1、BRITISHSTANDARD BS6174:1982 Incorporating Amendment No.1 Specification for Differential pressure transmitters with electrical outputs UDC 621.317.39:531.787.91BS6174:1982 This BritishStandard, having been prepared under the directionof the Industrial-process Measurementand ControlStandards Committee
2、 waspublished under the authorityof the Board of BSI andcomes into effect on 26February1982 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference PCL/1 Draft for comment 74/27963 DC ISBN 0 580 12411 8 Cooperating organizations The Industrial-process Measur
3、ement and Control Standards Committee, under whose direction this BritishStandard was prepared, consists of representatives from the following: British Gas Corporation* British Industrial Measuring and Control Apparatus Manufacturers Association* British Steel Corporation Control and Automation Manu
4、facturers Association (BEAMA) Department of Industry Department of Industry (Computers Systems and Electronics) Department of Industry (National Engineering Laboratory) Department of the Environment (Water Engineering Division including Water Data Unit) Electrical, Electronic, Telecommunications and
5、 Plumbing Union Electricity Supply Industry in England and Wales* Energy Industries Council* Engineering Equipment Users Association* Institute of Measurement and Control* Institution of Gas Engineers* Oil Companies Materials Association* Post Office Engineering Union Scientific Instrument Manufactu
6、rers Association* Sira Institute The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this BritishStandard: British Pressure Gauge Manufacturers Association Chemical Industries
7、 Association Department of Energy Gas Standards National Coal Board Amendments issued since publication Amd. No. Date of issue Comments 5222 September 1986 Indicated by a sideline in the marginBS6174:1982 BSI 12-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1
8、2 References 1 3 Definitions 1 4 Classification 1 5 Performance 2 6 Materials and construction 4 7 Marking 5 Appendix A Test methods 6 Table 1 Limits of combined error 2 Table 2 Limits of zero shift and span change with temperature, andlimitsofresidual changes after temperature excursions 2 Table 3
9、Limits of zero shift and span change with pressure 3 Table 4 Limits of residual changes after pressure excursions 4 Table 5 Limits of average long-term drift 4 Table 6 Atmospheric conditions for reference measurements 6 Table 7 Frequency ranges for evaluation 9 Publications referred to Inside back c
10、overBS6174:1982 ii BSI 12-1999 Foreword This 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 t
11、he use of the pressure 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 corre
12、ct application. Compliance 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
13、 date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6174:1982 BSI 12-1999 1 1 Scope This BritishStandard specifies requirements ford.c. powered electrical transmitters with analogue direct current output used in differential pres
14、sure measurement. This standard applies only to transmitters with a linear relationship between differential pressure input and current output for general industrial use, and does not apply to aerospace, marine, laboratory and medical requirements. 2 References The titles of the publications referre
15、d to in this standard are listed on the inside back cover. 3 Definitions For the purposes of this standard the following definitions apply. 3.1 measured error the largest deviation of the output of the transmitter from its corresponding ideal value, obtained with both increasing and decreasing input
16、s NOTEMeasured error is expressed as a percentage of span and is determined in accordance with A.2.5. 3.2 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 c
17、urrent traverse NOTEThis is a common usage definition which includes 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 attributable to dead band may be determined by a conventional dead band test
18、. 3.3 hysteresis error that portion of hysteresis attributable to energy absorption in 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
19、the measured variable, during a full-range traverse unless otherwise specified. 3.4 dead band the largest change in input that can be effected without causing a detectable change of output 3.5 range the region between the limits within which a quantity is measured, received or transmitted expressed
20、by stating the lower and upper range values 3.6 lower range value the lowest value of the measured variable that a device is adjusted to measure 3.7 upper range value the highest value of the measured variable that a device is adjusted to measure 3.8 span the algebraic difference between the upper a
21、nd lower range values 3.9 over-range the condition in which the value of the input signal exceeds its upper range value or goes below its lower range value 3.10 repeatability the closeness of agreement among a number of consecutive measurements of the output for the same value of the input under the
22、 same operating conditions, approaching from the same direction, for full-range traverses 3.11 transmitter measuring transducer whose output is a standardized signal 4 Classification The performance characteristics of transmitters are classified under four headings as follows: a) accuracy class; b)
23、temperature coefficient class; c) static pressure class; d) over-range class. For fixed range transmitters the performance characteristics shall be identified by a four-element code in the above order (seeTable 1to Table 4), followed by the range of pressure within which the characteristics apply. F
24、or example:0.5A3B,0kPa to200kPa (0bar to2bar)BS6174:1982 2 BSI 12-1999 For adjustable range transmitters the performance characteristics shall be identified by four-element codes appropriate to ranges corresponding at least to the maximum and minimum spans. For example: 0.5A3B0kPa to200kPa(0bar to2b
25、ar) 1B3C0kPa to25kPa(0bar to0.25bar) 5 Performance 5.1 Reference conditions. Reference conditions shall be as given inA.1. 5.2 Accuracy. When tested in accordance with A.2 the combined error given by the sum of the modulus of the measured error and the repeatability, under reference conditions shall
26、 not exceed the values given in Table 1. Table 1 Limits of combined error NOTE 1The requirements of5.5.2.2, 5.5.2.4, 5.9.3, 5.11 and5.12 need to be taken into account in determining the accuracy class given in Table 1. NOTE 2The error of a local output current indicator, if fitted, is not included i
27、n the calculation of the error of the transmitter. 5.3 Temperature variations 5.3.1 General. The transmitter shall be capable of continuous operation within an ambient temperature range of25 C to+70 C. 5.3.2 Effect of temperature variations. The effect of temperature variations shall be tested in ac
28、cordance withA.3. At any temperature between25 C and+70 C the average coefficients of zero shift and span change relative to20 C each shall not exceed the values given in Table 2. Table 2 Limits of zero shift and span change with temperature, and limits of residual changes after temperature excursio
29、ns After a temperature excursion from20 C to any temperature between25 C and+70 C, the residual zero shift and span changes each shall not exceed the values given in Table 2. 5.4 Humidity 5.4.1 General. When tested in accordance withA.4 the transmitter shall be capable of continuous operation at a r
30、elative humidity of up to95%. This also applies for periods of up to4h with the adjustment covers removed. 5.4.2 Effect of relative humidity variations. There is no additional change specified for a variation in relative humidity. When the transmitter is subjected to the test described inA.4, the er
31、rors shall not exceed the values given in Table 2. When the transmitter is subjected to the test with covers off described inA.5, the errors shall not exceed the values given in Table 2. 5.5 Electrical characteristics 5.5.1 Output circuit 5.5.1.1 General. The electrical output of the transmitter sha
32、ll have a range of4mA to20mA d.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. 5.5.1.2 Ripple and noise. The peak-to-peak value of internally generated ripple and noise appearing in the output
33、current shall not exceed the values stated in Table 1 up to maximum of1% of the output span over a frequency range 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 resisti
34、ve load. 5.5.1.3 Stability. The output of the transmitter shall be stable and the ripple shall comply with the requirement of5.5.1.2 when the manufacturers recommended maximum resistive load is shunted by any capacitance up to a maximum of14F. 5.5.1.4 Effect of earthing output. When tested in accord
35、ance withA.6 the change in output owing to an earth connection shall not exceed0.25% of the output span. 5.5.2 Power supply and load 5.5.2.1 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 transmitt
36、ers shall be capable of supplying current to a resistive load between07 and at least3007. Three-wire transmitters shall be capable of supplying current to a resistive load between07, and at least5007. Accuracy class Limits of combined error, % of output span 0.1 0.2 0.5 1.0 2.0 5.0 0.1% 0.2 0.5 1.0
37、2.0 5.0 Temperature coefficient class Limits of zero shift and span change, %of output span per C Limits of residual zero shift and span change, % of output span A B C D E 0.005 0.010 0.020 0.050 0.100 0.05 0.10 0.20 0.50 1.00BS6174:1982 BSI 12-1999 3 NOTE 1In some circumstances, e.g.in intrinsicall
38、y safe systems, the use of higher external resistive loads may be negotiated between the supplier and user. NOTE 2For two-wire transmitters, the output 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 t
39、he output signal. 5.5.2.2 Effect of power supply variations. The change in output as the voltage is varied from20V to30V, with a load of3007, for two-wire transmitters, or5007, for three-wire transmitters, shall not exceed0.05% of the output span for accuracy class0.1,0.1% for accuracy class0.2,0.2%
40、 for accuracy classes0.5,1 and 2 and0.5% for accuracy class5. The appropriate test shall be performed with the input pressure adjusted to the value required to give full range out-put. 5.5.2.3 Supply aberrations. After supply interruptions are applied to the transmitter under the conditions specifie
41、d inA.7 the transmitter shall be capable of continuous operation in accordance with5.2. 5.5.2.4 Load resistance. When the load resistance is varied from07, to maximum, and vice versa at any fixed supply voltage between20V and30V, the total variation in output current shall not exceed0.05% of the out
42、put span for accuracy class0.1,0.1% for accuracy class0.2,0.2% for accuracy class0.5,1and2 and0.5% for accuracy class5. 5.5.3 Interference 5.5.3.1 Variations in the mean d.c. level of the output current, due to spurious signals of up to250V50Hz and50V d.c. in common mode, when tested in accordance w
43、ithA.9, or1V50Hz in series mode, when tested in accordance withA.10, shall not exceed0.1% of the output span at any output value. The250V a.c. common mode signal shall be derived from a source with an impedance between0.5 M7 and10M7. 5.5.3.2 For transmitters consisting of two or more separate units
44、connected by a screened cable, variations in the mean d.c. level of the output current, due to a spurious signal of50mA50Hz along the length of screen, shall not exceed0.1% of the output span at any output value. The appropriate test shall be performed as follows. Set the output to50% of span. Isola
45、te one of the instrument cases from earth, and pass a current of50mA,50Hz square wave through the cable screen. Measure any change of the output. 5.5.3.3 For transmitters stated by the manufacturer to be suitable for use in the presence of r.f. interference, the transmitter shall be capable of opera
46、tion in the presence of electromagnetic radiation of field strength10V/m in any orientation with 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 n
47、ot exceed1% of the output span. For the purpose of testing, the output is set to50% of span. The manufacturer shall state the method of test employed to check compliance with these requirements. 5.6 Pressure 5.6.1 Static (process) pressure. When the static pressure applied to the transmitter is vari
48、ed from atmospheric pressure to the manufacturers limit or to10MPa (100bar) whichever is less, under the conditions specified inA.1, the average coefficients of zero shift and span change relative to conditions at atmospheric pressure each shall not exceed the values given in Table 3. For a transmit
49、ter for use where the static pressure is reduced below atmospheric pressure, the change in output shall not exceed0.1% of the output span. Table 3 Limits of zero shift and span changewith pressure 5.6.2 Over-ranging. The residual zero shift and span change, due to the application of an asymmetrical input pressure in either direction up to the maximum static pressure specified by the manufacturer under the conditions given inA.12, shall not exceed the values given in Table 4. 5.7 Mounting position. When tilted at
