FR2508636A1 - Electric fluid flowmeter and calibration method - has rotor casing provided with supplementary orifices to provisionally receive electrodes measuring flow by conductivity during calibration - Google Patents

Abstract

The process uses a rotation detector with electrodes to calibrate a conductive liquid meter, e.g. a water meter. This process can be used when the liquid meter (90) is of the multiple jet type and contains an electrically insulating rotor (93) inside an electrically insulating injection casing (91). To use this process, two additional holes (92) are placed in the injection casing (91), opposite one (94) of the meter's tubes. During calibration, two pins (97) are temporarily inserted into these holes (92). These pins (97) are used as electrodes for the detector (99). This detector (99) deduces the flow rate measured by the meter by detecting the periodic variations of the electrical resistance of the liquid between the electrodes (97). These variations are produced by the rotation of the rotor (93).

Description

Pulse emitter flow meter for conductive fluids and application to meter calibration.

The present invention relates to the measurement of flow rate of conductive fluids, and more particularly to the calibration of liquid meters equipped with an emitter of electrical pulses with electrodes.

In the initial application, a flow meter emitting electrical pulses for an electrically conductive fluid has been described in which a rotor with blades of electrically insulating material is mounted to be rotated at a speed which is a function of the flow rate of the fluid to be measured, and which comprises - two isolated electrodes arranged in the vicinity of the step-
wise rotor blades and connected, in
operation, to a source of electrical potential
so that the rotation of the blades produces
periodic variations in the electrical resistance of the
fluid between the two electrodes, and - detection means and means for counting the
say periodic-resistance variations.

The invention provides for the temporary adaptation of such a rotation detector to calibrate conductive liquid meters by taking advantage of the conductivity of the fluid to detect the rotational movements of the electrically insulating rotor.

According to the invention, the use of an electrode rotation detector for the calibration of meters of conductive liquid of the multiple jet type comprising a rotor of electrically insulating material rotating in an injection box of electrically insulating material, is characterized in that provision is made to pierce two additional orifices in the injection box opposite one of the meter pipes, these two orifices being intended to temporarily receive, during the calibration of the counter, two pins playing the role of electrodes connected to detection and counting means to deduce the flow rate measured by the meter by detecting periodic variations in the electrical resistance of the liquid between said pins caused by the rotation of the rotor.

More particularly, the invention relates to water meters known as speedometers whose turbine is by construction, according to current technology, most often made of insulating plastic material. The resistivity of the water being of the order of 2 to 3000 SI. cm, it suffices to have two electrodes passing through the injection box made of electrically insulating material near the passage of the turbine blades of the meter turbine, to collect on two wires connected to these electrodes periodic variations in electrical resistance at a frequency proportional to the speed of rotation of the rotor, that is to say the flow rate. Indeed, the sheet of conductive liquid located between the electrodes has a variable geometry with the relative position of the blades of the insulating turbine. Like these blades, the number of
N, are regularly distributed on the turbine shaft, the electrical resistance R measured between the two electrodes is the same for all the angular positions of the turbine spaced by 2 T? /NOT. The modulation relative to R / R is also independent of the resistivity of the fluid, and all the greater as the insulating blades of the turbine more completely mask one electrode with respect to the other. It was thus possible to obtain variations ss R / R of the order of 5 to 30% depending on the embodiment adopted.

A circuit for processing the electrical signals collected between the electrodes described in the initial request makes it possible to convert the periodic resistance variations into pulses which can be sent to a remote totalizer.

The invention essentially aims to reduce the calibration time of multi-jet water meters in which the first needle of the totalizer rotates at slow speed due to the significant reduction gear inserted between it and the shaft of the turbine of the counter. By providing for the temporary adaptation, during calibration, of an electrode rotation detector directly on the turbine of the meter, it is possible to reduce the calibration time in a significant ratio.

The invention will be better understood by referring to the description which follows in relation to the appended drawing which represents, by way of nonlimiting examples, an example of use in accordance with the invention applied to the calibration of a multijet counter.

The invention applies to the calibration of water meters with multiple jets, and in particular of meters with dry totalizer, but of which a significant part of the mechanical reduction controlling this totalizer is drowned in the liquid so that the shaft of output which attacks the first needle of the totalizer through a cable gland has sufficient torque. As a result, in this type of counter, the first needle rotates at low speed, even at high flow rates, and therefore the calibration takes a very long time. The use of an electrode rotation detector makes it possible to take the information on the number of revolutions directly on the turbine itself, which rotates at a speed in a ratio much higher than that of the first needle of the totalizer, and therefore reduce the calibration time of the counter in the same report.

To this end, provision is made, as shown diagrammatically in the figure, to pierce in the injection box 91 of the counter 90 two small additional orifices 92 spaced a few millimeters apart (but only one of which is visible in the profile view of the figure). ) in a plane perpendicular to the axis of the turbine 93 opposite, for example, the outlet pipe 94 of the meter. A rod 95 contains two insulated conductors 96 ending in two metal pins 97 which act as electrodes and which can be introduced into the orifices 92 to detect the rotation of the turbine 93. These conductors 96 pass tightly through a sleeve 98 making it possible to connect the outlet of the counter to the discharge of the liquid by a hose, and are connected to a circuit 90 for processing and counting the electrical signals detected by the electrodes 97.

During calibration, it is therefore easy to introduce the electrodes 97 into their housing 92 through the tubing 94, then mount the sleeve 98 on the tubing 94 and proceed to calibrate the counter by adjusting the screw. - usual needle. Once this operation is complete, the sleeve 98 with the rod 95 and the electrodes 97 are removed, and the counter 90 ready for normal operation under the usual conditions.

Of course, the invention is not limited to the single embodiment which has been described by way of example.

In particular, the electrodes are not necessarily arranged in a privileged position symmetrically with respect to a diametral or transverse plane to the axis of the measurer, but can occupy any positions, the passage of the rotor blades producing in all cases a modulation detectable and representative of its rotation.

Claims (1)

 CLAIM Use of an electrode rotation detector for calibrating meters of conductive liquid of the multi-jet type comprising a rotor of electrically insulating material rotating in an injection box of electrically insulating material, characterized in that it is provided to drill two additional holes in the injection box opposite one of the meter pipes, these two holes being intended to temporarily receive, during the calibration of the meter, two pins playing the role of electrodes connected to means detection and counting to deduce the flow rate measured by the meter by detecting periodic variations in the electrical resistance of the liquid between said pins caused by the rotation of the rotor.