1 principle of electromagnetic flowmeter

E = DVB (V) (1) is based on the basic law of magnetic effect of current, that is, when a flowmeter calculation formula exercises in the magnetic field, and the orientation of exercise is perpendicular to the bisector magnetic field, it will immediately cause induced current, resulting in the orientation of induced current perpendicular to the bisector conductor exercise and the orientation of magnetic field exercise, The size of the induced current is directly proportional to the fitness movement speed of the electric conductor and the magnetic induction intensity of the electromagnetic field. When the average water flow V (M / s) of conductive fluid mechanics is based on a water pipe with a nominal diameter of D (m), if there is an electromagnetic field with a magnetic induction intensity of B (T) in the water pipe, then it can cause an electromotive force E that is perpendicular to the bisector magnetic field direction and the fluidity direction of fluid mechanics

Capacity flow Q is:

Q=πD2V/4 (m3/s)(2)

Substituting formula (2) into formula (1) and solving the problem:

E=(4B/πD)×Q (V)(3)

If B and D are constants, then it can be seen from formula (3), e and

Q is proportional. The EMF e is enlarged and transformed into a standard 4 ~ 50mA data signal or differential signal, which is used as the matched flow data signal output.

2. Basic parameter mode and configuration of gas flowmeter

2.1 the common marks on the electromagnetic flowmeter control panel of admagae series products for setting the main parameters by using the control panel are: there are two ways for the basic parameters (configuration) of the flowmeter, one is to use the function key on the display information control panel, the other is to use the hand-held mobile intelligent terminal.

(1) Red (red) does not light up when all are in normal operation, and flashes when there is an alarm;

(2) The definer definer uses the cooker ':' to express the data information of the displayed information which is in the situation to be set;

(3) Enterprise display information display information flow enterprise;

(4) Display information data information display information flow data information, set data information and alarm type;

(5) Decimal places represent the decimal places in data information;

(6) Set key this key is used to change the data information display information and set the type of data information. There are 3 kinds of data information display information: flow data information display information mode, setting mode, alarm display information mode.

2.1.1 flow data information display information mode

Admagae can display 12 kinds of traffic data information. The main parameter of "D1" is used to change the display information item. For detailed setting, please refer to the flow calculation.

2.1.2 setting mode

2.1.3 the setting mode of alarm display information is used to check the main parameter content and rewrite the data information. If you press the "SET" button, it can be adjusted from all normal operations.

When the alarm is generated, the alarm mode will immediately replace the current mode to display the type of alarm generated by information, but this kind of situation only occurs when the main parameter number in the current flow display information mode or setting mode is changed (when the data item has already been set, the alarm cannot be displayed).

2.2 setting of BT mobile intelligent terminal

The instrument panel with intelligent communication function can communicate with the mobile intelligent terminal. Yokogawa mobile intelligent terminal has Bt100, BT200 and other model specifications, commonly known as BT mobile intelligent terminal. They select brain protocol, and add a ± 1mA, 2.4khz deployment data signal to 4-50ma digital signal as data signal transmission. Because the deployment data signal is the communication and exchange data signal, it is not easy to damage the value of the digital signal.

There are two ways to connect BT mobile intelligent terminal and flowmeter: one is to connect it immediately with BT terminal under the bearing end cover of flowmeter, which is suitable for on-site adjustment or the flowmeter does not have intelligent communication function; the other is to connect it with 4-50ma DC power line, and BT mobile intelligent terminal can be connected to all parts from the control box to the power line of flowmeter, with a large distance of 2km, If the load resistance of all control circuits is between 250 and 750 ψ, reliable communication can be achieved. Operators of this kind of method can set and monitor the flowmeter online in the main control room without going to the spot. It is a method with many applications. BT mobile intelligent terminal selects Laishan type practical operation, which can display information and change all kinds of main parameters of electromagnetic flowmeter anytime and anywhere. Its basic practical operation includes flowmeter self-examination, measurement range adjustment, dynamic display setting, alarm setting, etc.

2.3 data information setting and configuration of electromagnetic flowmeter

The electromagnetic flowmeter is based on the micro electromotive force measurement corresponding to the hydrodynamics water flow to calculate the volume flow and output 4-50ma data signal. In order to ensure the proper data signal, it is necessary to set three main parameters: pipe diameter, flow measurement range and instrument panel index. Of these three main parameters, the pipe diameter and instrument panel index have been set before the original factory of instrument panel, so the customer cannot set these two main parameters. The customer can also set the flow measurement range before the original factory of the instrument panel. Such setting can only be set again when the customer specifies to change the measurement range.

Analysis of EMC test

In the operation of electromagnetic flowmeter, the basic law of magnetic effect of current is taken as the basic law. The induced current which is directly proportional to the measured flow is generally small, and it is very easy to suffer from external electromagnetic induction interference, while the electromagnetic induction interference caused by itself is small, Therefore, the key of EMC test of electromagnetic flowmeter is how it works normally in the extreme electromagnetic induction natural environment. In the extreme environment of electromagnetic induction, the discharge at the coupling tip of electromagnetic induction is the key source of interference noise of electromagnetic flowmeter