仪表考试题答案

1、仪表考试题答案One, the question:The higher the pressure, the smaller the structure of the bellows.The spring tube pressure gauge is designed to eliminate the gap between the transmission mechanism and reduce the variation of the instrument.The signal that the hall pressure transmitter is sent to the second

2、ary instrument is the voltage signal (the square root).The correct installation of the compensation conductor shall be applied from the thermocouple to the secondary instrument (square root).The pressure level can be used to measure exposure or the medium level of the sealed container (x).When the f

3、low rate is less than an hour, the inertia force of the fluid plays a leading role, and when the velocity is higher, the viscous force plays a leading role, (x)Heat exchange occurs when any metal object is exposed to two different temperatures, (fx)The thermodynamic temperature is the same as the Ce

4、lsius temperature, but the starting point is different, (fx)The drawback of integral adjustment is that there is a lag. (fx) Standard throttling devices do not need to be equipped to measure theviscous material and corrosive material, (x)The upstream and downstream of the throttling device do not ne

5、ed sufficient straight pipe length, (x)The electromagnetic flowmeter is not able to measure the flow of gas. (fx)The output current of the electromagnetic flowmeter is related to the cable relationship, (fx)The stroke of the stem is proportional to the size of the input signal of the valve locator,

6、(fx)The ratio of the proportional integral controller can greatly increase the stability of the system, (x)The signal line of the electromagnetic flowmeter is not allowed to be worn in a pipe with the power cord, (fx)The protective tube is used to protect the thermocouple from chemical corrosion and

7、 mechanical damage, (fx)The standard orifice is used in both directions to measure the flow, (x)The accuracy rating of the instrument is based on the relative error (square root).Use the forbidden oil in the oxygen piping. The acetylene pressure gauge can be used for copper sealing pads (x).The maxi

8、mum pressure line should not be greater than 50 meters. National regulations (standard) slope 1:10 1:10 (square root)In order to make the flow coefficient of the orifice flowmeter constant, the Reynolds number of the fluid should be greater than the limit of the Reynolds number (square root).The rat

9、io of the inertia force of thefluid to the viscous force iscalled the Reynolds number. The flow rate is a laminar state when Rt is less than 40, 000. Rt > 2300 (x) for turbulent stateEpsilon for compressible medium epsilon = 1: For the incompressible medium epsilon < 1 (x)The K is not equal to

10、 1 for the ideal gas. For the actual gas K = 1 (x)Differential pressure transmitter and throttling device. The pipe length between the pressure points of the liquid level shall be within50 meters. The inner diameter of the guide tube shall be less than that of the 8mm guide pipe level. When measurin

11、g liquid or steam, exhaust or blow-down valve should be installed at the highest and lowest point of the catheter system.The orifice Angle is not sharp, the flow system is smaller (x).When the differential pressure is large, the pressure loss of the throttle is small (x).29, with a throttling device

12、 measuring wet dry gas of volume flow (standard condition) if the work condition of relative humidity than the design increases, this is the instrument of instructions will be bigger than the real value (fx)The pipe will carry the orifice in the opposite direction, and the differential pressure gaug

13、e will be smaller (square root).The metal rotameter must be installed horizontally (x).Because the metal rotor flowmeter must be installed vertically, the flow direction can be either down or down.33, electromagnetic flow meter power supply line and Central Line, the excitation winding line and Cent

14、ral Line and the transmitter output signal terminal 1. 2 is impossible to free exchange (fx)The ultrasonic flowmeter can measure the liquid. The flow of the gas is non-conductive medium and it is not subject to fluid pressure. Temperature. Viscosity.35, nuclear scale materials for non-contact measur

15、ement, not affected by the temperature of the material. Such as corrosive effect, also from the belt tension. Vibration. Inertia force. Such as running wide influence (fx)Since the hole plate is suitable for measuring the fluid that may produce sediment before and after the orifice, it is the standa

16、rd throttle unit (x).The thermoelectric temperature measurement is due to the use of the compensation conductor, so it has the effect of cold end temperature compensation (x).38, with a platinum rhodium - platinum thermocouple temperature furnace temperature, in the absence of other compensation cas

17、es, the measured thermoelectric potential of 10. 63 mv (look-up table is1093 ° C, the free end temperature of 50°C (table 0. 799 mv) socould discern furnace the actual temperature of 1093°C to + 50 °C =1143 °C (x)The axial position of the two electrodes is not required (x) b

18、ecause the full tubular electromagnetic flowmeter can be installed vertically or inclined.The optimal location of the electromagnetic flowmeter on the pipe is the suction side of the pump (x).The degree of the nickel-nickel silicon thermocouple is S (x).The reason for the negative jump of the electr

19、omagnetic flowmeter when the flow is positive is 1. 2 signal line reverse (x).Most of the automatic control systems are negative feedback (square root)The current signal 4-20mA has a greater load resistance than 0-10 mA. (X)45, the pressure loss that flows through the throttling device can be fully

20、recovered. (X)The protection level IP20 is higher than the IP54. (X)The instrument number, the us-xxx, indicates the control of the position display. (X)The number of 48, 10 A/D transformations is 512. (X)For a digital instrument, a double integral transform, if its voltage reference is low, the dis

21、play value is small. (X)50, with B dividing thermocouple, when the environment temperature is less than 10 0 °C, can need not compensation conductor. (Y)51, electric current output terminal load resistance Q or higher. (X)The output resistance of the resistance strain plate weighing sensor is g

22、enerally greater than the input resistance. (X)A/D converter is mainly used to convert digital signals into analog signals. (X) 54, the sample is used in the same period of ImS high precision multimeter, can be accurately measured, the frequency is 1000HZ signal. (X)Generally speaking, increased loa

23、d is the output power of the circuit and the power supply increases, (fx) 56, the reference point of the potential value of a point in the circuit is independent of reference point. (X)The choice plus theorem applies only to linear circuits, which can be used to calculate the amount of linear relati

24、onships, such as voltage and current, but cannot be used to calculate power. Because power is a quadratic function of current (or voltage), it is not linear, (fx)5A, the maximum value of the ac current is 5A. (X)The ac voltage at both ends of the communication element lags behind the current flowing

25、 through it, and the component is a capacitive load, (fx)The line voltage of the three-phase winding for the star join of the three-phase winding is equal to the line voltage when the three-phase winding is a triangle connection. (X)The closer the third phase load gets to the symmetry, the smaller t

26、he midline current, (fx)The total power of a three-phase symmetrical load is equivalent to a triangle or star join in the same power supply voltage.(X)The transistor is made of two PN structures, so it is possible to use two diodes to connect to the transistor. (X)The reverse current is small when t

27、he diode is added to the reverse voltage, so the collector current must be very small when the transistor's collector junction plus the reverse voltage. (X)65, when the secondary tube is positive, the higher the voltage, the smaller the equivalent impedance gamma VD, so the current IVD is larger

28、, (fx)Since the diode has a bit effect, the diode can be equivalent to anEVD = 0. 7 voltage source under the positive signal, (fx)67, when it's a resistive load,Single-phase bridge semi-controlled rectifier circuit twice as much as a single phase half wave rectifier circuit, (fx)The pressure tra

29、n smitter sends a pressure to the sec on dary in strume nt.(X)Measuri ng the orifice of the orifice, if the direct ion is reversed,the differential pressure indicator is smaller, (fx)The nu clear scale has bee n calibrated to weigh any material effect. (X)771. The bending radius should not be greate

30、r tha n 10 D whe n coveri ngthe cable, (fx)Whe n in stalli ng orifice plates, the flange must be perpe ndicular tothe pipe, and the divid ing line is concen tric, (fx)The den sity of the liquid is equal to the ratio of mass m divided byvolume, which is kilograms over m3, (fx)The key component of the

31、 stabilized voltage supply is the stabilizer,(square root)The accuracy grade of the in strume nt is divided accord ing to relative error, (fx)In the case of a digital instrument, a double integral transform, ifits voltage reference is low, the display value is small.(X)The in put voltage of 77-3 sta

32、bilizer 7915 is arou nd 15V. (X)The 78 and the decimal number 1A is equal to the decimal number 26. (Y)A n eutr on moisture meter cannot be used for measureme nt of an object with a carbohydrate. (Y)In the thermocouple temperature circuit, we can only consider the thermoelectric potential. (Y)Electr

33、omagnetic flowmeter is widely used in the measurement of sanitary water. (X)The general nuclear scale is calibrated by checkboard and the belt scale is calibrated. (X)The international temperature is equivalent to the thermodynamic temperature scale. (Y)884, the protective casing of thermocouple met

34、al is more durable than non-metal protective casing. (X)The thermoelectric resistance can be connected to two instruments at the same time for temperature display. (X)86, 1 mb ar is equal to 10 pa. (X)Smart meters are field bus meters (X).The difference between the same accuracy and the same precisi

35、on can be replaced by two pressure changes. (X)The low resistance box is available as a voltage source (X).The interface RS232C input output is TTL level. (X)The output resistance of the resistance strain plate weighing sensor is generally greater than the input resistance. (X)A/D converter is mainl

36、y used to convert digital signals into analog signals. (X)The sample is used in ImS in the same period, and can be measured accurately with a frequency of 1000HZ. (X)The assembly language is only compiled by machine code. (X)The content in the ROM is readable, and the content in RAM is readable. (X)

37、The hard drive is placed inside the main box, the internal memory. (X)The basic unit of hard disk memory reads and writes is bytes. (X)Ethernet adopts the CSMA/CD protocol. (Y)The biggest advantage of computer networks is the sharing of resources. (Y)When the user applies for an Internet account, th

38、e user，s E-mailaccount includes the IP address and user password. (X)A compensation conductor that matches a thermocouple, which, when connected, causes the secondary instrument to be smaller if the polarity is reversed, (a)Answer:)At the same temperature variation, the heat resistance of the index

39、is greater than the thermal resistance of the dielectric resistance, and therefore the sensitivity is high, (a)Answer:) The characteristic of platinum thermoelectric resistance is the stability and the linear degree of resistance temperature.(a)Answer: *104, thermocouple compensating wire and thermo

40、couple cold end compensator, the effect of temperature in temperature measurement is the same, it is to compensate for the thermocouple cold terminal temperature, (a)Answer: *The smaller the flow, the smaller the measurement error when using throttling flowmeter, (a)Answer: *106, compensation conduc

41、tor can only be used with dividing the same number of thermocouples, usually its junction temperature below 100 °C. (a)Answer:)The use of zirconium oxide is used to measure the amount of oxygen in a single component, and the input impedance of the secondary instrument should not be too large, (a)Answer:108. When measur