitter shall be capable of continuous operation within an ambient temperature ran
27、ge of25 C to+70 C. 4.3.2 Effect of temperature variations. The effect of temperature variations shall be tested in accordance with the method described in A.3. At any temperature between 25 C and+70 C the average coefficients of zero shift and span change relative to20 C each shall not exceed the va
28、lues given in Table 2. Table 2 Limits of zero shift and span change with temperature and limits of residual changes after temperature excursions After a temperature excursion from20 C to any temperature between 25 C and+70 C, the residual zero shift and span changes each shall not exceed the values
29、given in Table 2. 4.4 Humidity 4.4.1 General. When tested in accordance with the methods described in A.4 and A.5 the transmitter shall be capable of continuous operation at a relative humidity up to95%. 4.4.2 Effect of relative humidity variations. There is no additional requirement specified for a
30、 variation in relative humidity. When the transmitter is subjected to the test described in A.4, the errors shall not exceed the values given in Table 2. When the transmitter is subjected to the test with covers off, described in A.5, the errors shall not exceed the values given in Table 2. 4.5 Elec
31、trical characteristics 4.5.1 Output circuit 4.5.1.1 General. The electrical output of the transmitter shall have a range of4mA to20mAd.c., or0mA to20mA d.c. The transmitter shall be capable of operation when the output terminals are isolated from earth and when either terminal is earthed. 0.5A 0 kPa
32、 to200 kPa absolute (0 bar to2 bar absolute) a 0.5A 0 MPa to10 MPa gauge (0 bar to100 bar gauge) a 1 bar=10 5N/m 2 =100 kPa. 1) 0.5A 0 kPa to200 kPa absolute (0 bar to2 bar absolute) 1B 0 kPa to25 kPa absolute (0 bar to0.25 bar absolute) 2) 0.5A 0 MPa to10 MPa gauge (0 bar to100 bar gauge) 1B 0 MPa
33、to1 MPa gauge (0 bar to10 bar gauge) Accuracy class Limits of combined error 0.2 0.5 1.0 2.0 5.0 % of output span 0.2 0.5 1.0 2.0 5.0 Temperature coefficient class Limits of zero shift and span change Limits of residual zero shift and span change A B C D E % of output span per C 0.005 0.010 0.020 0.
34、050 0.100 % of output span 0.05 0.10 0.20 0.50 1.00BS6447:1984 BSI 07-1999 3 4.5.1.2 Ripple and noise. The peak-to-peak value of internally generated ripple and noise appearing in the output current shall not exceed the value given in Table 1 up to a maximum of1% of the output span, in a frequency r
35、ange of zero to100kHz. The appropriate test shall be performed by measurement of the peak-to-peak ripple content of the output with10%, 50% and90% input signals at minimum and maximum resistive load. 4.5.1.3 Stability. The output of the transmitter shall be stable and the ripple shall comply with 4.
36、5.1.2 when the manufacturers recommended maximum resistive load is shunted by any capacitance up to a maximum of14F. 4.5.1.4 Effect of earthing output. When tested in accordance with the method described in A.6 the change in output owing to an earth connection shall not exceed0.25% of the output spa
37、n. 4.5.2 Power supply and load 4.5.2.1 General. Both two-wire and three-wire transmitters shall be capable of continuous operation from a d.c. supply with any value from20V to30V. Two-wire transmitters shall be capable of supplying current to a resistive load between07 and at least3007. Three-wire t
38、ransmitters shall be capable of supplying current to a resistive load between07 and at least5007. NOTE 1In some circumstances, e.g.in intrinsically safe systems, the use of higher external resistive loads may be negotiated between the supplier and the user. NOTE 2For two-wire transmitters, the outpu
39、t signal is carried on the same pair of wires that provide the power supply. For three-wire transmitters one wire is common to the power supply and the output signal. 4.5.2.2 Effect of power supply variations. The change in output as the voltage is varied from20V to30V, with a load of3007 for two-wi
40、re transmitters, or5007 for three-wire transmitters, shall not exceed0.1% of the output span for accuracy class0.2, 0.2% of the output span for accuracy classes0.5, 1 and2, and0.5% for accuracy class5. The appropriate test shall be performed with the input pressure adjusted to the value required to
41、give full range output. 4.5.2.3 Supply aberrations. After supply interruptions are applied to the transmitter under the conditions described in A.7 the transmitter shall be capable of continuous operation in accordance with4.2. 4.5.2.4 Load resistance. When the load resistance is varied from zero to
42、 maximum, and vice versa at any fixed supply voltage between20V and30V, the total variation in output current shall not exceed0.1% of the output span for accuracy class0.2, 0.2% for accuracy classes0.5, 1 and2 and0.5% for accuracy class5. 4.5.3 Interference 4.5.3.1 Variations in the mean d.c. level
43、of the output current, due to spurious signals of up to250V50Hz and50V d.c. in common mode when tested in accordance with the method described in A.8, or1V50Hz in series mode, when tested in accordance with the method described in A.9 shall not exceed0.1% of the output span at any output value. The2
44、50V a.c. common mode signal shall be derived from a source with an impedance of between0.5M7 and10M7. 4.5.3.2 When tested in accordance with the method described in A.10 variations in the mean d.c. level of the output current, due to a spurious signal of50mA50Hz along the length of screen, shall not
45、 exceed0.1% of the output span at any output value. 4.5.3.3 For transmitters stated by the manufacturer to be suitable for use in the presence of r.f. interference, the transmitter shall be capable of operation in the presence of electromagnetic radiation of field strength10V/m in any orientation wi
46、th respect to the field and at frequencies in the following ranges: 27MHz to28MHz 68MHz to88MHz 100MHz to108MHz 138MHz to174MHz 420MHz to470MHz The change in output owing to application of the field shall not exceed1% of the output span. NOTE 1No test is specified for this requirement. The manufactu
47、rer should be consulted for the appropriate test. NOTE 2For the purpose of testing, the output should be set to50% of span. 4.6 Pressure 4.6.1 Over-range pressure. The pressure transmitter shall be capable of withstanding the over-range pressure given in Table 3. When tested in accordance with the m
48、ethod described in A.11, the residual zero shift and span change each shall not exceed one quarter of the values of the limits of error given in Table 1 for the accuracy class of the transmitter.BS6447:1984 4 BSI 07-1999 4.7 Mounting position. When tilted at an angle of up to10 in any direction from
49、 the manufacturers normal recommended mounting position, the transmitter shall be capable, after any necessary zero adjustment, of continuous operation in accordance with 4.2. 4.8 Mechanical shock. Transmitters shall be capable of withstanding mechanical shock of the severity described in A.12. Table 3 Over-range pressure 4.9 Vibration 4.9.1 General. Transmitters shall be capable of withstanding vibration of the severity described inA.13. For the test performed with power applied to the transmitter, the input sh
