The LPG Gas Monitoring Extension 

Gas Cylinder Load Cell
Gas Cylinder Load Cell

Because Liquefied Petroleum Gas is stored in a liquid state the pressure in the storage cylinder remains fairly constant, varying according to temperature and composition (the propane/butane mix ratio), rather than quantity. To determine the quantity of liquified gas remaining we have to weigh the cylinder including its contents, and then deduct the empty weight of the cylinder. The empty weight is always clearly marked by stamped figures on the support skirt of the cylinder.

Can be used with:

The LPG Gas weight monitor consists of a load cell with a maximum weight capacity of 50 Kgs that connects to the control unit through an A/D converter.
The load cell measures the total weight of the cylinder, and the gas it contains, and transmits this data to the control unit. 
The control unit corrects the input data with an internal offset and passes it on to the mobile phone app.
The mobile phone app subtracts the tare (empty weight) as entered by the user, and displays the balance, which is the weight of the gas, on the screen of the mobile phone.
The background colour of the display button will change with the weight of gas displayed:
Above 3 Kgs the background will be GREEN,
Between 1,6 Kgs and 2,9 Kgs the colour will be YELLOW,
Below 1,6 Kgs the colour will be RED.

First Use

After installation the load cell's no-load output must be registered in the controller as a zero datum. This needs only be done when a load cell is connected the first time and is accomplished by double tapping the Gas button on the screen of the mobile phone when there is no weight on the load cell. The phone will buzz briefly and the weight display will go to 0 Kgs, if it is not already doing so. The updated weight info can take a few seconds to be shown. 

Entering the Tare on the Mobile App

The weight shown in the Gas Weight button will always be the weight measured by the load cell minus the Tare, or empty weight, of the cylinder as stored in the app's memory. If the total weight detected by the load cell is 3,6Kgs and the Tare is recorded as 1,2Kgs then the display button will show 2,4Kgs. If you want to display the full weight borne by the load cell the Tare must be set to 0'

To enter the Tare on the mobile app tap the Gas Weight icon on the left of the screen once and within 3 seconds double tap the Caravan Pilot Title.

Setting the TARE
Setting the TARE

Setting Up the Tare.

After tapping the Gas icon on the left of the screen, within 3 seconds double tap the Caravan Pilot Title. A slide control will appear showing the last value of this setting that has been entered. Move the slider to the correct value (max 20 Kgs) as stamped on the gas cylinder added to the estimated weight of the regulator and supported hose, and tap the Title line again to Save.
The Gas button will now display the measured weight of the cylinder with the Tare subtracted. The Saved value will endure until changed.

If the weight displayed is 3kgs or more the background colour of the button will be GREEN. Between 1,5Kgs and 2.9Kgs the button background colour will be YELLOW, and below 1,5Kgs the background colour will be RED.

Peeking the Parameters

Tapping the Gas 1, Gas 2, or Towball weight button once, will briefly reveal the Tare(s), GVM, and Correction Factor that have are stored for the button being tapped, in place of the normal button information display. This is a convenient method of quickly confirming that the correct values have been stored.

Installing the Gas Cylinder Load Cell

The load cell must be placed under the centre of the gas cylinder such that the centre of the bowl rests on the load button of the load cell with its entire weight. If the gas cylinder is able to move around it must be restrained from doing so without assuming any of the cylinder's weight burden. If the gas cylinder is held in a clamp the clamp must be loosened sufficiently that the entire weight of the gas cylinder rests on the raised button of the load cell. The full weight of the gas cylinder (but only the gas cylinder) must be freely and centrally sustained by the sensor. If any part of the cylinder's weight rests anywhere other than on the button of the load cell incorrect weight will be recorded and displayed.

There are a huge variety of gas cylinders available on the market and no two installations are identical. Therefore every sensor installation will be to some extent unique, and a degree of ingenuity will be required to optimise the effectiveness and reliability of the said installation.  If unexpected gas weight readings appear on the phone the correct placement of the sensor under the cylinder should be checked first.

The load cell is supplied in it's simplest and hence most versatile form from which it can be mounted on any pedestal suited to the specific needs of the installation.
The A/D converter, which is housed in a plastic enclosure a half a metre from the load cell should be mounted on a wall where it will not be damaged using the mounting tape supplied. From the A/D converter there is a 4 metre cable terminated in a 4-pin XLR plug which plugs into a socket on the control unit housing. The socket is clearly marked 'Gas'.

There are always a few seconds of delay between the controller receiving fresh data from the load cell, and that data being displayed on the screen.

Dual Gas Bottles

If only a single gas cylinder is in use at any one time and a selector valve switches between cylinders the load cell can be physically positioned under the active bottle.  When the gas selector valve is switched to the second cylinder the load cell can also be moved to take its place under the now-active cylinder. It may be necessary to revise the Tare weight of this cylinder to keep the gas-content information accurate.

When 2 LPG gas cylinders are to be monitored simultaneously the controller may be connected to 2 LPG load cells (in addition to the optional Tow Ball load cell). The Tow Ball Weight button doubles as a control and display button for the second LPG cylinder. In this case both gas weights are simultaneously displayed on the mobile phone screen, except when the right-hand weight button doubles as the tow-ball weight display.

To convert the right-hand weight button to monitor Gas 2 press the Tow Ball button down for at least 5 seconds. The legend on the button will change to Gas 2, and usual Calibrate command and Tare setup becomes operational.

When the tow ball is to be weighed simply hold the Gas 2 button down for 5 seconds and the button will revert to Tow Ball weight measurement.



Load cell for measuring LPG gas cylinders weight
Including A/D Converter, 4 metres cable and 4-pin connectors XLR.   each (Max 2)             R200
 Shipping is usually with a control unit, which is free via PostNet