The instrument sends an ultrasonic signal. The transmission and reception of the signal through the pipe wall and interior fluid are performed through a piezoelectric ultrasonic probe and then transmitted through the ultrasonic signal. The resulting time differential is used to measure the flow. The distance between probes must be precisely calculated and the probes must be correctly placed to ensure measurement accuracy. This section describes the relevant wiring and installation precautions.
Generally, the probe should be set up using a V or Z configuration. A small number of specific applications may require an N or W configuration. The four configurations are described below:
● V configuration: In general, tubing with a diameter of 50 ~ 300 millimeters takes this configuration. The two probes are mounted on the same side of the tubing, with the resulting ultrasound signal having a V-shaped bounce. Because the probes are on the same side, it is easier to measure the distance between probes, and because the ultrasound only reflects once, a balanced signal strength is achieved.
● Z configuration: Generally used in diameters of more than 300 millimeters, the ultrasonic signal is not reflected, thus helping to maintain signal strength. This helps avoid a weak or distorted signal. However, because the probes are mounted diagonally on opposite sides of the tube, measuring the probe distance is more difficult.
● N configuration Generally used in tubing of less than 50 millimeters, the probes are mounted diagonally on opposite sides of the tube, making it more difficult to measure the distance between them. The ultrasonic signal is reflected two times, making three paths, and thus increasing signal flight time and enhancing measurement accuracy in thin-diameter pipes. This method is only recommended if the V configuration cannot be adjusted to produce the ideal signal state.
● W configuration Generally used in tubing of less than 50 millimeters, the ultrasonic signal is reflected three times, making four paths, and thus extending signal flight time. There are cases when this method can improve measurement accuracy for small tubes. This configuration makes measuring probe distance easier than the N configuration does, because the probes are mounted on the same side of the tubing, but it is not recommended unless it is otherwise impossible to attain the ideal signal state.
● Pipeline Installation Location Liquid flow in the pipe will be obstructed by bends and other forms of obstacle. In order to ensure flow measurement precision, probes should be installed in such a manner as to avoid confusion in the flow field. The following table shows a variety of common pipeline configurations, and the corresponding upstream and downstream probe recommendations. The installation location for the upstream and downstream probes should correspond as much as possible to the positions recommended in the table (select the situation that most closely meets actual site conditions).
● Probe distance calculation Set the initial value of each parameter in the meter setup. After setting the values, find the probe spacing item in the initial value menu. After the values have been entered, this will display the probe distance calculation results. Please set up the probe in accordance with this distance. Setup accuracy will directly affect the accuracy of the measurement results. It is recommended that adjust TOM/TOS to 99.90%~100.10%
The probe should be installed on the side of the pipe in order to avoid cavities produced by gases accumulated at the top of the pipe that affect the transmission and reception of ultrasonic signals. If the probe cannot be installed on the side, it is important to ensure that the pipe is filled with fluid at all times. Any gap between the probe and the tube walls will result in substantial attenuation of signal intensity, seriously affecting signal strength and quality. Therefore, a coupling agent must be applied between the head of the probe and the tube wall during installation to ensure that no air bubbles remain between the probe and the tube wall.
The accuracy of an ultrasonic flowmeter is mostly determined by correct probe installation. If the installation method or location is incorrect, it may result in failure to achieve the desired results, or even an inability to send and receive ultrasonic signals. In general the conditions for the best installation location are as follows:
● It is better to mount the ultrasonic probe on a longer tube or pipe; be sure to verify that the pipe is filled with liquid.
● Installing the probe on the side of the pipe can reduce bubbles and interference caused by partially empty tube cavities.
● Make sure the probe can withstand the temperature of the measuring point; the closer it is to room temperature, the better.
● There are linings on the inner walls of some pipes. Though this product can be configured to be compatible with lined tubing, in practice this inner layer tends to block the transmission of ultrasound and thus the measurement results, so install as far as possible from this type of tubing.
Correct probe installation will greatly enhance measurement accuracy.
Each probe has three wires, so there are six contacts on the meter as shown below. Install the probe in the order shown in the figure below. If the probe model has no ground connections, it is okay to only install the positive and negative contacts.
This product deals with ultrasonic signals in a differential manner. Therefore, probe wiring must include "Signal ㊉", "Signal ㊀" and "Ground Isolation ". Use 2-core cable (2C) with a grid structure, outside diameter (OD) of less than 7 millimeters, conductor cross-section of 0.5-0.75 mm2 , with a total length of less than 10 meters, so as to avoid signal attenuation caused by poor measurement quality. In addition, the upstream and downstream probe wire length must be consistent to avoid transmission error. The wiring method is as shown below:
After removing the cover, Erminals can be seen inside: "Signal ㊉", "Signal ㊀" and "Ground Isolation " . Secure the wires through the waterproof packing head to the corresponding terminals in the sequence shown below.
Before replacing the cover, it may be advisable to reinforce the waterproof features of the cover by screwing, gluing, etc., as shown by the dotted line on the figure below-left. After covering, screw the cover on tightly to complete the probe wiring procedure.
<Reference: Wiring essentials>
1.The quality of the wiring will affect ultrasound signal quality and measurement accuracy. It is important to install the wiring correctly and securely.
2.After cutting the length of wire required, first pass one side of the head through the waterproof packing head of the probe and then peel off the 40-millimeter insulation layers on both sides. Finish the insulation layer as shown in the figure below.
3.Separate the jacket with a corresponding 35-millimeter heat shrink sleeve and a 20-millimeter heat shrink sleeve on the outer circumference of the cable. Heat to fasten, then clip the Y-shaped terminal.
4.Secure each terminal of the probe in the correct position, as shown in the following figure. Tighten and fix the wires, then glue the probe cover shut as described in the previous section. (If there is further need for waterproofing, waterproof resins or rubbers can be used to fill in the space.
5.Equipped the other end of the wire with a corresponding 35 millimeter heat shrink sleeve on the isolation layer, and a 20 millimeter heat shrink sleeve on the outer side of the cable. Heat to fasten, and then clip the European style terminal to complete as shown below.
