Measuring and testing – Volume or rate of flow – Using rotating member with particular electrical output or...
Patent
1997-12-10
1999-10-12
Patel, Harshad
Measuring and testing
Volume or rate of flow
Using rotating member with particular electrical output or...
222 71, 25023118, 32420722, 324174, 324175, G01F 1500, G01D 534, G01P 336, G01B 714
Patent
active
059658258
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a pulse encoder for fitting to the meter of a liquid dispenser device in order to deliver a signal representative of the flow of dispensed liquid.
A particularly advantageous application of the invention lies in the field of dispensing fuel.
Below in this text, the general term "meter" is used without distinction both for volume meters and for flow rate meters, it being understood that in the first case the signal representative of the dispensed liquid flow is a volume signal that enables the volume of liquid dispensed to be calculated by summing the pulses, whereas in the second case, said signal representative of the dispensed liquid flow is a flow rate signal enabling the volume of liquid dispensed to be calculated by integrating a pulse frequency.
BACKGROUND OF THE INVENTION
By way of example, fuel-pump meters in a fuel dispensing station usually comprise a pump enabling said fuel to be brought from a storage tank to a delivery point, in this case the tank of a vehicle, by passing through a volume meter or measurer whose function, in quite general terms, is to produce rotary motion from the flow of fuel in such a manner that one complete revolution corresponds to a known given volume of fuel passing through the meter.
An encoding system coupled to said rotary motion in association with the volume meter forms measurement apparatus suitable for forming a signal representative of the volume flow of fuel that had been dispensed, which signal is processed by a computer designed to sum the volume signal received from the encoding system so as to be able to determine the volume of fuel dispensed by the fuel-pump meter in question, and also the amount that needs to be paid, given the price per liter of fuel.
This information is then displayed to the customer on a display incorporated in the corresponding fuel pump meter.
The encoding systems most commonly used are pulse encoders suitable for delivering an electrical signal constituted by a series of pulses, each of which corresponds to the volume increment at which the volume of fuel dispensed is measured, e.g. 1 cl.
In principle, a pulse encoder comprises a coding wheel mechanically coupled to the meter and thus driven by the meter at a speed of rotation that is substantially proportional to the flow rate of the liquid. Said coding wheel carries a series of divisions, e.g. on its periphery, which in one particular embodiment may be constituted merely by slots of angular period P corresponding to said measurement volume increment.
While the coding wheel is rotating, a single sensor, e.g. an optical sensor, disposed to be able to detect the passage of said slots then provides a pulse signal that is representative of the volume flow of liquid dispensed.
This signal is sent to the computer which then establishes the volume of liquid dispensed by multiplying the total number of pulses received by the volume measurement increment.
Nevertheless, that type of known pulse encoder suffers from several drawbacks.
Firstly, it does not enable the direction of rotation of the flow meter to be defined. It is therefore not possible to detect when the direction of rotation is reversed, e.g. due to hydraulic hammer, and as a result, the encoder continues to deliver pulses even when the rotation of the coding wheel is in reverse and no volume of liquid is flowing. Since these interference pulses are taken into account by the computer along with the others, this results in an overestimate of the volume of liquid dispensed.
Also, during small-amplitude oscillations of the meter, it can happen that the level of the signal provided by the sensor remains constant, i.e. at a high level if the sensor remains in register with a slot, or at a low level if the sensor remains in register with a land between two consecutive slots. However, a low level can also be due to a fault in the sensor itself, so it is not possible with that type of encoder to distinguish between the phenomenon of small oscillations and the sensor being out
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Knuth Randall J.
Patel Harshad
Solutions Services Systems France S.A.
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