GB2210698A

GB2210698A - Liquid density instrument

Info

Publication number: GB2210698A
Application number: GB8723370A
Authority: GB
Inventors: Malcolm Owen Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-10-06
Filing date: 1987-10-06
Publication date: 1989-06-14
Also published as: GB8723370D0

Abstract

Elements E1 and E2, of different weights but the same cross-sectional area are free to float vertically in a liquid under test by means of a guide frame 12 carried by a flotation body 13 floating on the surface of the liquid. The difference in immersion depths between the two elements is converted into an electronic signal e.g. by electric tracks 20 on the elements cooperating with contacts 21 and processed, together with an electronic signal indicating the temperature of the liquid under test, from temperature sensor 15, through electronic circuitry to provide a specific density or density, corrected to a reference temperature, in a digital display form. The digital display can be read on the instrument, or on an extension digital display some distance from the instrument application, or relayed to a transmitter for incorporation into a remote data processing system. <IMAGE>

Description

LIQUID DENSITY INSTRUMENT This invention relates to an instrument for immersion in a static liquid to determine the specific density or density of that liquid.

For stock control and quality control of liquids in storage tanks the specific density can be determined by the use of a hydrometer and thermometer applied to a sample of the liquid drawn from the tank. The specific density readings, so obtained, have to be corrected to a standard reference temperature using density/temperature conversion tables, and the liquid temperature at which the specific density was obtained.

Such determinations have to be done with care because of the fragile material of the hydrometer and thermometer, and with a degree of skill in taking readings at the surface level of the liquid. The determinations are also time consuming because of the need to correct the readings by reference to conversion tables and the results have then to be relayed through relatively slow channels of communication to be fed mannually into remote data processing systems.

The invention overcomes these drawbacks. Basically, as shown in drawing FIG. lA, the specific density of a liquid can be determined on a liquid sample 1 in a container 2 in the same way as a hydrometer and thermometer determination, by mounting the instrument on a stand 4. Tough materials can be used in the construction of the invention sd that it is robust in use.

Alternatively, with an extension lead 9 on the invention 3, as shown in drawing FIG 1B, the specific density can be determined on the liquid 5 in a storage tank 6 and the specific density read from an extension display 7, outside the tank, by an operator 8.

Alternatively, as shown in drawing FIG lC, by connecting the extension lead to an electronic signal transmitter the specific density display signal can be incorporated directly into a remote data processing system.

The invention is designed around the principle illustrated in drawing FIG 2, that if two elements of known but differing weights, W and Kw, of the same crosssectional area A, and of constant cross-sectional area, and of the same lengths L, are immersed in a liquid, so that they can move freely in a perpendicular plane only, then the density of the liquid is equal to the difference between the weights of the elements divided by the difference in their depths of immersion (H2 - H1) times the crossrsectional area A. If the weights of the elements are in grams and the dimensions are in centimetres then the density so calculated is also the specific density relative to water.

If the cross-sectional areas, lengths and weights of the elements are known, and the densities of the elements adjusted so that they will float when immersed in the range of liquids for which specific density determinations may be required, then the measwurement of the difference in immersion depths of the two elements can be used to determine the specific density or density in grams per cubic centimetre of any liquid in the range.

A specific embodiment of the invention will now be described by way of example with reference to the drawing FIG 3. This shows a section through the invention to illustrate the relevant parts which are: Two elements El and E2, of different weights but same cross-sectional area and length, which are free to move easily in the vertical plane, but constrained from moving in other planes by a guide assembly 12. In this example the guide is in the form of two vertical rods, but any form of constraint which allows free vertical movement of the elements El and E2 can be used.

A flotation frame 13, having a cavity 14 for electronic components and circuitry is designed to allow the invention to float upon the surface of the liquid under test 16, with suitable immersion levels for the elements El and E2 within the invention.

The flotation frame has provision also for an electronic temperature censor 15 to be immersed at a suitable level in the liquid under test.

A bottom cover 17, which can be made of transparent material, to protect the elements El and E2, and also to support the guide frame at its lower end. The cover is perforated to allow the liquid under test to enter the invention to displace the elements El and E2. The bottom plate of the guide frame 12 is also perforated to allow liquid to drain from the invention after testing.

The top end of the guide assembly is connected to an assembly box 18, which houses a digital display 28 and associated electronic components and circuitry.

The assembly box is connected to the flotation frame by means of a top cover 19 which can be made of transparent material. The top cover also supports the upper end of the guide assembly 12.

The different heights of the elements El and E2, when floating in a liquid under test, are measured by means of an electronic signal which varies in accordance with the distances displaced by the elements in the liquid. Any method of converting linear distance into electronic signal can be used for this purpose. In the example shown each element carries a linear electronic track 20 with contact points 21, so that when a voltage is applied to the track the voltage will vary in accordance with the distance of the resistance track above the contact points. The tracks and points are adjusted so that the difference in voltage between the two tracks varies in accordance with the difference in immersion depths of the two elements.

Provision is made for the contact points to be connected electronically to electronic circuitry in the cavity 14 of the flotation frame, and through conduit 22 for electronic connections to be made from the cavity 14 to the electronic circuitry in assembly box 18.

A hanger frame 23 is fixed to the assembly box and attached to the hanger frame is an extension frame 24.

Also attached is an extension cable 25 which has an extension mains electrical plug 26, and an extension plug 27 for remote reading of the digital display and for relaying the display signal and control signals to a transmitter as input to a remote data processing system.

The elements El and E2 are weighed in grams and the dimensions of the elements measured in centimetres so that the display shows the specific density as a number or the density in grams per cubic centimetre.

All the structural and working parts of the invention may be constructed fromotough durable materials, so that the instrument is robust in use.

A block diagram of the electrics-electronics is shown on drawing FIG-4. The invention can be powered either by battery or by mains electric supply. The electronic signals from the devices that convert linear distance into electronic signals and the device that converts temperature to electronic signals are fed to signal conditioners and then multiplexed through an analogue to digital converter to registers. From the registers the signals are translated through a ROM, programmed with density-temperature data, so that one of three digital output signals can be relayed to the instrument display, or to an extension display, or for transmission to a remote data processing system. The three output signals would display either the specific density or density of the liquid as measured, or the temperature of the liquid in which the density determination had been made, or the specific density or density of the liquid converted to a particular reference temperature.

A sequence and display controller is programmed to deliver any of the displays, either direct to the digital display on the instrument or to a remote display some distance from the instrument application, or to a transmitter for relay to a remote data processing system.

Additionally, provision is made for a signal to be generated in digital form, when the elements are positioned in a certain configuration, to set and calibrate the instrument display, or output, to the density reading for water at a standard temperature.

Claims

1. An instrument that utilises the difference between immersion levels, as measured above the surface of immersion, between two elements of the same cross sectional areas but of different weights, when immersed in a static liquid to indicate the specific density or density of that liquid.

2. An instrument as claimed in claim 1 wherein the difference in immersion levels between the two elements is measured by a device that converts linear distance into an electronic signal for translation by electronic circuitry into a digital display of the specific density or density as measured by the elements.

3. An instrument as claimed in claim 1 and claim 2 which -inccrporates a device to measure electronically the temperature of the liquid in which the two elements are immersed, at the time of immersion, for translation by electronic circuitry into a digital display of the temperature of the liquid.

4. An instrument as claimed in claim 1 , claim 2 and claim 3 which has electronic circuitry to combine the digital display signal of specific density or density, as measured, with the digital display signal of the temperature, in accordance with data in electronic form on specific density or density, and temperature relationships, to produce a digital display of density or specific density at a particular reference temperature.

5. An instrument as claimed in claim 1, claim 2, claim 3 and claim 4 which has provision for any of the digital display signals generated by the instrument to be relayed to an extension display, at a distance from the application of the instrument, or to be connected to a transmitter for relay to a remote data processing system.