JPS5838816A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To obtain interchangeability between an oscillator and converter, by making the dispersion in a signal electromotive force generated on the oscillator side as a constant for the oscillator, and compensating for the signal electromotive force by said constant at the converter side. CONSTITUTION:The oscillatorIoutputs the signal electromotive force which is generated across electrodes 3 and 3a when fluid to be measured flows through the magnetic field formed by supplying an exciting current through an exciting coil 1. The intrinsic current K of the oscillatorIis expressed by K=ets/ess, where ess is the standard signal electromotive force of a standard oscillator and ets is signal electromotive force of the ordinary oscillatorIunder the same conditions. The full scale flow rate 1 is set in a flow rate setting part 15a of a setting part 15 in the converter II, and, at the same time, the intrinsic constant K of the oscillatorIwhich is combined to a meter setting part 15b is set in the meter setting part 15b. In the converter II, the signal electromotive force, which is inputted to the converter II from the oscillatorI, is multiplied or divided by the constant K and outputted. In this way, the interchangeability between the oscillator and the converter can be obtained.

Description

[Detailed Description of the Invention] This Act I14 relates to an electromagnetic flowmeter, and can be ensured in terms of compatibility between a transmitter and a converter. The electromagnetic flow needle has a conductive #! point perpendicular to the magnetic field. Body [1 liter flushed
Generates an electromotive force with a thickness corresponding to the flow velocity generated between KtW, and thereby increases the flow rate! This is the ninth thing that I have determined.
The 0 and 1 converters are composed of a transmitter that generates the electromotive force and a converter that converts the weak flow signal from the transmitter into a mains 61 signal or a pulse train signal. There is a resistor for gain adjustment associated with the scale, and if the output characteristics of the oscillator are constant, for example, when the flow rate is y-1111114, the output voltage -IJ
Unfortunately, if the full span flow rate changes from, for example, 100 to 120 to noodles, the converter output will be the same value, for example 4V at full span flow rate.
However, even if the conversion I) 0 gain key Il is perfect, the characteristics of the oscillator side are stingy and the converter's 1! If it does not match the desired characteristics, an error will occur in the output signal Kit of the converter. Variations in the characteristics of such transmitters include, for example, variations in diameter during manufacture,
Excitation coil 01! This may simply occur due to variations in the number of coils and the state of the #certain coil 0* attached. In the prior art KsP, the variation in the characteristics of the generator is removed by adjusting the total excitation current, and the excitation current value tIl is displayed on the plate, etc., thereby ensuring compatibility between the two. That is, for example, when the reference V is 1 mK+, the output signal of the oscillator is 1 m
Keep the excitation current constant for each transmitter and write it down on the nameplate, and adjust the excitation current to the excitation current value of 1m to be supplied to the generator using an arbitrary converter. However, in this method of increasing the excitation current, it would be a good idea to design the transmitter to generate a constant signal electromotive force for a constant flow velocity. However, in the case of a micro-diameter electromagnetic flow needle and a large-diameter electromagnetic flow needle, the required aim current increases, power consumption increases, and the size and weight of the IIJ Ususa circuit increase. Put it away,
In the case of #i, the same magnetic flux 12Ff is proportional to the electromotive force 11, which is 9%, and in the latter case, the magnetic flux 91 degrees is proportional to the square of the diameter. This is because the conventional alfK>- requires a circuit to precisely set the excitation current value, which has the drawback of requiring multiple circuit configurations. AFi, in view of the above-mentioned shortcomings of the prior art, aims to provide an electric 1m flow needle that can eliminate the influence on the output signal of the converter due to variations in the characteristics of the transmitter on the converter side and ensure compatibility between the two. purpose. The present invention that achieves such a target sound is characterized by variations in the signal electromotive force generated on the transmitter side [Transmission II
By setting this constant in the converter, the converter side can change the amplification factor of the signal electromotive force or adjust the magnitude of the signal electromotive force to the constant. The point that correction is performed by adding the proportional value t#4 is the basis of the technical idea.The following is an example of the present invention. This will be explained in detail based on JFIiK. As shown in the figure, the transmitting IW1 includes an exciting coil 1,
Inner sea constant fluid conduit 2 and this conduit 2 are equipped with nine electrodes 3, 3at, constant voltage 1111114'
In the magnetic field formed by supplying the excitation coil IK to the excitation circuit and the excitation tube, the signal electromotive force generated between the electrodes 3.3a when the fixed fluid flows! On the other hand, the converter Otori converts the signal electromotive force tube impedance into a buffer amplifier 5.6, the output signal of this buffer amplifier 5.6 [preamplifier 7 to amplify, condenser tC1 for holding, and accumulation in this] The output signal of the preamplifier 7 has a switch 8W and Ili for discharging the electric charge, and an integrating circuit 8 for sampling and integrating the output signal of the preamplifier 7 intermittently.A variable resistor 1 as a feedback resistor.
) A variable gain amplifier 9 which can adjust the gain by using Rm and amplifies the integral 1 path $O output signal described in K11l, and a microcomputer MO which outputs the output signal tI & output signal of this variable gain amplifier 9 as a flow rate signal. Nail・
j! , a micro combinator MOa, an A/D converter 10 for converting the output value of the variable gain amplifier 9 to t-'/D, a microprocessor 11, a memory 12. The input/output boat 13, the shim conversion 5114 that converts the digital signal t processed by this miterrocomputer MO into a flow rate signal which is an analog signal and outputs it, the flow rate setting 1i15a that sets the span, and constants specific to the transmitter 1 are set. Meter constant setting 1B1! ! 1) Setting slB and handling of the variable gain amplifier 90 output signal from the data bus 16 and address bus 17 connected to each of these functional blocks.

Switch 5vzsv*lW at predetermined timing
m e lW4 @ Bah f intermittent sultodo 4hII
11 of the variable gain amplifier t*m according to the value set in c setting lll5. (“C Sweets? 814
m B'Wm0III! ] A constant short y# wave excitation current flows through the excitation coil IK, and the output signal of the preamplifier 70 is sampled by turning on and off the switch 8ux O, and the switch 8W10 reverses the operation.
It is detected by the current detection resistor due to the interruption of the amplifier 18.
The load current from the constant current 114 is sampled at . j! In this case, the span setting is set as the maximum flow velocity as in the prior art, while the specific constant of the transmitter 1 is the standard transmitter, i.e., the standard signal station power at a given flow rate when the standard excitation current is applied. The transmission generated by the tube is expressed as a ratio to this as ``O'', and the standard signal emf of a standard transmitter is . Signal electromotive force at [・t
-, then the specific IIR area specific to this transmission III is
a/. That is, the standard transmitter is the standard jlIiIlIIE#1'''e flow interrupter 1
-/@@60 When a signal electromotive force of 1 sV is generated, the general transmitter 1 has a flow rate of 4° with the same all current. When LO3111V011 electromotive force! If it happens, this message will be sent! 110 constant lc-In31/
1 = 11) 1. In such an electric a#l quantity needle, the converter 10 output car M(S
), span setting value of converter 1 (m speed 0 full scale) control ma (gA#), meter setting 11 (transmitter IK constant) -m K = m・ts/,,,, transmitter I [Real
If the regulated fluid O#1 is used as l1KfIL, then the signal electromotive force when the flow velocity is equal to the standard O transmitter (-sum) is... &) ■Ma 1-1 General transmission The signal electromotive force・t(→■ma・t−) when the flow velocity is low (-noise).

On the other hand, the converter 10 output mF is given by the linear equation ・1m・
i/iv (however, 1sIIm input value number) and the conversion 1sio output when combined with a standard oscillator is as follows.

M ” T, 66g7. (”:, Kam l,
@1 #・-に）1MA・1-)・・・■ On the other hand, the conversion lll0 when combined with -1R oscillator 1
The output M goes to the next 6jlj.・11@,,,Ma・・t+
I/@ts,y 3111 v,s51/v(a:,'
” @tll/,,, , @1 xm @@, (
y) ■V・t＠ )O・・■ 0 formula 8 @ 2〇 @ 呆
lIIIi will be done. That is, at the same time, the flow rate setting 1g15aK of the setting unit 1s of the converter 1 is set to the full scale flow rate, and the transmitter 1 combined with this is set to the meter constant setting 115b.
A constant specific to ! You can make both compatible by setting ・In addition, "-"i/x, v O operation is ・10 signals 't
There is a difference between the method of performing VD conversion and digital calculation after rounding, and the method of changing the gain of the variable gain amplifier 9 [by command of the microcomputer MO] as in the above embodiment. However, VD conversion
However, in the latter case, the resolution of the variable gain amplifier's 90-dyne setting is required, which makes it more complicated.Let's explain this in detail with the above examples. In fact, according to WAK, the signal electromotive force Q variation generated on the transmitter side is 11 and the transmitter is 0.
5@Measure each outgoing is* as a number and write this O constant at
By setting it in the converter, the converter side can perform correction by changing the amplification factor of the signal electromotive force or by matching the magnitude of the signal electromotive force with a value proportional to the constant. Therefore, the W/411 on the converter side can be compatible with the transmitter, and the associated work etc. can be facilitated.

[Brief explanation of the drawing]

The figure is a plotter diagram showing an electromagnetic flowmeter. In Figure Threshold, 1 line transmitter, 1 is a converter, 15tj setting section, 15bFi meter constant setting section. patent applicant Hokushin Electric Manufacturing Co., Ltd. Representative person Benmaroshi Party Ishishi Club (m1 people)

Claims (1)

[Claims] It has a transmitter, a converter, and an excitation coil Kt of the transmitter.
jIn an electromagnetic flowmeter to which a constant current is supplied, the ratio of the signal electromotive force generated by a standard generator at a standard excitation current and a predetermined oil speed to the signal electromotive force generated by the transmitter under the same zero condition. That message! Kll is a constant, and the constant is set in the converter, and the signal electromotive force input from the oscillator to the conversion amount is multiplied or divided by the constant and outputted. Electromagnetic flow needle.